The state has also ruled in favor of landowners in land disputes in Portuguesa

The Chavista governor of Portuguesa Antonio Muñoz reportedly stopped land invasions and maintained good relationships with grower associations in the state . Under Muñoz’s successor, Wilmar Castro, growers and state officials reported that land invasions by peasants and state intervention on estates increased . In general, however, producer associations stated that they maintained non-conflictive working relations with state institutions . ASOPORTUGUESA, for example, collaborated on a number of seed and crop research programs with the National Institute of Agricultural Research throughout the Chavista period. More importantly, broader agro-food policy continued to evolve in the Chavista period in a way that tended to shield a large number of commercial growers from expropriation. As the government became increasingly concerned about food availability it largely avoided intervention in commercial cereal or oilseeds producers. INTI officials in Portuguesa stated that as a matter of policy, productive farms were not targets for redistribution in order to ensure agricultural production . Even some activist peasants in the reform sector articulated a similar position that if land was in production campesinos considered it off the table for occupation. In Yaracuy state, for example, where conflict over land has been particularly pointed and conflictive, one peasant leader who himself had helped to occupy an estate said large landowners who were productive were ‘welcome’ . Through the Chavista period,dutch bucket hydroponic state agro-food policy became increasingly focused on maintaining the productive base for domestic provisioning and distribution of foodstuffs and less on the breaking up of historic land relations in rural areas.

Where the state has accelerated and widened its intervention in the agriculture sector has been primarily in marketing and distribution components of the food system or in particular crops such as coffee. Figure 20 shows acceleration of expropriation in the food sector beginning in 2009. These expropriations, however, can be read as part of a broader state strategy to ensure agricultural production and food distribution chains, rather than attempts to dismantle landholder power. The Venezuelan government, for example, nationalized major coffee companies Fama de America and Café Madrid in 2009 as part of a strategy to increase control over the distribution and processing of coffee and ensure its availability in state food distribution networks. Expropriations of the supermarket chains Éxito and Cada, and of agro-chemical company AgroIsleña, targeted not landowners, but up and downstream components of the agro-food system to support production at the farm level of all sectors of agriculture and, again, food availability at the market level. In addition, since 2003 the Chavista government sought strategic, unofficial ‘alliances’ with business interests that were considered important to the nation’s economic development . After the 2002-2003 oil strike promoted by FEDECAMARAS, the Chávez government declared it would favor non-striking business interests by providing them with access to dollars for imports at preferential rates Such concessions demonstrate a strategy of reconciliation between the capitalist sectors and the state in order to ensure macroeconomic stability. In Portuguesa, patterns of land occupation by peasants and government intervention in estates by and large circumvented the major cereal and oilseeds producers that formed the backbone of the state’s agricultural economy.

Growers did state, however, that as a preventative measure to land occupation by peasants they often planted ‘holding crops’ on land that were not harvested due to their general unprofitability—such as beans . An INTI representative in Portuguesa stated that when land occupations on estates did occur, the local INTI office declared them as illegitimate and withheld support from the occupiers including inspections and any granting of official rights to remain on the land .Where there was significant state intervention in private estates it was primarily related to continued conflict over timber plantations owned by the transnational packaging corporation Smurfit and in areas devoted principally to extensive cattle ranching. Most peasant occupations in Portuguesa during this study’s field periods were concentrated in these tree farms near the agro-industrial core and in cattle ranching areas that were located more on the state’s agrarian periphery. The peripheral lands—such as in the municipality of Guanarito—were relatively distant from major infrastructure, had inferior soils to those in the agribusiness core, were less likely to have mechanized production systems, and were less integrated into agro-food processing chains. Parcels in Guanarito were more likely to be perceived as idle and, thus, scenes of peasant occupation and state intervention. The Dos Caminos estate seized by INTI—one of the cases cited by local growers as indicative of government pressure on productive, private land in the state—was primarily involved in cattle and dairy operations, not cereal or oilseeds production . A land occupation at the San Rafael de Onote estate was ruled illegal in 2012 on the grounds that the estate was productive due to its maize and porcine production . That same year the Supreme Court reversed an initial ruling against the owners of the Palo Gordo estate after it was declared to be productive.

These cases reinforce the argument that cereal producers were not subject to significant land expropriation pressures. In a general policy climate of ensuring staple foods, the agro-industrial core of cereal and oilseeds producers appeared to be under relatively little threat of land seizure from the government. This is not to disregard the role of peasant pressure in influencing targets of government intervention in land and the shape and pace of land redistribution28 but rather to suggest that the major thrust of land redistribution has not been directed at sectors of commercial producers even in areas where they control a majority of the best and most productive lands. Landowners have used violence and intimidation in the reform period to fight against the agrarian reform. According to peasant groups, between 2003 and 2011, an estimated 256 campesinos were killed , likely by hired gunmen. According to campesino groups, no one has been convicted of any of the killings . That no landowner has been convicted of a peasant murder demonstrates the persistence of latifundio influence both regionally and in the judicial system where the deaths are investigated and prosecuted. This is despite nominal control of the judiciary by the Chavista political party, PSUV. Peasant groups have, thus, had to contend with the threat of violence when organizing for land. Land reform-related violence against peasants—as can be seen in Table 8—has largely been concentrated in four or five states within Venezuela. Portuguesa ranks as the state with the 4th highest number of peasant murders. Relevant to this dissertation’s argument, deaths were not common in the main agroindustrial areas of Portuguesa. The bulk of killings in Portuguesa occurred in Guanare and Guanarito municipalities .

Guanarito, as discussed, is an area home to relatively extensive dairy farmers that held more idle land than other areas where cereal and oilseeds production is integrated into agro-industrial chains. Peasant occupations that occurred primarily in Guanarito and nearby geographically and economically isolated areas engendered more violent responses. That commercial farmers in the agro-industrial corridor faced less occupation pressure underscores their relatively ‘safer’ position in terms of land redistribution pressures. Landed interests can also leverage their position as employers in land conflicts to blunt and fragment peasant pressure for state intervention. The case of Smurfit Kappa is an instructive example. Beginning in the 1980s, Smurfit began toacquire and operate tree plantations eventually totaling 31,000 hectares of Caribbean Pine and Eucalyptus in Portuguesa and Lara states . Smurfit’s expansion precipitated conflicts with peasants as farmers lost land or retained only limited access to areas that were surrounded by newly fenced tree plantations. In addition, there were a series of conflicts between managers and workers over working conditions and benefits. Conflict between Smurfit and peasants has continued throughout the Chavista era and has been heightened by the redistributive possibilities represented by the 2001 Land Law and increasing petitions for land and peasant occupations of some tree plantation areas. Relations between Smurfit, the state,dutch buckets system and peasant groups that this conflict has engendered is explored more thoroughly in the following chapter. The relevant point at this juncture is the dual strategy Smurfit has taken in order to diminish historical and resurgent peasant pressure. On one hand Smurfit has ceded certain parcels that INTI has classified as apt for crop production to the state in exchange for retaining ownership of other plantation areas.

This includes pre-Chavista negotiation where Smurfit gave up the 2,000 ha estate La Productora—which later became a co-managed Unit of Socialist Production in 2008—as well as more recent acquiescing to INTI inspections and redistribution of land to agrarian reform groups under the understanding Smurfit would be able harvest the timber before ceding control as well as receive indemnification from the state . On the other hand, over time Smurfit improved pay and benefits for workers, including providing scholarships to families of estate employees, which have became important subsidies for local households . Much of these benefits were won by workers after violent labor struggles that predate the Chavista era. These historical gains in labor conditions have contributed to Smurfit workers opposing peasant groups occupying Smurfit plantation areas, although both groups actively identify as government supporters. In 2012, I saw signs placed by Smurfit’s workers’ union along Portuguesa’s main highway reading “We are not exploited” and “We are also the revolution” to counter arguments that the seizure of Smurfit’s plantations would address exploitative labor relations as part of the Chavista socialist revolution. Smurfit workers saw peasant calls for land as threatening their relatively well-paid jobs whose benefits they obtained via hard-fought labor struggles. As part of the agrarian reform union members had been offered land they currently worked on as Smurfit employees, but stated that as laborers they received greater and more secure benefits than they could obtain as farmers on recovered plantation land . Workers cited an impression of general improductivity of agrarian reform settlements in the area, as well as the unreliability of state institutions that provided support to settlements . In response to threats of nationalization, the union negotiated its own proposal with Smurfit to cede certain parcels to the state in exchange for retention of core lands and then delivered the proposal itself to INTI officials . Essentially, the Chavista workers’ union negotiated with the state on Smurfit’s behest in order to constrain peasant land claims. This effectively fragmented the Chavista base’s stated position on land reform in the area. Reading dynamics between the state and the commercial sector as uniformly antagonistic and combative glosses over a series of more ambivalent relations. Violence against peasants, although significant, has largely been isolated to a relatively few areas of historical land conflict where peasant organizations have pushed for occupation of estates. State expropriation of land holdings has primarily been limited to areas of extensive cattle ranching rather than commercial commodity crop production . And while expropriations of supermarkets and large cattle estates have been featured in media headlines, these nationalizations have often targeted foreign, not domestic capital— the supermarket chain Éxito, for example, was owned by a French company—and land seizures are often negotiated with landowners, leaving large parts of estates, most likely the most productive and profitable areas, with the previous owners. In addition, commercial cereal producers in Portuguesa have faced relatively little risk of land redistribution even in areas that are highly Chavista. State intervention and peasant pressure in Portuguesa has instead been concentrated in cattle ranching areas on the peripheries of the state or in areas with foreign-owned tree plantations. As issues of food prices and availability in supermarkets serve as salient electoral weaknesses of the ruling party, combative rhetoric and threats of intervention of food processors take place in a wider policy context that seeks to incentivize production in all sectors of agriculture. I now move to discuss how certain Chavista agro-food policies contribute to accumulation in the commercial agriculture sector, even as state rhetoric maintains a pro-poor and pro-peasant character. To support agricultural production, the Chavista government in 2001 reasserted lending requirements of commercial banks to the agriculture sector. The Ministry of Agriculture and the Ministry of Finance are tasked with setting the percentage that commercial banks must lend to agriculture each year or face sanction. The amount required is set by the central government through the Committee for Monitoring the Agrarian Portfolio . The mandated percentage fluctuates from month to month but in general there is a 20-25% target, with a ceiling of 30% .Commercial banks have largely failed to meet the mandated lending targets .

A growing number of crops are being genetically modified to increase insect resistance

Conventional growers can use a pesticide spray on the trap crops, but that’s not an option for organic growers. However, tractor-mounted vacuum units known as “bug vacs” are one of the tools available for organic systems. “I worked on research of the original proprietary bug vacs for the strawberry industry back in the late 1980s,” recalls Swezey. “But back then we were using more of a shotgun approach, vacuuming all of the crop fields, which in a way was equivalent to using a pesticide because it affected all the insects in the fields—both pests and beneficials. This seemed to me to be as non-selective as an insecticide application.” Swezey and Larry Eddings, president of Pacific Gold Farms, speculated that by concentrating the pests in one place, an effective trap crop could be managed with bug vacs, thus eliminating the need for growers to run vacuum units across their entire strawberry plantings. If effective, the approach would not only decrease WTPB damage to the strawberry crop, but would save time and energy by cutting down on the area that needed to be vacuumed, and would conserve populations of beneficial insects in the crops. In 2002 and 2003 the Center research team of Swezey and research assistants Janet Bryer and Diego Nieto worked with Eddings and his staff at a Pacific Gold Farms site in Prunedale to test their theory. Grants from the Organic Farming Research Foundation and the US Department of Agriculture’s Western Sustainable Agriculture Research and Education program supported the work.Using a hand-held suction device, Bryer and Nieto collected insect samples in the trap crop plantings weekly beginning in January 2003.

The samples were then frozen and insects were identified and counted under a dissecting microscope. They also monitored insects in row 1 of the strawberry plantings using the same technique. The radish trap crop flowered from February through the end of May, when it was removed. The alfalfa trap crop began flowering in mid April and continued to flower through September. On April 11,strawberry gutter system collaborators from Pacific Gold Farm began vacuuming the beds and trap crops with a tractor-mounted unit that includes three rectangular vacuum collectors that generate a suction of approximately 28 miles/hour . Operators drove the tractor at 1.2 miles per hour when vacuuming the rows, passing over the strawberry canopy at canopy height once a week, and over the alfalfa trap crop row two days a week each week through the season . In mid April, in addition to monitoring the trap crops, Bryer and Nieto began monitoring insects in strawberry rows 1, 2, 4, 8, and 16. They also examined berries from four randomly selected clusters of four strawberry plants ; each week, developing berries that showed signs of distinct WTPB damage were counted and removed, while undamaged berries were counted once they matured. Adult WTPB were first found in the radish trap crop vegetation on January 7, and in the alfalfa trap crop in mid April, when it began to flower. Based on a heat unit accumulation model1 initiated when the first adult was found on January 7, the researchers predicted that a second-generation adult would not mature until July 19 at the earliest; therefore, the WTPB adults found any time before this date had migrated to the crop . This result suggests that there is a six-month period during which migrant WTPB adults are attracted to trap crop vegetation at the edge of strawberry fields.

Figure 1 shows total accumulation of WTPB in the unvacuumed trap crop treatments and the adjacent row of strawberries. Significantly more WTPB were found in the alfalfa than in either the radish trap crop or row 1 of strawberries. For seven weeks in April and May, when both the radish and alfalfa trap crops attracted adult WTPB or nymphs hatched in the vegetation, and when the grower was conducting commercial field vacuuming treatments, alfalfa attracted or retained over 7 times more WTPB than the radish trap crop. Although it flowers and matures somewhat later in the spring, alfalfa was a significantly more effective trap crop for WTPB. This result has management implications for central coast growers. “We’d experimented with a variety of trap crops through the years, including radish, mustard, alyssum, and other flowering annuals and perennials,” says Swezey. “But we’ve found that the radish and some of the other crops can become difficult to deal with once they begin to die back in the summer. Given the results of this study, which show that alfalfa is far more effective at attracting WTPB, we are focusing on alfalfa.” Because heavy spring rains often continue through April, tractor-mounted vacuum management of a trap crop can only begin in early May, when muddy conditions have diminished. This is an optimum time to begin alfalfa trap crop vacuuming. Pattern of WTPB Numbers and Strawberry Damage by Treatment and Row In June, weekly, tractor-mounted vacuuming of the alfalfa trap crop reduced total WTPB by 70% compared to the unvacuumed trap crop . The vacuumed trap crop treatment had the same accumulated WTPB as either the whole-field vacuuming treatment or the untreated control. In contrast, the unvacuumed trap crop consistently accumulated higher numbers of WTPB in strawberry rows 1, 2, 4, and 8. There were no differences among treatments at row 16, indicating that the trap crop’s effect on WTPB numbers ended somewhere between rows 8 and 16. Why the total WTPB numbers in the untreated control were consistently low in June is not clear. It’s possible that whole-field vacuuming in the commercial fields surrounding this experiment lowered the general level of WTPB in the small test plots. Movement or “sinking” of WTPB to nearby trap crops could also explain the low numbers in the control plots.

As shown in figure 3 , the vacuumed trap crop treatment had a significantly lower percentage of damaged strawberries than either the whole field vacuuming or the untreated control . Blueberries offer small-scale growers a potentially profitable “niche” crop that can be developed as a U-pick operation or incorporated into other marketing activities. Although the plants need several years to get established and require careful soil preparation and fertility management, a successful blueberry crop can generate $30,000 to $50,000 per acre . To learn more about the best-performing varietal options for organic growers on California’s central coast, the Center initiated a variety trial of mostly low-chill, high bush blueberries at the UCSC Farm in the fall of 2003. This project is being conducted in collaboration with Aziz Baameur, Small Farm Program Advisor for Santa Clara County’s UC Cooperative Extension office, and Mark Bolda, UCCE’s central coast Strawberry and Caneberry Advisor. Blueberries need well-drained, acidic soil in order to thrive. In November 2003, UCSC Farm manager Jim Leap applied sulfur to the trial site at a rate of approximately 2,000 pounds per acre as well as 3–4 inches of acidic mulch, then created raised beds for the plants. With the help of second-year apprentices Aaron Blyth, Carissa Chiniaeff, Allegra Foley, Estrella Phegan, Ratoya Pilgrim, and Matthew Sutton, the research team planted out 17 varieties of blueberries in January 2004. The trial includes 4 replicates of each variety planted on 3-foot plant in-row spacing with 5 feet between rows. Peat was applied in the planting hole to further lower the pH. Varieties being tested are: Biloxi, Bluecrop, Duke, Emerald, Jewel, Jubilee, Misty, Oneal, Ozarkblue, Millennia, Santa Fe, Sapphire, Sharpblue, Southern Belle, Southmoon, Star, and Windsor. After planting, the beds were mulched with several more inches of acidic bark, and drip tape was laid on top of the mulch. Plants are irrigated weekly with the drip tape, and during each irrigation vinegar is injected into the irrigation water to maintain a low pH. Phytamin, a liquid nitrogen fertilizer, is being applied through the drip lines monthly during the summer to maintain adequate nitrogen levels and get the plants off to a strong start. Over the next several years, the research group will evaluate a variety of factors,grow strawberry in containers including overall plant vigor, disease and pest resistance, and eventually, harvest dates, fruit taste and quality, and fruit production. Although the first harvest is still 12 to 18 months away, Leap is excited about the trial. “Blueberries offer a great marketing opportunity for small scale organic growers,” he says, adding that, “this project has also created great opportunities for interactions between the Center and our local UCCE advisors.” A blueberry field day organized by the Center, UCCE, and the Community Alliance with Family Farmers was held in early June, bringing farmers and gardeners to the UCSC Farm for a look at the new plantings. Speakers included Baameur, Leap, and Bolda, as well as UCCE researchers Richard Smith, who discussed organic weed management, and Laura Tourte, who talked about blueberry economics and marketing.As an environmental scientist, Center faculty affiliate Deborah Letourneau believes policy decisions should be based on the best information available at the time. That’s why she’s trying to fill an information gap with her latest research on genetically modified plants.

As insect-resistance is bred into major crops, Letourneau wonders how those crops’ wild relatives might be affected if they pick up the new traits. “There’s been a lot of research on crop-to-crop movement,” said Letourneau, referring to the contamination of organic corn grown adjacent to genetically modified corn. “But we don’t know that much about the biology of wild crop relatives. If genes transferred, would it make them more weedy, more hardy, more invasive?” To address these questions, Letourneau, a professor of environmental studies at UCSC, along with doctoral candidate Joy Hagen and Ingrid Parker, an associate professor of biology, have begun a three-year study to see what the consequences would be if GM genes transferred from Brassica plants through cross-pollination to their wild relatives. Plants in the Brassica, or cole, family include many vegetable crops, such as broccoli, Brussels sprouts, cabbage, cauliflower, and kohlrabi, as well as common weeds like wild radish and wild mustard. “Weed problems translate into economic problems for farmers,” said Letourneau, noting that 75 percent of cole crop production in the United States is concentrated on the Central Coast of California. Stubborn weeds require more herbicide applications, with accompanying higher labor costs and environmental impacts, she said, adding that highly invasive weeds can threaten native species on non-agricultural lands, too. Letourneau is a leading authority on the genetic modi- fication of plants. A member of the National Academy of Sciences’ 12-member panel investigating the environmental consequences of GM plants, she also coedited the 2002 book, Genetically Engineered Organisms: Assessing Environmental and Human Health Effects. Parker’s background is in applying mathematical models to ecological risk assessment for GM crops. More than 25 percent of corn grown in the United States has been genetically engineered to contain the toxin of the Bacillus thuringiensis soil bacterium, which disrupts the digestive system of a caterpillar. Transgenic cotton and potatoes also produce Bt toxin. Little is known about the role Bt-susceptible herbivores, including caterpillars, play in regulating the health and spread of wild crop relatives. In their research project, Letourneau and Hagen are protecting wild relatives from caterpillar damage to see what could happen if modified genes moved from Brassica crops to their wild relatives. The simulation is necessary because the research is being conducted in open fields—not inside greenhouses—where risks of contamination by GM plants would be high, said Letourneau. To mimic an effect of gene transfer, the UCSC researchers are spraying Bt on wild radish and wild mustard growing adjacent to commercial cole crops, and they will use models to evaluate the subsequent fitness, weediness, and invasiveness of the weedy relatives, said Letourneau. “We can’t use real transgenic crops, but we wanted to conduct this work where wild relatives live side-by-side with commercial crops,” said Letourneau. Research sites include the Center’s on-campus Farm and agricultural parcels adjacent to natural ecosystems from Wilder State Park to Elkhorn Slough Reserve. Genetic links between crops and weeds are remarkably common, and cole crops are no exception, noted Parker. “In the past, the evolution of many weeds has been driven by genes coming from crops,” she said. “Now those genes will be specially engineered by humans.” Research on consequences for wild relatives is overdue, said Letourneau, noting that field-testing of GM cole crops for California has been under way since 1999. “This kind of research is important now, during the process of risk assessment, to know whether new modified crops should be deregulated or not,” she said. “There are a lot of Bt crops in the pipeline.

Exact timing of a decomissioning of a dam is not an issue studied in literature

The sediment perching phenomenon, in our view, is similar to the decision making proposed by Arrow et al: one waits until the stock is down to a certain value before replenishing the stock.Literature has focussed on the debate of whether a dam should have “design life” or whether it should be run sustainably by using life cycle management strategy. Intergenerational equity requires that a dam either be run sustainably or the generation that benefit from the dam pay for its decomissioning cost . Palmieri et al discussed about a method to generate such fund in a reservoir in China. In addition to these studies, Keohane et al proposed a SFQ model which they suggested could be used in the context of reservoir management. In their model, stock and flow both must be controlled to promote the quality, which in the context of reservoir management problems requires the control of both sediment flow and sediment stock to maintain the quality of the reservoir and reservoir products.Their result implied that if the dam operator has the choice of both sediment removal and restoration, then the threshold that triggers restoration in the absence of choice regarding sediment removal would be lower than the case in which planner has the option to remove sediment. On the other hand, the feasibility of restoration will reduce the optimal sedimentation removal at each level. The author seem to treat restoration as if the asset being restored is renewable. However, we believe that is clearly not the case in reservoir management. However, the issue is similar to much studied machine replacement problem in finance and economics. The major study in the literature was due to Rust,grow bucket who studied the decision of an administrator making decision on repair or replacement of GMC bus engines.

A dam administrator is in a way similar to Harold Zurcher, the bus administrator: making a decision on repair or decomissioning, but most likely, without the option of replacement. Furthermore, with dam, the concept of sustainably running it is more important, where as with the bus, it is not even considered. This class of technique include the investment in erosion control upstream so that the river doesn’t carry a lot of sediment into the reservoir. This method is mainly focussed in rehabilitation of degraded soil and watershed upstream. Literature in sedimentation management emphasize that such management strategies be carried out with the help of landowners upstream as their noncooperation result in the failure of erosion control programs. Sediment management and erosion control techniques may use methods ranging from basic land use changes to the complicated high fixed cost structural methods such as construction of terraces, diversion channels, grassed waterways, check dams. Nonstructural methods include agronomic measures which rely on the regenerative properties of vegetables. Other methods in use include operational measures such as scheduling construction to minimize the area of exposed soil. Land use changes doesn’t involve fixed cost, and may not result in reduced sedimentation yield immediately downstream. Faulkner and McIntyre reported that there were no change in sediment yield even 20 years after the transition to less erosive land use. There are several basic agricultural engineering techniques in erosion control for a detailed study on it. In the United States, Best Management Practices are recommended for erosion control. From the economic point of view, these methods can be divided into two classes: structural methods are fixed cost method with low annual maintance cost and nonstructural methods have no fixed cost, but have relatively higher annual maintanance cost. They also differ in their effcacy: it is recognized that the nonstructural methods can never lead to zero sedimentation yield downstream. Erosion control is also topography dependent.

In countries like Nepal, which is situated in the tectonically active Himalayas, erosion control in the watershed is not considered technically feasible in several possible reservoir sites. This is the same case in Tarbela, the reservoir about which we study in detail later. Excavation are costly options and most of the time, they are the only options once sediments are firmly deposited in the reservoir. Excavation option often depend on sediment volume, grain size, geometry of deposit, available disposal and reuse options and water level and environmental criterion. Dredging is an operation in which sediment is lifted from the bottom of the surface of a waterbody and is deposited elsewhere. In the United States, 500Mm3 sediment is dredged every year. Dry excavation involves completely emptying the reservoir, desiccating the surface and deposits and using earth moving equipment to remove the silt from the surface. Hydraulic excavation will require dewatering dredge slurry after it has been removed from the water surface, so that it can be removed in conventional hauling equipments to dump elsewhere. In small ponds in the united states, there have been some use of explosives to excavate sediments, but such use is rare among the large ponds. Dredging as a long term strategy for reservoir management is possible only if a good dumping site can be found. Although in many mountainous regions, the river downstream is considered the natural target for dumping dredged materials, such dumping is considered environmentally undesirable. There is a related method called Hydrosuction removal system that uses the hydrostatic head at the dam to provide energy for sediment removal. HSRS is of interest because there has been one major economic study of this method in detail. This method is similar to dredging, but it applies the hydraulic head available at the dam as the energy for dredging and is considered cheaper than dredging.

HSRS consists of a barge that controls the flow in the suction and discharge pipe and can be used to move the suction end of the pipe around. The pipe’s upstream end is located at the sediment level in the reservoir and the downstream end is draped over the dam to discharge sediment to downstream. Because of this, its applicability is limited to shorter reservoir. This method is normally considered energy conserving,and environmentally friendly. Public’s perception of dam as a clean source of energy has undergone some changes recently. In particular, the role of a dam as an emitter of green house gas has been asserted by researchers such as Ruud et al and Duchemin et al . Duchemin et al studied methane and carbon dioxide emission in two hydroelectric reservoirs in northern Quebec for two years and found “above average emission fluxes”. Their result showed the emission flux to be five to eight times less than what Ruud et al found out. Though Duchemin et al found the emission was on a much smaller scale than conventional thermal power plants equivalent amounts of energy, studies done in Brazil’s Balbina reservoir , Irion et al showed that the reservoir produces more greenhouse gas than coal fired equivalent due to the vegetation inundated by the reservoir. Such results have made it diffcult for large reservoirs to qualify for carbon credit in carbon markets, even though the small hydropower with no forest inundation often qualify for it. If large dams are sources of substantial emission, then their actual cost to the society is likely to be uncertain for long,dutch bucket for tomatoes since there is significant uncertainty related to the damage function: damage to the society due to GHG induced increase in temperature. Hence the dam operator may know the cost of decomission at any moment, but the cost in the future is uncertain. This calls for the modification in assumption of Palmieri et al that the salvage value of the dam is fixed and constant. This also provides motivation to learn how sediment removal rate will be changed under such scenario. There are two main reasons why a reservoir is decomissioned: the owners may find it economically infeasible or the regulatory agencies may demand that the reservoir is decomissioned. In the United States, Federal Energy Regulatory Commission stated in its statement that it has the right to decomission a project when considering its relicensing request. When a dam is decommissioned, there are three major issues: what should be done regarding the dam? what should be done regarding the sediment deposited in reservoir? How should environmental restoration be carried out? The dam could be left as it is, partially breached or completely removed.

The sediments could be left as it is if dam is left as it is. The other choices regarding sediment management are to allow natural erosion, construction of a channel through the deposits while leaving off chanel sediment as it is, and removal by mechanical excavation or hydraulic dredging.Some agencies may demand that the dam operator restore early fluvial condition. In such case, the dam operator may incur extra costs, apart from sediment management and infrastructure removal.It is reasonable to assume that the change in the cost related to and are relatively known and deterministic, but the change in the salvage cost related to will be uncertain. Such uncertainties also point to the need to study dams in stochastic settings. As we noted earlier, global warming implies higher erosion. Higher erosion increases the sedimentation arrival rate at the reservoir and this leads to the change in the value of reservoir. Our model shows that increase in the sedimentation rate decreases the value of the reservoir, in particular at the lower storage level. This is because increased sedimentation implies increased cost of removal of sediment.The cost of removing the storage is high at the lower level and therefore, increase in sediment is likely to decrease the value of the reservoir. Moreover, as Figure shows, the increased sediment arrival implies increased sediment removal at all level where sediment removal is optimal. Discount rate features in our model in two important ways. The first is that discount rate has its traditional meaning regarding the patience of the society.For example, it is expected that higher discount rate encourages individuals or society to consume more today. It also enters our model in a different way . If the society faces uncertainty about the future of the reservoir, its decision making , under some assumption about the nature of such risk, is akin to increased discount rate. Figure implies that increased discount rate increases sedimentation removal at the lower level water storage. Impatience in this case doesn’t mean the policymaker will lessen the sedimentation removal. At all levels of water storage, increased impatience also increases the value of reservoir by a small amount. It is possible that uncertainty about the future makes people value the reservoir more. Both of these results imply that increased discount rate will not lead to social planner scrambling to abandon the reservoir by decreasing sedimentation removal. The impact of increase in price is also reflected in the increase of value of the reservoir in the entire domain except at the end points. Figure shows this expected result. Figure shows that the impact of increase in implicit price on sediment removal. Higher price led to the increased sediment removal, as water is now more valuable. The results above were all conditional upon several things: that the cost functions were of a particular form, that the social planner was risk neutral and that the sedimentation arrival rate followed a certain temporal path. The debates underlying large reservoirs are often hard to address particularly because in most of the cases most of these functions are also less understood. In deed, the reservoir management literature is only recently trying to understand various aspects of reservoir managements. For example, there are very few works that explain the role of different factors in contributing erosion in the reservoir.Pacific Southwest Interagency Committeeís watershed inventory method is often used in predicting sediment yield from watershed condition but it is a very speculative method. Similarly, few literature exists that explain the precise nature of cost function for removing sediments from the reservoir. As WCD report made clear, the systematic study of reservoirs have recently begun, and hence there is still a lot of scope for identification of different parts of a reservoirís economic system to make a precise and integrated statement about the system. Sustainability of dam is a topic of interest when talking about the consumption of natural resources.

The distribution of new development in 2050 varies under each story line

Since we can estimate the relative percentages of these unit types across our three scenarios, we could then calculate approximate energy use for the new households in each scenario. We adjusted for assumed trends in household energy use and efficiency within each scenario, using the 1985 to 2005 statewide reduction of approximately 15 percent per household as a baseline for the A2 scenario .Under the A2 story line development is dispersed in and around existing urban areas . The new development footprint is highest at over 14,000 acres. The urbanization pattern reflects an urban sprawl pattern of growth that is typical today and likely to continue into the future unless there are changes to planning policies and a reduction in population growth. Dunnigan, an area of the county where growth is currently being proposed, receives new development under A2. The B1 story line has urbanization that is more attracted to existing urban features. Under B1, growth is less dispersed and more concentrated in and around the urban sphere of influence; new development takes up over six thousand acres . Due to the AB32+ story line’s strict infill planning policy and mask on non‐urban lands, almost all new development occurs within existing city boundaries . No development occurs in West Sacramento,hydroponic nft channel which is within the one‐hundred‐year floodplain and was thus masked from development within this scenario.

The urbanization policy reflected in the UPlan variables and the amount of population growth under each story line creates a unique pattern and footprint of development. AB32+ is by far the most compact, has the smallest urban footprint, and consumes the least amount of crop‐ and irrigated land, as well as non‐irrigated grazed lands. The story lines vary in the amount and type of new land uses . Under the A2 story line, for example, residential low, commercial low, and residential very low categories take up 9,081 , 2,687 , and 1,441 acres , respectively, by 2050. In this story line, residential medium‐density development takes up a larger percentage of newly developed land area, and in the AB32+ story line, most development is either residential medium or residential high density. One of the most striking findings is just how little land is required to house future populations at these higher densities. The B1 and AB32+ scenarios require 44 percent and 7 percent of the urbanized land of the A2 scenario respectively. Even holding population increase constant at B1 levels, these scenarios use 63 percent and 38 percent of the land of the A2 scenario; most or all of it within existing urban areas.A detailed GIS map of cropland in Yolo County for 2008 was overlaid onto UPlan results to show the crop acreage lost to urban growth under each scenario. The acreages of crops lost to development varied greatly among the three story lines, ranging from 10,562 in A2 to 3,363 in B1 to 23 in AB32+ . These results reflect the lower total population growth and stricter urbanization policies in the B1 and AB32+ story lines. Alfalfa, processing tomatoes, and pasture lands had the highest acreage loss under the A2 story line. The same three crops were most affected under the B1 story line but impacts were higher on processing tomatoes than alfalfa. In the A2 story line, the new development footprint resulted in about 3 percent of irrigated crop land being lost in the county, while in the B1 story line 1 percent was lost, and for AB32+, only 0.04 percent was lost.

Floodplains were more likely to support urbanization under the A2 story line compared to B1 . The B1 story line assumed much more discouragement to wetland and floodplain urbanization, both for protection of constructed units, and for environmental benefits. Urbanization on wetlands under frequent inundation was unlikely in either scenario, partly because flooding risk discourages building construction. Vernal pools, a landform that supports many endemic species, were more vulnerable to urbanization under the A2 story line . The wetland area is currently increasing in Yolo County due to creation of freshwater wetlands for flood conveyance for the high flows from several northern California waterways to the Sacramento‐San Joaquin River Delta, and for wildlife habitat . Wetland conversion can indeed be a “Best Management Practice” in some circumstances, and there can be additional ecosystem services provided by specific management of wetlands. But the loss of agricultural land is still a significant concern for the viability of agricultural operations, markets, and related industries in the county. The Williamson Act is a California law that reduces property taxes to owners of farmland and open‐space land in exchange for a ten‐year agreement that the land will not be developed. Under the A2 story line, farmers would be more likely release their holdings in the Williamson Act. The A2 outcome was nearly four times greater losses compared to B1, whereas AB32+ assumed no change in Williamson Act . Not surprisingly, transportation‐related GHG emissions from new development vary greatly across the three story lines . As noted above, this difference is a function of assumptions about reduced driving by residents of infill development compared with development on previously unbuilt lands at the urban fringe, about improved vehicle fuel efficiency under the lower GHG emission scenarios, and about different rates of population growth in the three scenarios.

Under the A2 scenario, transportation emissions related to new development are approximately 789,229 metric tons CO2e annually. The B1 scenario produces similar emissions of 254,243 MT CO2e, compared to 63,244 MT CO2e in the AB 32 scenario. .Residential energy‐related greenhouse gas emissions also show strong differences among the three scenarios, due to the lower energy usage of multifamily units compared with single‐ family homes, as well as other assumptions about different efficiency improvements and electric portfolio composition between the scenarios. Annual electricity‐related emissions from new development built in the 2010 to 2050 time period range from 132,104 MT CO2e in the A2 scenario to 60,548 MT CO2e in the B1 scenario, and just 11,536 MT CO2e in the AB32+ scenario. Holding population constant across the three scenarios diminishes differences only slightly; holding assumptions constant about efficiency improvements and changes to utility portfolio mix still yields substantial differences solely due to the different mix of dwellings between infill‐heavy scenarios and the greater urban sprawl in the A2 scenario. Greenhouse gas emissions from residential gas consumption are slightly higher than for electricity consumption, in part because electricity will become cleaner over time as utilities develop renewable production sources; GHG emissions from gas will remain the same per unit of energy. . Annual gas‐related GHG emissions from new development built in the 2010–2050 time period range from 196,414 MT CO2e in the A2 scenario to 84,384 MT CO2e in the B1 scenario to 15,259 MT CO2e in the AB32+ scenario . Many of these reductions result from different assumptions about improved energy efficiency; if those assumptions are held constant at the A2 level, emissions still decline from 196,414 to 147,673 and 106,813 MT CO2e because of different mixes of dwelling types. Thus, GHG emissions from residential energy use, as from transportation, will be much greater if urban development sprawls onto agricultural land in the countryside. Overall, our three scenarios vary dramatically in their GHG emissions from new urbanization . AB32+ produces much lower GHG emissions from residential development— approximately 8 percent of the emissions in A2, or about 14 percent with population held constant. The B1 scenario also produces substantial GHG savings—about 36 percent and 50 percent of those in A2 under the two different population levels. The strong implication is that preserving agricultural land from development is essential if the county is to stabilize and reduce its GHG emissions. 

The preceding analysis shows that a strong growth management framework for Yolo County, by channeling much or all future development into existing urban areas rather than onto agricultural lands, would have significant value in terms of preserving agricultural land,nft growing system and extraordinary value in terms of reducing the county’s GHG emissions. Agriculture plays a modest role in Yolo County’s GHG emissions; farming occupies approximately 87 percent of the land area, but is estimated to produce only 14 percent of total county‐wide GHG emissions in 1990 . Detailed analysis of all urban GHG emissions in the county are not yet available, yet preliminary estimates suggest that the MT of CO2e per hectare of agricultural lands are >70 times less than cities and towns .The A2 scenario produces a relatively dispersed pattern of growth that consumes more farmland, although it is still a small percentage of the county’s agricultural acreage. This would be likely to occur in a pattern often referred to as “leapfrog development,” in which developers build on separated parcels across the agricultural landscape. Such development would occur primarily between and around the towns of Davis and Woodland. Also, to the extent that urbanization generally makes agriculture more difficult , the A2 scenario could amplify operational or economic hardships due to climate change. Higher‐quality soils are present in the floodplain region near the towns of Davis and Woodland, and support the crops with the highest income per acre . This helps explains why leapfrog development in the A2 scenario resulted in the greatest loss of land classified as either excellent or good soils with the Storie Index. Previous UPlan modeling showed, however, that protecting only prime agricultural land in California’s San Joaquin Valley resulted in greater use of less desirable land, and more urban sprawl than prioritizing compact growth . Beardsley et al. also used UPlan to show that compact growth was the most effective way to preserve biologically valuable land in the Central Valley. Such effects would be somewhat less pronounced in the B1 scenario, although our model shows leapfrog development was still widespread in the same locations, just at lower intensities. The AB32+ scenario prohibits most urbanization of current agricultural land, and so these effects would be essentially nonexistent. In a previous survey, growers with land in the Williamson Act tax relief program were more likely to be concerned about climate change . Individuals who are most committed to agricultural preservation are more likely to recognize the need for options to adapt to climate change, especially to decreased water availability .By fragmenting the landscape in the vernal pools and floodplain, urbanization in the A2 scenario could work against the provision of ecosystem services related to water quality, biodiversity conservation, open space, and its aesthetic and recreational value. By adopting a more “business as usual” story line than B1, the A2 scenario would also be less conducive to investment in new programs to restore wetlands waterways, riparian vegetation, and hedgerows in agricultural landscapes, a strategy that could increase these types of ecosystem services as well as carbon sequestration .Urbanized areas with a large percentage of their land covered by asphalt and other hard surfaces absorb solar radiation and reach ambient temperatures well above the surrounding areas . Road, roof, and parking surfaces within urban areas have been shown to lead to increased speed and volume of storm water runoff and lower groundwater recharge . In a nationwide assessment, the large increase in population and assumption of dispersed development under the A2 scenario results in about 10 percent increase in the surface area of impervious surfaces compared to the B1 story line, and at least one‐third of the nation’s wetlands will be affected by 2050 in both scenarios . Urban planning to date has done relatively little to try to mitigate these effects, and by extension our A2 scenario might continue to produce them, especially since the urban footprint would expand under a “business as usual” story line. However, the story lines of the B1 and AB32+ scenarios might well reduce these effects through extensive tree‐planting in urban areas, reduced amounts of paved surfaces, green roofs, lighter‐colored paving and roofing materials, and other steps. The extent to which urban heat island effects would actually undermine agricultural adaptation in Yolo County, however, is highly uncertain. Towns such as Davis and Woodland are relatively small, and would likely produce much smaller warming effects on surrounding farmland than a larger city like Sacramento. Prevailing winds, particularly on summer evenings, are from the west, and would tend to carry the Sacramento region’s heat toward the Sierra Nevada foothills rather than Yolo County.

Only in Adaptation 3 are substantial marginal benefits observed in total demand over time

The main exception to this general trend is the near term of A2, which showed an unexpected lower frequency of no allocation years . Under the climate only scenarios, where land use is held constant at 2008 crop proportions, future irrigation demand is projected to increase in the District . In the near and medium term, average demand is expected to increase by 80 to 90 thousand acre feet, with no notable differences between the B1 and A2 projections . The increase in demand is expected to continue in the latter part of the century, were the warmer and drier A2 climate sequence ultimately prompts higher irrigation demand than B1 . Relative to the historical period, this is an increase in irrigation demand of approximately 26 to 32 percent due to climate alone. Increased demand and greater impact of the GFDL A2 scenario observed in this study are consistent with previous projections for the Sacramento Valley as a whole . Table 3.5 and Figure 3.5 compare the difference in irrigation demand among the three adaptation scenarios relative to the historic period and climate only scenarios. Under Adaptation 1, demand varies to a small extent above and below the zero lines . This suggests two things. First, it indicates that A2 and B1 cropping patterns predicted by the econometric model, which are based on historic weather and market drivers, have less impact on irrigation demand than climate change alone. For example, increases in demand from climate alone are on the order of tens of thousands of acre feet, while the relative impact of Adaptation 1 is only a few thousand of acre‐feet . Second, since demand in the B1scenario shows a slight increase with Adaptation 1,grow bag for blueberry plants the cropping trend projected by econometric model may be less water efficient than the current cropping pattern.

In short, the econometric model predicts a cropping pattern that is likely to be the most economical or profitable in the short‐term rather than what might be the most water efficient. Differences between the A2 and B1 climate sequences highlight this possibility. Since the econometric model predicted similar cropping patterns for B1 and A2 prior to 2036, irrigation demand was also similar. However beginning in 2036, the acreage of alfalfa expands significantly under the B1 climate . Since alfalfa has high water requirements, its expanded acreage leads to a corresponding increase in total irrigation demand for B1 relative to A2 and the historic period . Adaptation 2 also shows increased demand compared to the historical baseline across all periods and emissions scenarios . However, the model indicates that the increase in demand can be minimized to some extent by shifting to a more diverse and water efficient cropping pattern. That said, the marginal savings towards the end of the century are still less than half of the increase in demand due to climate change alone . Adaptation 3 also shows a near‐term demand slightly greater than the historical period. However, as the diversified cropping pattern and improvements in irrigation technology are gradually implemented, far‐term demand declines to approximately 12 percent less than the historical mean for both the B1 and A2 climate sequences . This illustrates that “game‐changing” water savings—savings of the same order of magnitude of climate‐ induced increases—can occur through a combination of progressive irrigation technology improvement, and cropping patterns which are more water efficient and diversified.Because of an overall increase in irrigation demand, groundwater pumping also tends to increase in the far term under both the B1 and A2 climate . Under A2, the groundwater proportion of the District’s supply rises from a historical mean of around 49 percent in the near term to as high as 61 percent in the far term .

It should be mentioned that this historic estimate includes years prior to the operation of Indian Valley reservoir, thus the present fraction is somewhat lower than 49 percent. Overall, this corresponds to a volume of 118 thousand acre feet above the historical mean . Relative to the climate only scenarios, the marginal benefits of Adaptation 1 and Adaptation 2 are somewhat limited in the near and mid term . In short, by integrating cropping pattern changes and improvements in irrigation technology, groundwater pumping was maintained at levels close to the baseline in the near term and yielded reductions of 30 to 50 TAF in the far term. The survey of growers indicates that these are types of practices that growers foresee as potential adaptation measures in the future . Groundwater pumping, and building more pumps and wells, are adaptation practices that farmers seem likely to adopt in the future, and these are discussed further in Section 5.With the passage of the Global Warming Solutions Act of 2006 ,12 California has shown, in the absence of cohesive federal leadership, that local governments are able to adopt a bottom‐up approach to greenhouse gas mitigation . Specific targets set by AB 32 aim to reduce California’s GHG emissions to 1990 levels by 2020 and a further 80 percent by 2050. Recognizing the key role that land‐ use planning will play in achieving these goals, legislators also passed Senate Bill 375 13 in 2008, which requires regional administrative bodies to develop sustainable land‐use plans that are aligned with AB 32 . Agriculture currently occupies 25.4 percent of California’s total land area and generates approximately 6 percent of the state’s total GHG emissions . By contrast, urban areas in California makeup only 4.9 percent of the land area but are the primary source of the state’s transportation and electricity emissions, estimated at 39 percent and 25 percent, respectively .

Moreover, rapid urbanization in California has contributed to the loss of nearly 3.4 million acres of farmland over the last decade and has increased the emissions associated with urban sprawl . At present, AB 32 does not require agricultural producers to report their emissions or to implement mandatory mitigation measures as it does for California’s industrial sector . The state is, however, encouraging farmers to institute voluntary mitigation strategies through various public and private incentive programs . For example, voluntary mitigation projects within California’s agriculture and forestry sectors may be permitted to sell offset credits in a carbon market that has been proposed in the scoping plan laid out by the California Air Resources Board . While CARB and other state agencies have taken the lead in defining these policies, much of the responsibility for climate change planning and policy implementation has been delegated to local governments. For instance, AB 32 and SB 375 now require local governments to either address greenhouse gas mitigation in the environmental impact report that accompanies any update to their general plan or to carry out a specific “climate action plan” filed separately . Consequently, conducting an inventory of GHG emissions is now among the first steps taken by local governments as they plan for future development. To help local governments improve the quality and consistency of their emissions inventories, CARB has collaborated with several organizations to develop tools to standardize inventory methods. For example, the International Council on Local Environmental Initiatives has developed a software package known as the Clean Air Climate Protection Model to better align local methods with national and international standards . Such inventory tools are suitable for appraising emissions from government or municipal operations,blueberry grow bag but are less useful for “community‐wide” assessments. In particular, the emissions from agriculture are often missing from existing inventory tools geared to local planners due to problems of complexity, data availability, boundary effects, and consistency with methods designed for larger spatial scales . Methods to estimate emissions from agriculture within a local inventory framework would be a valuable asset for those developing mitigation and adaptation strategies in rural communities. In this paper, a local inventory of agricultural GHG emissions in 1990 and 2008 is presented for Yolo County, California. Recent mitigation and adaptation initiatives in Yolo County thus provide the policy context for this analysis .

The main objectives of this inventory of agricultural emissions are to: prioritize voluntary mitigation strategies; examine the benefits and trade‐offs of local policies and on‐ farm practices to reduce agricultural emissions; and discuss how involving agricultural stakeholders in the planning process can strengthen mitigation efforts and lay the groundwork for future adaptation.In this study, an inventory of Yolo County’s agricultural GHG emissions was conducted for both the AB 32 base year and the present period . To address the wide range in data availability and analytical capacity that exists across different national or regional scales, the Intergovernmental Panel on Climate Change advocates a three‐tiered approach for identifying the appropriate inventory methods used for the agriculture sector . This tiered system refers to the complexity and geographic specificity of the inventory method in question; with the Tier 1 methods using a simplified default approach and relatively coarse activity data, while the Tier 3 methods involve more sophisticated models and higher resolution activity data . The Tier 1 methods used here have been adapted for local activity data from three main sources: the CARB Technical Support Document for the 1990–2004 California GHG Emissions Inventory ; 2) the U.S. EPA Emissions Inventory Improvement Program Guidelines ; and 3) the 2006 IPCC Guidelines for National GHG Inventories . Supplementary materials , provide detailed equations, activity data, and emissions factors for each emissions category . While strategies to adapt inventory methods to local data were exchanged with the Yolo County Planning Division during the preparation of their recent climate action plan, the present study is an independent assessment of agricultural GHG emissions.Direct N2O emissions were calculated using a Tier 1 approach that estimated nitrogen inputs from the following sources: synthetic N fertilizers, crop residues, urine deposited in pasture, and animal manure . In Yolo County, 16 crop categories accounted for approximately 90 percent of irrigated cropland. The harvested area of each crop was taken from the county crop reports for 1990 and 2008 . To calculate the total amount of synthetic N applied in Yolo County, the recommended N rate for each crop was multiplied by its cropping area and then summed across all crop categories. For a given inventory year, the recommended N rate for each crop was obtained from archived cost and return studies published by the University of California Cooperative Extension . Nitrogen inputs from crop residues for alfalfa, corn, rice, wheat, and miscellaneous grains were calculated using crop production data taken from the county crop reports . Nitrogen excreted by livestock in the form of urine or manure was calculated for the six main livestock groups assuming year‐round production. Emissions from poultry were not calculated, since no large‐scale poultry operations exist in the county . Dairy cattle numbers for both inventory years were taken from the National Agricultural Statistics Service database , while all other livestock numbers were obtained from the county records . Dairy cattle and swine manure were assumed to be stored temporarily in anaerobic lagoons and then spread on fields. All other livestock categories were assumed to deposit their urine in pastures. Indirect N2O emissions were estimated based on the total amounts of N added as synthetic N fertilizer, urine, and manure; and calculated using standard values for the volatilization and leaching rates, and default emission factors .A Tier 1 approach was developed to calculate fuel consumption from mobile farm equipment. Each crop’s annual harvested area was multiplied by its average diesel fuel use per hectare from archived cost and return studies and then summed across all crop categories to determine the total amount of diesel fuel used each year . The amount of CO2, N2O, and methane emitted was determined by multiplying the total amount of diesel fuel consumed by mobile farm equipment by emission factors for each gas . The Tier 1 estimate of emissions from mobile farm equipment was then compared with results generated by the Yolo County Planning Division who used Tier 3 OFFROAD emissions model . The OFFROAD model estimates end‐use fuel consumption based on detailed information collected on equipment population, activity patterns, and emissions factors . A detailed summary of the OFFROAD model framework and activity data specifications is available from CARB .

All land-use systems showed much higher C mineralization rates in the topsoil than subsoil horizons

Andisols dominated by allophanic materials generally contain low KCl-extractable Al concentrations; however, these values may be underestimated due to “induced hydrolysis” of displaced Al and subsequent adsorption of polymeric Al to allophanic materials . The elevated pH associated with the horticultural soils reduced the exchangeable Al3+ concentrations to non-detectable levels , further reducing the potential for Al3+ toxicity. A notable findings in this study was the increase in soil pH and base saturation following land use changes as revealed by the strongly positive correlation between soil pH and exchangeable cations . The high base saturation under horticultural land uses as compared to < 23% for the pine forest and tea plantation soils is associated with the presence of soluble salts derived from lime, horse manure and Kfertilizer application. These soluble salts derived from the agricultural amendments are beneficial to soil fertility as they can be readily taken up by roots to meet plant nutrient requirements. Conversion of pine forest to intensive horticultural crops resulted in the increase of nitrate content by 4–7 fold . This high concentration of nitrate is explained in part by mineralization of horse manure and urea applications and the presence of positive charge on surfaces of nanocrystalline materials to retain anions. According to Auxtero et al. the positive charge of subsurface allophane-rich horizons allowed Andisols to retain mobile anions such as nitrate, which is beneficial for crops. Further,grow bag gardening the higher pH values of the IH soil may contribute to more favorable conditions for nitrification leading to the lower NH4 + and higher NO3 – concentrations found in the profile.

Similar results were reported following forest timber harvest where soil NO3 – increased up to 8-fold shortly after harvest as compared to pre-harvest conditions . Previous studies measured anion exchange capacity of allophane-rich soils ranging from 0.4 to 12.2 cmolc kg−1 . This range of AEC values corresponds to 56 to 1700 mg NO3-N kg−1 , which appears sufficient to accommodate the KCl-extractable NO3 – concentrations that range up to 35 mg NO3-N kg−1 in the IH profile. Evaluation of N content in Java Island, Indonesia with different soil types and land uses showed higher soil N content in Andisols was associated with the presence of nanocrystalline materials . Retention of NO3 – within the soil profile reduces nitrate leaching and provides a readily available N supply for deeply-rooted crops . Under pine forest vegetation , the soil P retention was consistently high throughout the entire pedon . In contrast, the IH land use receiving application of horse manure for the past7 years showed appreciably lowering P retention in the upper 40 cm. The decrease in P retention and the increase of available P in the upper horizons of the IH profile were related to application of horse manure and inorganic SP36 fertilizer . These P dynamics could be associated with competition between organic functional groups derived from the horse manure and the applied P for sorption to the hydroxyl functional groups of the allophanic materials. Organic matter functional groups may block some reactive functional groups on allophanic materials, which in turn reduce P retention. In addition, the increase in pH from 4.5 in the PF soil to pH 6.1 in the topsoil of the IH soil may contribute to reduced P retention. This is supported by negative correlation coefficient between P retention and soil pH .

Maximum phosphate sorption in Andisols often occurs in the pH range of 3.0–4.5 and decreases with increasing soil pH . Thus, the application of animal manure and lime appears to be an effective nutrient management strategy to enhance P availability in these high P fixing Andisols. Higher extractable S concentrations in the PF soil may be due to a combination of enhanced capture of H2S/H2SO4 emissions by the canopy of the pine forest, low S uptake by the pine forest and/or low soluble PO4 concentrations that could displace sorbed SO4. The depth trend for extractable SO4-S consisted of lower concentrations in the topsoil than the subsoil for pine forest and horticultural land uses. This is related to competition with P and organic matter and with the increase in soil pH for horticultural crops . Previous workers have reported that sulfate and phosphate compete for the same anion-binding sites but P is adsorbed stronger than sulfate due to phosphate ions being able to form very strong inner-sphere complexes . In contrast, sulfate forms weaker inner-sphere and outersphere SO4 sorption complexes on short-range ordered materials, with the former becoming more dominant with decreasing pH and increasing sulfate concentrations . Pigna and Violante reported phosphate sorption 2–5 times greater than sulfate in Andisols and by increasing pH, phosphate sorption slightly decreased, whereas sulfate retention decreased dramatically . In addition organic matter competes more effectively with sulfate than with phosphate for sorption sites , resulting in low S availability in the topsoil horizons with high organic matter in the present study. Micro-nutrient availability is typically greater in more acidic soils due to higher metal solubility. In the present study, however, the micro-nutrient availability was higher in the horticultural soils having a higher pH . In particular, the addition of horse manure appears to provide both a source of micro-nutrients as well as high dissolved and particulate organic matter concentrations to enhance metal solubility by complexation.

Therefore, manure additions appear to provide a strong benefit with respect to micro-nutrient availability for agronomic crops.The Andisols in this study contained much higher C stocks to a depth of 1 m as compared to the global average for tropical Oxisols and Ultisols of 9.7 and 8.3 kg m−2 , respectively . Further comparison to Oxisols and Ultisols from the Brazilian Amazon had C stocks from 8.5 to 10.5 kg m−2 , which were 2–3 time lower than the tropical Andisols in this study. These comparisons indicate that Andisols have substantially higher capacity than other mineral soils to preserve organic matter. These results are consistent with those of Torn et al. who concluded that Andisols contain about twice as much organic C per m2 than Oxisols or any other soil orders, except for Histosols and Gelisols. Oxisols and Ultisols are dominated by low activity clays that provide less active mineral surfaces for physical and chemical stabilization of soil organic C . In contrast, N stocks of our tropical Andisols were similar in magnitude to Oxisols and Ultisols in the Brazilian Amazon that varied from 0.71 to 2.3 kg N m−2 , but mostly from 0.7 to 1.3 kg N m−2 in the upper 100 cm . Therefore, the Andisols of this study appeared to store organic matter with a higher C/N ratio than Amazonian Oxisols and Ultisols. Overall, soil carbon and nitrogen stocks in the upper 1 m of soil profiles increased in agricultural soils compared to the pine forest soil . These data appear to suggest degradation of soil organic C and N in the topsoil following conversion to agriculture but compensation by the elevated C and N in sub-soils. This condition results from pedon redistribution of organic C concentrations from topsoil to subsoil horizons. This redistribution may be attributed to a decrease in surface litter under agricultural land use with deeper incorporation of organic matter by tillage, and/or deeper rooting system of some horticultural plants. Alternatively, the appreciably higher bulk densities of the agricultural soils contributed to higher organic C stocks compared to the pine forest soil suggesting a role for compaction in increasing C stocks on volumetric basis. Finally, it is possible that periodic volcanic ash deposits have resulted in burial of organic-rich horizons,plastic grow bag leading to the high organic matter in subsurface horizons. Importantly, in spite of intensive agricultural production for > 100 years, there was no appreciable loss of organic matter from these soils as has been documented in many soils following conversion of forest vegetation to agricultural purposes. Similarly, Panichini et al. reported that disturbance of Andisols in Chili by forest management did not alter carbon storage. They posited that organic matter was stabilized by amorphous materials and organo-mineral complex formation, and the humid climate protected soils from irreversible drying and potential carbon loss. The ability of Andisols to strongly sequester and preserve organic C under various land-use/land management practices was demonstrated by the increase of organic matter in subsoil horizons of agricultural soils compared to the forest soil. In contrast, the lack of an organic matter build up in the topsoil and IH soil receiving horse manure for the last 7 years relative to the FH soil indicate that the added horse manure is quickly mineralized to provide nutrients to the horticultural crops. In addition, the increased N content from inorganic fertilizer may accelerate mineralization of organic C. On the other hand, the zero tillage in the FH soil contributed to the buildup and preservation of organic matter in the FH soil compared to intensive cultivation in the IH soil.

The strong correlation between organic C and Alp and the lack of a significant correlation between organic C and Sio suggest that Al-organic complexes are more important than allophane in preserving organic matter in these tropical Andisols. Microbial biomass C trends showed a positive relationship with total C and extractable DOC. The most evident change with respect to land use was the large decrease in MBC in the topsoil upon conversion from pine forest to agricultural production . Surprisingly, the lowest MBC values were found in the IH soil which received regular additions of horse manure for the past 7 years. Extractable DOC is considered an important carbon source to the microbial community and often correlates with microbial biomass. Extractable DOC represented 1.2–1.6% of total soil organic C for the PF and TP compared to < 1% for the IH and FH soils. This suggests that changes in vegetation possibly resulted in changes to the chemical nature of the organic matter affecting DOC solubility, which may affect substrate availability for the microbial community. Overall, agricultural practices had a strong impact in reducing microbial biomass C in topsoil horizons as compared to the pine forest. The microbial-labile pool of organic C is revealed by C mineralization rates during the incubation period. The overall CO2 mineralization rates followed PF > TP > IH > FH in both topsoil and subsoilhorizons . This agrees well with the highest DOC concentrations found in the PF soil and indicates more easily decomposable organic C substrates were available in PF soil than agricultural land uses. Interestingly, CO2 emissions shifted to IH > PF > TP > FH after day 70 in the topsoil, indicating depletion of easily decomposable C in the PF and TP soils. The much lower C mineralization rates in the subsoil than topsoil horizons were accounted for in part by the higher amorphous material content in the former . Chevallier et al. measured transformation of organic matter in volcanic soils by CO2 respiration and showed that the decomposition decreased as the soil allophane content increased. The low C mineralization rates for the FH profile is likely due to depletion of the microbial labile C pool as new organic carbon inputs were minimal over the last 7 years due to fallowing of the soil. This suggests that the topsoil contains more labile C substrate than subsoil horizons. According to Kavdir et al. , the fresh litter contained labile and easily decomposed materials, which mainly consisted of O-alkyl C. Inputs of new organic matter will be preferentially incorporated into the topsoil horizons and organic matter in the subsoil horizons is likely more strongly stabilized by physical and chemical mechanisms. The formation of metal–humic complexes was shown by positive linear correlation between dissolved organic C with Al- and Fe- extracted by Na-pyrophosphate . Determinant coefficients for Al and Fe were 0.84 and 0.80, respectively, suggesting that about 80% of dissolved organic C was bonded to the short-range ordered materials. The fraction of soil organic C bonded to Al and Fe varied from 25 to 50% with the magnitude following TP > FH > PF > IH in the topsoil and middle portions of the profiles . In contrast, the organic carbon bonded to metals in the lower pedon followed: IH > TP ∼ PF > FH. Previous studies on mineral control of carbon pool in Andisols in the Réunion Island showed the largest proportion of organic matter occurred as organo-mineral complexes .

The Department of Climate Change and Meteorological releases a forecast for that season

Networks are defined as “nodes of individuals, groups, organizations, and related systems that tie in one or more types of interdependencies” . Interdependencies might include shared values, ideas, and information exchanges that are critical to the success of individual actors as well as the network as a whole. Within a social network exists a knowledge network with, “heterogeneously distributed repositories of knowledge and agents that search for, transmit, and create knowledge” . In the context of Malawi’s extension system, a difference in worldviews, lack of coordination, and diversity of messages have remained challenges in providing effective information to farmers . The disconnect of stakeholders cited by Masangano, Kambewa, Bosscher, and Fatch promotes misconceptions and misinformation to farmers by extension providers and affects the quality of extension services throughout the extension system. Therefore, it was necessary to evaluate the structure of organizations providing extension services, engagement amongst stakeholders operating within the network, and transfer of knowledge within the extension system. In fact, an understanding of contemporary agricultural knowledge networks, “highlights the importance of networks of actors who cooperatively work together to deliver relevant knowledge to the right people at the right time and place” . The ability of extension providers in Malawi to communicate consistent messages to farmers was not only dependent on their access to resources, but also the strength of social ties within the network itself. Using social network analysis allowed these networks, social ties,flower bucket and information transfer to be analyzed. Relationships or ties within the network were be evaluated by understanding the direction of ties and measures of centrality which represent the importance of actors relative to one another.

Several types of centrality measures have been identified by Wasserman and Faust and are essential in evaluating the importance of different actors within the network. The first type of centrality measure is degree centrality and concerns the number of ties directly related to an actor or organization of interest. This measure is also differentiated by the number of ties coming to an actor and the number of ties leaving an actor . The second type of centrality measure is betweenness centrality and refers to the number of times an actor is situated between two other actors. This measure captures which actors hold the network together, where key paths of communication exist, and where network breaks could occur. The third type of centrality measure is closeness centrality and relates to the shortest distance between actors relative to a certain starting point. An actor with low closeness centrality must pass through many intermediaries to reach other actors within the network. Bodin and Prell also describe the importance of evaluating the cohesion of the whole network through a measure of network density. Network density is the proportion of ties that exit throughout the whole network and reveals the level of connectedness or cohesion present in the network. Cohesion within the network describes the extent to which the network is interlinked and united. Thus, this information was important in understanding the stakeholder connections within Malawi’s extension system.The private sector organizations are involved in activities to develop structured markets for farmer’s products, provide inputs for crop production processes such as fertilizers and pesticides, and facilitate farmer trainings focused on specific value chains and commodities. The main clientele for private sector participants includes smallholder farmers and public sector actors whose employers pay private companies to learn about specific topics. One private sector participant explained, “we focus on closing the finance gap affecting most small-scale farmers who are forced to sell their produce at harvest because they need money to re-pay the cost of inputs and prepare for the next season.”

The annual number of farmers reached by private sector actors ranges from 350 for a small farmer training company to 5,000 for a large private input supplier. The organizational structure of the larger company is fairly hierarchical with field staff, subject matter experts, and company heads. The organizational structure of the two smaller companies is similar to a cooperative where each employee holds multiple positions and is also a farmer themselves. Although not directly asked during interviews, five participants mentioned having advanced degrees and the majority of participants hold high-level positions within their organizations as Directors, Managers, Subject Matter Experts, Specialists or Team Leaders.Participants from international NGOs are involved in a wide range of activities focused around improving food security, providing emergency response during disasters, supporting national health and nutrition outcomes, and building capacity of local communities to sustainably grow food and improve rural livelihoods. A common word used by international NGO participants to describe their organization’s activities was “resilience.” One participant noted, “we’re trying to build resilience with these farmers. We identify farmers, and then come up with interventions that will build their resilience.” The main clients for international NGO participants are smallholder farmers who participate in agricultural interventions, public sector actors who receive funding for extension activities, and research institutions who receive support for technological innovations. According to interview participants, the annual number of clients served by international NGOs ranged from 5,0000 – 148,000 depending on the number of projects implemented in Malawi. The organizational structure of all participating international NGOs is fairly similar and includes Extension Staff with specific expertise, Project Managers in Malawi, Program Managers located internationally, and international Program Directors overseeing programs in multiple countries. Participants from farmer organizations are involved in activities including agribusiness and marketing, agricultural development and crop production, and the improvement of farmer livelihoods. As one participant noted, “we try to assist these farmers and make their farming a business.”

Participants also explained how they advocate for farmers on a local and national level through proposed policy changes in the National Assembly . Organizations that support farmers serve between 7,000 – 1,000,000 farmers each year. The largest of the farmer organizations operates with a clearly defined organizational structure that begins with individual farmers. Around 10-15 farmers come together to form a Club, several Clubs form Group Action Committees, Group Action Committees come together to form Farmer Associations, and select farmers from the Associations for the Executive Committees of the Association. A Board of Directors manages each Association and the National Farmer Organization headquarters provides support and management of each of the 54 associations in Malawi . Malawi NGOs engage in activities geared towards customizing and disseminating agricultural messages from the public sector or international NGOs to farmers throughout the country. One participant described their organization as “knowledge brokers,” noting that they did not develop content, but customized and tailored messages to fit the needs of specific farmers. The NGOs explained their ability to reach large numbers of farming households through ICTs such as radio and served between 8,000 – 2,000,000 farmers annually. Participants from the local NGOs noted the multitude of positions they and their colleagues hold within their organizations. One participant commented, “I’m the manager of the organization, but I’m also doubling as the Field Officer,square flower bucket which means I have a big job to do. Sometimes it becomes a big challenge for me to fulfill all my duties at once.”Finally, government representatives engage in a wide variety of activities including supporting extension services in livestock, crop production, environmental affairs, fisheries, and irrigation, disseminating agricultural messages to farmers, and supporting rural livelihoods through capacity-building efforts. Two common phrases mentioned by government participants in their explanation of program activities were “climate advisory services” and “nutrition sensitive agriculture.” These participants noted how their organizations strive to incorporate both cross-cutting themes into the interventions they implement with farmers. The number of farmers served by the governmental organizations ranged from 24,000 in a single section to 4,200,000 at DAES. The country is divided into what we call agriculture development divisions . We have eight ADDs and those areas are divided based on the agro-ecological zone. One ADD covers multiple districts with similar agricultural practices that are done there. Below the ADDs we have twenty-eight districts, but we have actually 31 District Agricultural Development Offices because some districts are large and split in two or three offices. Below the DADOs, we have what we called Extension Planning Areas and we have 204 EPA’s. Below the Extension Planning Areas, we have sections. This is the smallest unit. The sections are where we have the agricultural extension officers on the front lines who interface with farmers. Messages are developed by the MoAIWD and then disseminated to the DAES through the extension system described above. One of the most important research questions posed in this study was, “how is information generated in Malawi’s extension system to address climate change?”

In order to answer this question, I sought to understand which organizations develop content and what is the process for generating and improving messages that are disseminated throughout the extension system to address climate change. A total of 85 organizations from international NGOs, Malawi NGOs, private industries, farmer groups, government agencies, and research institutions were referenced by participants. The number and types of organizations that were referenced by participants during interviews is shown in Table 3. One direction relationships were described by participants with the size of the node indicating the level of betweenness with other organizations in the network and are shown in Figure 6. The hierarchical development of content from a few organizations operating within Malawi’s extension network is also illustrated in Figure 6. Seven out of the top ten content developers referenced by participants are government organizations, one is from the U.S. government, one is an international research institution, and one is a Malawi NGO. It is also evident that the majority of Malawi’s extension providers were not referenced by participants as content developers and therefore do not have any directional arrows present. Measures of centrality for the top ten organizations developing content to address climate change in Malawi’s extension system are seen in Table 4. The two organizations with the highest in-degree scores are DAES and DMCCS . Participants noted that they rely on these organization to develop messages that are then customized before the information is disseminated to farmers. Participants explained that DAES provides technical agricultural messages to extension providers, while DMCCS develops and shares information regarding national and local weather conditions. Several participants noted that agricultural content originates from partnerships and information sharing between DAES and other organization such as DARS, CGIARs, and other MoAIWD departments. A representative from DAES explained, “the technologies that come to us normally come from the research institutions like the CGIARS with leadership from the Department of Agricultural Research in Malawi. Our function is then to take the different technologies generated by research and improve them.” Although DAES has the highest in-degree score, DAES staff noted that the technologies they share throughout the extension system originate from research organizations outside Malawi and research departments within the country. Instead of developing the technologies, the role of DAES is to customize and tailor messages about agricultural technologies to meet the needs of specific audiences and communities. Additionally, although MoAIWD has a high in-degree score of 5, several participants noted that technical messages are typically developed through MoAWID’s technical departments before being presented to top officials within the ministry. Additionally, it should be noted that several participants indicated that they did not know which departments within MoAIWD develop climate adaptation messages for farmers. DMCCS has the second highest in-degree score and was commonly referenced as a content developer by participants. One participant shared the type of information provided by DMCCS commenting: Climate information is provided to farmers at the beginning of each growing season. Participants explained that DMCCS staff analyze seasonal, monthly, weekly, and daily weather forecasts and share that information with farmers and extension providers. Information about weather conditions is either disseminated directly to farmers through mass media like ICTs or by extension providers who deliver messages to a specific locality and offer support to farmers to prepare for the growing conditions of a particular season. Although not as commonly referenced, several participants also mentioned weather content being developed and disseminated by DoDMA. The U.S government funded project, SANE also has a high in-degree score of 4.

Food-aid policies have been introduced to complement farm legislation

It was suggested that heterogeneity is a major cause for the gradual processes of diffusion of new technology in agriculture. Farm size differences were found to be the major explanatory variable for differences in the tendency to adopt “lumpy” technology such as tractors and computers . Other dimensions of heterogeneity among individuals that were found to substantially affect technological choices include education, age, information, and risk preferences. The surveys present evidence that differences in physical features such as weather and land guality and infrastructure were responsible for differences In adoption patterns between regions. I-Ieterogeneity of the farm population is reflected by the partial participation in many government commodity programs. Rausser, Zilbennan, and Just demonstrated that high-quality lands are more likely to be utilized by participants in diversion programs who tend to divert low quality lands. Calvin found that size, financial situation, and productive capacity affect program participation choices. Heterogeneity and variability have to be incorporated into policy modeling for several reasons. First, the use of aggregate relationships, which assumes average behavior to be representative, may lead to very erroneous policy predictors. For example, an analysis of the impact of pollution regulations with a representative farm is likely to conclude that the introduction of a pollution tax is likely to reduce both total output and the pollution output ratio. Hochman and Zilberman showed that, for the case of a polluting industry where more cost-effective, modern producers are also more pollution intensive ,procona valencia a pollution tax tends to reduce total pollution but may increase the pollution/output ratio since it may cause the older, least cost-effective, and polluting producers to stop operations.

They also showed that, with heterogeneity, a tax may attain a regional pollution target at least cost but a standard may attain it with more output and cause smaller increases in price. Second, recognition of heterogeneity is essential for analyzing inter group equity efforts. There have been much concern about the relative inputs of agricultural policies on well-being in terms of different sizes and the distribution of income within agriculture and the structure of agricultural industries . Third, impacts of regulation may vary drastically across regions and must be spelled out for distributional analysis. Table 2, taken from Lichtenberg, Zilberman, and Harper , demonstrates the differences in regional \Velfare effects associated with government regulation using parameters of the cotton industry at the late 1970s. The table presents the relative welfare impacts of regulations that increase producer costs by 1 percent. Cotton producers are divided to four regions , and impacts of policies affecting each of these regions are estimated for all producer groups, consumers, and society as a whole. The analysis recognizes export demand for the product, and impacts of the policies on export revenues are also considered. It shows that the overall effects of a I-percent increase in cost in any of the regions are quite small. However, increases in cost in three of the regions are likely to increase overall U. S. wei fare due to increases in price and export revenues. On the other hand, an increase in California’s cost will reduce overall welfare because of the low supply elasticity of producers in that state. A I-percent increase in cost across the board will have a substantial effect on the overall domestic welfare and reduce consumer welfare. It will reduce the welfare of growers at the Southeast and Delta, with high cost and elastic supply, and increase the welfare of California and Plains producers who have lower cost and inelastic supply. Relatively, the distributional impacts reflecting heterogeneity among producers in this example are much larger than the overall efficiency effects.

Agricultural economists, such as Schultz and Cochrane , have realized that some salient features of the agricultural sector led to an “oversupply” trap-namely, situations where rates of return in the agricultural sector are far below the rest of the economy and the income of the rural sector does not keep up with the economy as a whole. The inelastic nature of the demand to agricultural products, the constant development of new agricultural technologies and product varieties, and the “rigid” nature of agricultural assets and inputs are among the causes of this oversupply problem. In recent years, however, it became quite clear that government policies aimed at addressing the “agricultural oversupply problem” made the situation worse. Government price support and inventory management programs actually contributed to increased production and inventory accumulation. Income-support schemes, such as diversion payment and even some set-aside programs, are likely to be contributors to oversupply and, through the resulting low prices, cause the need for further subsidization of the farm sector. These . policies did not decouple income support levels from the actual production levels. They presented incentives to farmers to overinvest and overproduce. A recent study of Just, Lichtenberg, and Zilberman demonstrates empirically that deficiency payments contributed substantially to extensive introduction of center-pivot irrigation and overexploitation of resources in the Midwest. Rausser, Zilberman, and Just argued that, because of land quality heterogeneity, farmers tend to set aside lower quality lands, and that action serves to increase per-acre yield after diversion. High and secure target prices tend to encourage use of variable inputs above what is suggested by market prices, and that serves as another source of increased supply. Finally, it has been recognized that the use of past performance as a base for payment has made target prices serve as a “de facto” price with respect to long term decisions which have contributed to upward bias in agricultural supply.

Thus, an important requirement from new policy regimes in agriculture is that it will not contribute to the oversupply problem but, rather, will mitigate it. Another major concern, closely related to the “oversupply” problem, is the instability of agricultural production levels and prices. The “oversupply” problem, caused by inherent properties of the agricultural sector and modified by government policies, has resulted in agricultural prices and returns that, on the average, are too low. However, prices and product availability have had substantial fluctuations. and the extensive economic literature on stabilization demonstrated that these fluctuations have been sources of much welfare loss. The instability and randomness of agriculture mentioned above have been major contributors to price instability, but other factors have also been sources of instability. Moreover, the inelastic nature of demands of agricultural products has magnified the fluctuation in prices in response to variations in supply. Government has constantly attempted to reduce the variability of agricultural prices through inventory control policies. These policies have been very costly because they have led to rapid accumulations of grain stocks which are expensive to carry and have also led to inventory reduction expenditures such as those associated with the payment-in-kind program of 1983. Research on the economics of stabilization has indicated some of the pitfalls associated with programs aimed at stabilizing prices. They argued that public inventory control activities, in part, served to replace private storage activities but, in essence, were a form of income transfer to producers. They also argued that public inventory support programs may reduce economic welfare by their tendency to lead to excessive srock accumulation. Moreover,flower bucket it seems that some factors that contributed to the oversupply problem also resulted in the excessive inventory problem-including some of the income-support policies of the past. Thus, a policy reform aimed at addressing the oversupply problem should reduce the tendency to excessively accumulate inventories while containing agricultural prices within a reasonable range. The low pnces and returns for producers in the farm sector, representing excessive productive capacity and requiring increasing government supports, have been major issues of concern and the reasons for government policies. The sustainability and the environmental consequence of agricultural activities have also become subjects of much concern. A major cause for the excessive supply and production in agriculture is the I introduction and intensive use of modern inputs such as chemical fertilizers and pesticides. Many of the inputs used by agriculture are exhaustible resources; they include water stocks and quality, top soils, and vulnerability to pesticides . Continuous depletion of these agricultural resources risks the sustainability of existing production levels-not to mention the ability to increase production in the long run. Moreover, the use of modern inputs in agriculture has resulted in substantial j externality costs.

Agricultural chemicals are major contaminants of bodies of water reducing productivity of many fisheries and risking the health of consumers. For example, the use of DBCP in California has resulted in a substantial cost of providing safe drinking water . While it is difficult to quantify the costs of groundwater contaminations by agriculture, a partial estimation of these costs done by Christensen and Ribaudo showed it to be higher than $2.5 billion annually. Thus, the “flip side” of the “excessive supply” problem is the excessive depletion of agricultural resources and negative externalities imposed by agriculture. Note that a reduction in production levels may alleviate both problems, and policies addressing one problem may also serve to address the other problem. Another issue of concern is maintenance of the competitive structure of agriculture and the traditional life-style viability of rural communities. This concern is of much importance in Europe where countries such as France and Germany have made substantial efforts in preserving their rural communities and life style. Technological changes, combined with the rise in labor cost and reduction in food prices, tend to increase the size of viable agricultural operations and may result in a structural change in the average farm size and a substantial reduction in the number of farms. This process endangers the survival of many “family farms” and preservation of the rural sector as we know it. The government is pressured to step in and to slow down this process and mitigate its impacts. Equity and distributional considerations playa crucial role in policy design. As Pe1tzman argued, the distributional effects of a policy reform plan determine its political palatability: Therefore, policy analysis and design efforts have to estimate the distributional implications of a proposed policy and suggest transfer and compensation arrangements that will assure the policymaker political support. One has to distinguish between intersectoral and intrasectoral considerations and address both in policy analysis. One manifestation of intersectoral heterogeneity is farm size distribution. Regional heterogeneity is another source of concern, and regional considerations are especially important in determining the political response to agricultural policy reform. Furthermore, the intraregional impacts of certain policies may be larger in relative terms than the other efficiency effects. Regional impacts should be assessed in the design of policy reform, and regional considerations should have a high priority in the design of compensation schemes needed to politically facilitate welfare-improving policies. Intrasectoral effects include impacts of policies aimed at one agricultural commodity on economic welfare included with the production and consumption of other products. The first type of impacts includes assessment of, say, sugar import quotas or corn production or impacts of policies affecting the supply and price of corn on the livestock sectors. Agricultural policies have been viewed over the last 30 years as part of a food policy that aimed at providing sufficient and affordable food to the U.S. population. Policy reform should explicitly address impacts of policies on consumers’ welfare, especially welfare of the poor, and introduce mechanisms to address these issues. Finally, a major impetus for the design of agricultural policy reforms is the heavy burden that the finance of agricultural programs imposes on government. Implied government expenditures should be a key criterion for assessment of any new policy design. The changes and problems of the agricultural sector dictate several key objectives that a comprehensive policy may need to meet. These objectives are to secure food supplies at reasonable prices; to prevent hunger and assure adequate nutritional intake for critical population groups ; to assure stable and fair returns and income to farmers and the rural sector; to control depletion of agricultural natural resources and work toward a sustainable agricultural system; to maintain environmental quality and control the negative environmental side effects of agricultural production; to protect the health and safety of farmers, farm workers, and consumers; to preserve the integrity of the rural sector and protect the viability of “family farms” and the competitive nature of agricultural industries; to obtain efficiency in resource allocation and production patterns; to promote innovation and flexibility in agriculture and food production; and to reduce the burden imposed on government financing of agricultural and food programs and policies. Similar objectives were presented by Brandow and Cochrane .

Control plants were watered to soil saturation with nutrient solution every day

To the best of our knowledge, the response of plants with decreased root exodermal suberin levels to water limitation has never been investigated. The importance of plant radial and cellular anatomy has also long been known as critical to our understanding of the role of plant roots in water uptake in the face of water deficit. Therefore, our findings provide direct evidence, via genetic perturbation, for the role of suberin in a specific cell type mediating tomato’s adaptive response to water deficit. Further, they impart a model by which exodermal suberin barriers contribute to whole-plant water relations in the absence of a suberized endodermis. While our findings are informative about the importance of suberin in the maintenance of transpiration and stomatal conductance under soil water deficit, our conclusions are limited to a particular stage of plant growth. Changes in response to water limitation in the field, particularly with genotypes with modified suberin that impart better maintenance of water potential, remains to be investigated. Suberin in plants roots has recently been proposed to be an avenue to combat climate change including via sequestration of atmospheric CO2 as well as conferring drought tolerance. This study provides evidence that root suberin is necessary for tomato’s response to water-deficit conditions. Increasing suberin levels within the root exodermis and/or the endodermis may indeed serve as such an avenue. The constitutive production of exodermal suberin in the drought-tolerant and wild relative of tomato, S. pennellii ,30 litre plant pots bulk certainly provides a clue that maintenance of suberin in non-stressed and stressed conditions may result in such a benefit.

However, trade-offs of such an increase must also be considered. Increased suberin levels have been associated with pathogen tolerance, but can also serve as a barrier to interactions with commensal microorganisms and constrain nutrient uptake, plant growth or seed dormancy. Regardless, this complex process serves as an elegant example of how plant evolution has resulted in a gene regulatory network with the same parts but distinct spatial rewiring and contributions of the different genes. Collectively, this rewiring results in the distinct but precise spatiotemporal biosynthesis and deposition of this specialized polymer to perform the equivalent function of endodermal suberin in a plant’s response to the environment.Seedlings of SlCO2p:TRAP and AtPEPp:TRAP cv. M82 were transplanted into 15 cm × 15 cm × 24 cm pots with Turface Athletic Profile Field & Fairway clay substrate pre-wetted with a nutrient water solution . Plants were grown in a completely randomized design for 31 days in a growth chamber at 22 °C, 70% relative humidity, 16 h/8 h light/dark cycle and 150–200 mmol m−2 s−1 light intensity. For ‘well-watered’ conditions, we maintained substrate moisture at 40–50% soil water content. For water-deficit treatment, we withheld water from the plants for 10 days before harvest, and for waterlogged conditions, we submerged the pot until the root–shoot junction. We harvested the roots as close to relative noon as feasible by immersing the pot into cool water, massaging the root ball free, rinsing three times sequentially with water, dissecting the root tissues and flash-freezing with liquid nitrogen. We harvested the lateral roots and 1 cm root tips of adventitious roots.

Sequencing libraries of adventitious roots were generated for each line in control and waterlogging conditions, and from lateral roots in control, waterlogging and water deficit conditions in four biological replicates per genotype/treatment, except for SlCO2p:TRAP lateral roots in control conditions . Total RNA was isolated from these roots as previously described, and non-strand specific random primer-primed RNA-seq library construction was performed as originally described. RNA-seq libraries were pooled and sequenced with the Illumina HiSeq4000 .Seedlings were transferred to 0.5 l cones containing Turface pre-wetted with a nutrient water solution . All pots were weight adjusted and a small set of pots were dried so that the percentage of water in the soil could be calculated. Plants were then grown in a completely randomized design for 3 weeks in a growth chamber at 22 °C, 70% relative humidity, 16 h/8 h light/dark cycle and ~150 µmol m−2 s−1 light intensity, and watered to soil saturation every other day. At the end of the first week, vermiculite was added to limit water evaporation from the soil. After 3 weeks, plants of each line were randomly assigned into two treatment groups and exposed to different treatments for 10 days. Water-limited plants were exposed to water deficit by adjusting pot weights daily with nutrient solution until a target soil water content of 40–50% was obtained. On the day of harvesting, between 09:00 to 12:00, stomatal conductance and transpiration were measured on the abaxial surface of the terminal leaflet of the third leaf or the youngest fully expanded leaf using a LICOR-6400XT portable photosynthesis system. Light intensity was kept at 1,000 µmol m−2 s−1, with a constant air flow rate of 400 µmol s−1 and a reference CO2 concentration of 400 µmol CO2 mol−1 air. The third primary leaflet was collected for measuring relative water content using a modified version of a previously established protocol. Fresh leaves were cut with a scalpel leaving a 1-cm-long petiole and the total fresh weight was measured. Leaves were then placed in individual zipper-locked plastic bags containing 1 ml of deionized water, making sure that only the leaf petiole is immersed in the solution.

Bags were incubated at 4 °C. After 8 h, leaves were taken out of the bags, placed between two paper towels to absorb excess water and then weighed to determine the turgid weight . Each sample was then placed into a paper bag and dried in a 60 °C dry oven for 3–4 days. Dried samples were weighed , and relative water content was calculated as: RWC  =  × 100/. A section of the fourth leaf, containing the terminal and primary leaflets, was used to measure stem water potential using a pump-up pressure chamber . The root systems were harvested by immersing the cone into water, massaging the root ball free, rinsing and removing excess water with paper towels. The middle section of the root system was sectioned using a scalpel. Around 300 mg of the dissected root tissue were added to Ankon filter bags . Bags were transferred into a glass beaker,wholesale plant containers an excess of chloroform:methanol was added and extracted for 2 h. Fresh chloroform:methanol was replaced and the extraction was repeated overnight under gentle agitation . Fresh chloroform:methanol was added and samples further extracted for 2 h. The extraction was repeated overnight twice with fresh chloroform:methanol . Finally, samples were extracted with methanol for 2 h. Methanol was removed and bags were dried in a vacuum desiccator for 72 h. Suberin monomer analysis was performed in these samples as described below.Co-expression network modules were generated with the WGCNA . Libraries were quantile normalized and a soft threshold of 8 was used to create a scale-free network. A signed network was created choosing a soft thresholding power of 8, minModuleSize of 30, module detection sensitivity deepSplit of 2 and mergeCutHeight of 0.3. Genes with a consensus eigengene connectivity to their module eigengene of lower than 0.2 were removed from the module . Modules were correlated with upregulated genes in DCRi lines described previously.Seven days after sowing, 50–100 primary roots per sample of length ~3 cm from the root tip were cut and placed in a 35-mm-diameter dish containing a 70 µm cell strainer and 4.5 ml enzyme solution , 20 mM KCl, 10 mM CaCl2, 0.1% bovine serum albumin and 0.000194% mercaptoethanol. Cellulase Onozuka R10, Cellulase Onozuka RS and Macerozyme R10 were obtained from Yakoult Pharmaceutical. Pectolyase was obtained from Sigma-Aldrich . After digestion at 25 °C for 2 h at 85 r.p.m. on an orbital shaker with occasional stirring, the cell solution was filtered twice through 40 µm cell strainers and centrifuged for 5 min at 500g in a swinging bucket centrifuge with the acceleration set to minimal. Subsequently, the pellet was resuspended with 1 ml washing solution , 20 mM KCl, 10 mM CaCl2, 0.1% bovine serum albumin and 0.000194% mercaptoethanol and centrifuged for 3 min at 500g. The pellet was resuspended with 1 ml of washing solution and transferred to a 1.7 ml microcentrifuge tube. Samples were centrifuged for 3 min at 500 × g and resuspended to a final concentration of ~1,000 cells per µl. The protoplast suspension was then loaded onto microfluidic chips with v3 chemistry to capture 10,000 cells per sample.

Cells were barcoded with a Chromium Controller . Messenger RNA was reverse transcribed and Illumina libraries were constructed for sequencing with reagents from a 3’ Gene Expression v3 kit according to manufacturer instructions. Sequencing was performed with a NovaSeq 6000 .A trajectory analysis was run for the ground tissue cells after selecting and re-clustering the cell types annotated as exodermis and meristematic zone . Gene expression matrices, dimensionality reduction and clustering were imported into the dynverse wrapper from Seurat and a starting cell was decided within the meristematic zone cluster. Trajectory inference was run using the minimum spanning tree algorithm. The MST method and UMAP coordinates from Seurat were used as input for mclust. Predictive genes or genes that were differentially expressed along the trajectory, specific branches and milestones were identified and visualized with a heat map using dynfeature within the R package dynverse.For sections, roots were divided in 1-cm segments, embedded in 4% agarose and sliced in 120-µm sections using a vibratome. Sections were then incubated in FY088 for 1 h at room temperature in darkness, rinsed three times with water and counterstained with aniline blue for 1 h in darkness. Confocal laser scanning microscopy was performed on a Zeiss Observer Z1 confocal microscope with the ×20 objective and GFP filter . For whole roots, suberin was observed in 7-day-old S. lycopersicum wild-type or mutant seedlings. Whole roots were incubated in methanol for 3 days, changing the methanol daily. Once cleared, roots were incubated in fluorol yellow 088 for 1 h at room temperature in the dark, rinsed three times with methanol and counter stained with aniline blue for 1 h at room temerature in the dark. Roots were mounted and observed with the EVOS cell imaging system using the GFP filter . Root sections were also stained with basic fuchsin . 1 cm segments from the root tip were embedded in 3% agarose and sectioned at 150–200 µM using a vibratome . The sections were stained in Clearsee with basic fuchsin for 30 min and then washed two times and imaged with a Zeiss LSM700 confocal microscope with the ×20 objective; basic fuchsin: 550–561 nm excitation and 570–650 nm detection. Hairy roots of SlASFT transcriptional fusions were imaged with the same confocal and objective, but with excitation at 488 nm and emission at 493–550 nm for GFP, and excitation at 555 nm and emission at 560–800 nm for red fluorescent protein autofluorescence.An average of 80 mg fresh weight root tissue per biological replicate was washed and immediately placed in a 2:1 solution of chloroform:methanol. Subsequently, root samples were extracted in a Soxhlet extractor for 8 h, first with CHCl3, afterwards with methanol to remove all soluble lipids. The delipidated tissues were dried in a desiccator over silica gel and weighed. Suberin monomers were released using boron trifluoride in methanol at 70 °C overnight. Dotriacontane was added to each sample as an internal standard, saturated NaHCO3 was used to stop the transesterification reaction, and monomers were extracted with CHCl3. The CHCl3 fraction was washed with water and residual water removed using Na2SO4. The CHCl3 fraction was then concentrated down to ~50 µl and derivatized with N ,N-bis-trimethylsilyltrifluoroacetamide and pyridine at 70 °C for 40 min. Compounds were separated using gas chromatography and detected using a flame ionization detector as previously described. Compound identification was accomplished using an identical gas chromatography system paired with a mass spectroscopy selective detector . Compounds were identified by their characteristic fragmentation spectra pattern with reference to an internal library of common suberin monomers and the NIST database.Tomato roots were fixed in 2.5% glutaraldehyde solution in phosphate buffer for 1 h at room temperature and subsequently fixed in a fresh mixture of osmium tetroxide with 1.5% potassium ferrocyanide in PB buffer for 1 h. The samples were then washed twice in distilled water and dehydrated in acetone solution in a concentration gradient . This was followed by infiltration in LR White resin in a concentration gradient and finally polymerized for 48 h at 60 °C in an oven in atmospheric nitrogen. Ultrathin sections were cut transversely at 2, 5 and 8 mm from the root tip, the middle of the root and 1 mm below the hypocotyl–root junction using a Leica Ultracut UC7 , picked up on a copper slot grid 2 × 1 mm and coated with a polystyrene film .

There is no consensus about the best biomarker to assess human exposure to Mn

This study also highlights the importance of traditional management systems and of smallholder agriculture for the conservation of bee communities in transitioning tropical agroecosystems. Manganese is a naturally occurring element found in soil, food, and water. It is mined for use in metal industries, as a gasoline additive, and as an agricultural fungicide. Mn is an essential nutrient but at high doses it is neurotoxic and can result in a syndrome of neurologic deficits called manganism.There is a growing body of evidence that early life exposure to Mn, at much lower doses than those that cause manganism, may have detrimental effects on the developing organism. In school-aged children, lower cognitive scores have been associated with higher levels of Mn in water, in blood and in hair.Pregnancy and the first year of life are potentially vulnerable periods of exposure because Mn crosses the placenta during pregnancy, and young children have increased absorption efficiency and reduced excretion via bile compared to adults.Occupational studies have generally found no association between Mn inhalation exposure and urinary Mn concentrations.Blood Mn has been the most commonly used biomarker of exposure, but the short half-life of Mn in blood may miss periods of peak exposure and Mn is well regulated by homeostatic mechanisms in adults.Higher hair Mn levels have been observed in children living near environmental sources of Mn. However,plants in pots ideas hair is susceptible to exogenous contamination and methods used for cleaning hair samples prior to analysis may affect the accuracy of Mn measurement in hair.Mn levels in nails may be a valid biomarker of cumulative occupational Mn exposure 7–12 months earlier.

In a rodent study, Mn levels in nail clippings were strongly correlated with Mn levels in the brain.Available biomarkers have a limited ability to assess prenatal exposure to the fetus. Even maternal blood Mn levels measured during pregnancy do not accurately reflect exposure to the fetus as cord blood Mn concentrations are consistently much higher than concentrations in maternal delivery blood Mn.Measurement of Mn in deciduous teeth offers a promising biomarker to characterize prenatal and early postnatal Mn exposure. Mn is incorporated directly into developing dentin and current analytical techniques allow for detailed Mn measurements that can be related to specific time periods of neonatal development beginning in the second trimester of pregnancy for incisors and ending 10–11 months after birth for primary coronal dentin in molars.In this study, we analyzed Mn in prenatal dentin of shed teeth from children enrolled in the Center for the Health Assessment of Mothers and Children of Salinas study, a birth cohort of children living in the Salinas Valley. The fungicides maneb and mancozeb contain approximately 21% Mn by weight. Agricultural use of these Mn fungicides averages 160 000 kg per year in the Salinas Valley of California and more than 90% is used on lettuce.Our goal was to determine whether Mn levels in dentin during the entire prenatal period were related to environmental, occupational and dietary sources of Mn exposure. We evaluated the contribution to MnPN from nearby agricultural Mn fungicide use, soil type, estimated concentrations of Mn in ambient air, farm work by the mother or other members of the household, Mn levels in house dust samples, and estimated prenatal Mn intake from maternal diet and tap water consumption. Between September 1999 and November 2000, the CHAMACOS study enrolled 601 pregnant women from health clinics in the Salinas Valley primarily serving low-income families. Participants were eligible if they spoke English or Spanish and qualified for state funding of well-pregnancy care .

A total of 537 liveborns were followed to delivery, of which 353 participated in a visit when the child reached 7-years. We collected 324 teeth from 282 children. We analyzed 237 of these teeth for Mn that were free of obvious defects such as caries and extensive attrition. Analyses for this paper include children who provided a shed incisor with Mn levels measured in prenatal dentin . Written informed consent was obtained from all participants and all research was approved by the University of California, Berkeley Committee for the Protection of Human Subjects prior to commencement of the study. Mothers were interviewed twice during pregnancy and shortly after delivery. Trained bilingual bicultural interviewers obtained information on maternal age, country of birth, education level, and household poverty level. Information was also obtained regarding potential sources of Mn exposure including maternal farm work during pregnancy, number of farm workers in the home, number of farm workers that stored their clothes or shoes indoors and glasses per day of tap water consumed by the mother. We abstracted information on the mother’s hematocrit to hemoglobin ratio from prenatal medical records for a subset of participants to assess maternal iron status during pregnancy. We conducted a home inspection during pregnancy . We collected latitude and longitude coordinates using global positioning system units and evaluated housekeeping characteristics. We also collected house dust samples described in more detail elsewhere.Briefly, we collected dust from one square meter area of the residence using a high volume surface sampler which allows for the calculation of dust loading in grams per square meter of floor area to better characterize Mn in dust available for contact by children.We collected deciduous teeth beginning with the 7-year visit. Participants either mailed or brought in teeth as they were naturally exfoliated. The method for measuring Mn in human teeth has been described in detail elsewhere.Briefly, teeth are sectioned in a vertical plane, and microscopy is used to visualize the neonatal line and incremental markings in sectioned teeth samples. We determined the concentrations and spatial distribution of Mn using laser ablation inductively coupled plasma mass spectroscopy.

Levels of tooth Mn were characterized by normalizing to measured tooth calcium levels to provide a measure independent of variations in tooth mineral density. Values are the area under the curve for points measured during the second trimester and third trimesters separately,container size for blueberries and combined into a prenatal average value . The coefficient of variation for five teeth measured on three different days ranged from 4.5% to 9.5% indicating good reproducibility of 55Mn:43Ca dentin measurements. Of the 207 children with a tooth analyzed for Mn, 131 had dust samples collected from the maternal residence during pregnancy. We stored dust samples at −80 °C for approximately ten years before shipping them on dry ice for analysis. We passed the dust samples through a 150 μm sieve and digested them overnight in 7.5 N nitric acid. We quantified Mn concentrations in dust using inductively coupled plasma optical emission spectroscopy with a limit of detection of 0.1 μg Mn/g dust. We calculated Mn dust loading by multiplying the Mn concentration by the dust loading obtained by weighing the sieved dust sample and dividing by the area sampled. The California Department of Pesticide Regulation maintains the comprehensive California Pesticide Use Report system.Pesticide applicators are legally required to report the active ingredient, quantity applied, acres treated, crop treated, date and location to one square mile in area for all agricultural pesticide applications. We used geographic information system software to geocode residential locations using the latitude and longitude coordinates and to calculate kilograms of maneb and mancozeb reported in the PUR data for combinations of distance from the residence and trimester of pregnancy based on gestational age . We weighted fungicide use near homes based on the proportion of each square-mile Section that was within the buffer around a residence.To account for the potential downwind transport of fungicides from the application site, we obtained data from the five closest meteorological stations in the study area on wind direction to determine the percentage of time during each trimester that the wind blew from each of eight directions. We determined the direction of each section centroid relative to residences and weighted fungicide use in a Section by the percentage of time that the wind blew from that direction for each trimester. Since 90% of agricultural Mn fungicides are used on lettuce in the Salinas Valley, we used Monterey County crop maps for spring, summer, and fall of 199724 to estimate the acres of lettuce within 1, 3, and 5 km of residences during each trimester.

We linked the geocoded residential locations to the appropriate drinking water system using customer service area boundaries provided by local drinking water companies and the state of California.Public drinking water systems provide monitoring data on Mn concentrations sampled at water distribution points.However, Mn was not frequently detected in the study area during the pregnancy period for our cohort. Therefore, we used the average Mn concentration of all available samples from a water system to estimate long-term average concentrations of Mn in tap water. We estimated tap water consumption using questionnaire data on the number of glasses of tap water consumed per day . We multiplied consumption by the average Mn concentration to estimate the average daily Mn intake from tap water during each trimester. Mothers were interviewed about their dietary intake at the time of the second prenatal interview using a modified Spanish-language Block food frequency questionnaire specifically adapted for this study population.For each food item, frequency of consumption and usual portion size were assessed for the previous year. We estimated the mean Mn concentration for each food/beverage item and the daily Mn intake for each women using the average frequency and portion-size of each food and beverage reportedly consumed in a day in combination with food-specific Mn estimates from the total diet study data from 1991 to 2005.We also included Mn intake from dietary supplements. Because iron deficiency might increase Mn uptake, we also estimated daily iron intake using similar methods for use as a covariate in the models.For a subset of participants , we also had hematocrit to hemoglobin ratios as a measure of anemia. We estimated exposure to other potential sources of Mn, including soil type at the residence, estimated Mn concentration in outdoor air, and motor vehicle traffic. To account for variations in soil Mn concentrations, we linked each residence, based on latitude and longitude coordinates, to detailed soil maps.To account for exposure via air inhalation, we assigned residences to a 2000 census tract and linked them to estimated 2002 Mn concentrations in ambient air from U.S. EPA.We also estimated Mn emissions from vehicle traffic at each residence by calculating the traffic density using previously published methods that involve summing vehicle kilometers traveled for all major roads by the length of the road segments within 500 m of the residence.We used ANOVA for bivariate analysis of categorical predictor variables and the Spearman correlation coefficient to evaluate continuous predictor variables We identified potential explanatory variables for inclusion in multi-variable regression models that were associated with MnPN levels with p < 0.2. Mn tooth levels were skewed to the right and we natural log transformed the values to normalize the distributions for regression models. We used manual forward selection to derive final multi-variable linear regression models to determine which Mn exposure sources were significantly associated with Mn levels in dentin during the prenatal period. We also used backward elimination as an alternative method to identify significant predictor variables. We estimated the percentage change associated with each exposure source by exponentiating the regression coefficients, subtracting one and multiplying by 100. We evaluated outliers and reran models excluding one participant with a studentized t-score >3 that also had the lowest measured MnPN level . Our final models included one using data available for all children with MnPN measured in teeth and another for the subset that had both tooth and house dust Mn measurements . We evaluated model fit using residual plots, log likelihood tests and Aikake’s Information Criterion. We investigated nonlinear relationships between continuous predictor variables and tooth Mn levels using penalized splines with 3 degrees of freedom in general additive models. We used Moran’s Global I to assess residual spatial auto correlation of MnPN levels for the final models. We compared Mn levels in prenatal dentin from the second trimester to levels from the third trimester using a paired t test and ran separate regression models by trimester to evaluate significant predictors by trimester.