Nutmeat production. Even though regulated deficit irrigation consistently reduced applied water compared to the control , variation was high enough to prevent the regulated deficit irrigation from having a statistically significant effect on the gallons of irrigation water used to produce 1 pound of nutmeat . Statistical analysis for yield and irrigation water used per pound of nutmeat showed that both block and year effects were highly to very highly significant, presumably as a result of fixed block-to-block variability in the soils as well as the combined effects of year-to-year variation in weather conditions, especially during flowering, and the increasing yields over time. Nut quality. Over 5 years, we found only two statistically significant effects on nut quality under regulated deficit irrigation: a decrease in kernel weight and an increase in the percentage of severe shrivel. Average nut size was 1.18 grams in the regulated deficit irrigation treatment and 1.21 grams in the control . There was severe shrivel in 13.0% of nuts sampled from the regulated deficit irrigation treatment and 9.0% from the control . The non-significant effects measured were nut moisture; percentages of sealed sutures, doubled kernels, twin kernels, blanks, broken kernels, creases, slight shrivels, rupture calluses, gums, molds and stains; and damage by navel orange worm, ants and peach twig borer. For most of the quality factors measured, the effect of year, but not block,plant pot with drainage was also highly to very highly significant . Hull split. Previous research showed that regulated deficit irrigation can increase the rate of hull splitting , but in this study we observed no measurable differences in the duration or extent of hull split between treatments in any year .
Plant water deficit. The SWP values in both treatments were approximately equivalent before and after the regulated deficit irrigation period, but were much lower compared to the control during the hull-split period . This indicates that a well-defined and reproducible plant water deficit was achieved during hull split in the regulated deficit irrigation treatment. For much of the growing season , particularly around harvest time , SWP in the control was also lower than expected for almond trees with non-limited water . This effect may be attributable to a small deficit in water applied by the grower as a result of cutbacks in water availability.The orchard site used in this study presented several difficulties in implementing regulated deficit irrigation as a management technique, in particular the site’s relatively shallow and spatially variable soil with low water-holding capacity, and two comparatively dry years . Both of these factors might lead to an excessive and potentially damaging level of stress when irrigation is reduced, particularly just prior to harvest in almonds, when irrigation must be discontinued to allow for mechanized harvesting. However, using a simple, plant-based approach, consistent water savings of more than 5 inches or about 13% of applied water were achieved with no detectable effects on short- or medium term orchard productivity. When regulated deficit irrigation was compared to the control, there was an annual water savings of 0.4 acre-foot . Although no significant reductions in overall yield or gallons of irrigation water used per pound of nutmeat were observed in our study, significant reductions in yield have been documented in previous deficit experiments with almonds. The negative effects in those studies were not extreme, and the yield reductions were generally associated more strongly with water deficits imposed during post harvest than during hull split. In a 4-year study by Girona et al. , a statistically significant reduction in overall yield was associated with a 40% reduction in water application and a non-significant reduction in kernel dry mass.
In our study, the overall treatment difference in kernel dry mass of 2.5% was statistically significant but relatively minor. At this site, even though the grower annually applied what many consider full ETc, the SWP values indicated that the orchard trees were experiencing mild-to-moderate stress during much of the season, particularly around harvest. According to a previous study, mild to-moderate stress may not be unusual in commercial almond production . Therefore, it is difficult to determine how much water might be saved statewide if our recommendations for regulated deficit irrigation were widely adopted. Our plant-based strategy for regulated deficit irrigation is based on targeted stress levels at specific stages of crop development. If current grower practice already achieves this stress level, then the water savings shown in this study may not be realized. It will be important to further document current practices in terms of both ETc and SWP in order to have a more reliable estimate of the potential water savings from using regulated deficit irrigation in almond orchards. The water savings in our study might also be improved upon. Depending on winter rainfall and soil type, a plant based strategy might allow irrigation to be reduced for longer periods of the season in many almond-producing areas of the state. The contribution from rainfall is another important consideration; during this study there were 2 years of below-average rainfall, and the average annual contribution to crop consumptive water use from soil storage was only 11%. In less droughty years, or on soils with a higher water-holding capacity, water savings from plant-based regulated deficit irrigation might have been greater.Coyote tobacco.Each seed capsule contains more than one hundred seeds and a thrivmg plant may ripen hundreds of capsules. Diminutive seed size confers certain advantages. Tiny seeds incorporate into soil and are insulated from the scorching effects of fire. Tobacco plant foliage may serve as adispersal agent. With a swish of the summer wind, the small seeds spill from the capsules and many adhere to the plant’s sticky stems and leaves.
Dry, wind-blown or hand-tossed tobacco foliage inevitably travels with a cargo of seeds. During high water the small seeds may also raft downstream attached to tobacco fohage and stems associated with flotsam. Although coyote tobacco seeds may germinate the spring after they ripen, the seeds can also wait for optimum conditions, mamtaining their viability for many years—perhaps more than one hundred . Careful investigations reveal that the coyote tobacco seed bank is finely tuned to disturbance, especially by fire. Maximal seed germination is triggered both by an organic compound found in smoke and by the effects of fire, which remove potential competitors and their germination-inhibiting chemicals. Most large stands of coyote tobacco result from range and woodland fires. In the absence of fire, other triggers influence seed germination. Soil disturbance, the removal of plant debris, and competitive vegetation result in a hedge-betting strategy: i.e., the germination of a much smaller portion of the seed bank. Thus, without fire, coyote tobacco sometimes appears along graded roadsides, in washes, sand dunes, stock corrals, and in other disturbance-prone environments where the seeds persist . Coyote tobacco has a vast, mostly inland range that extends from Mexico north to Canada, and from the east slope of the Rocky Mountains to the rain shadowed lower east slopes of the Cascade Mountains of Washington and Oregon. Coyote tobacco is the only native species of tobacco found throughout much of the Great Basin. In CaUfomia its range extends west across the Cascade and the Sierra Nevada mountains to include much of the state TTie scattered populations of coyote tobacco along the Oregon-CaUfomia borderland nearly surroimd the vicinity of the Upper Klamath River and illustrate the wide diversity of environments to which the species is adapted. East of the Upper Klamath River in southeastern Oregon and northeastern CaUfomia,large plastic pots coyote tobacco behaves as it does throughout much of the basin and range country, populating burned rangeland and then disappearing a few years later. In the absence of fire, it appears primarily along graded roadsides, occasionally in dense stands that dwindle within a year or two . Not far to the southeast of the Upper Klamath River, the campground and roadsides of Lava Beds National Monument host a scattered crop of tobacco nearly every year . When a fire swept through the area in 1999, the number of plants increased dramatically and then declined to the occasional scattered individual . A short distance to the northwest of the Upper Klamath River, but well above it, coyote tobacco may be found on Siskiyou Summit, the highest point on Interstate 5. On this pass the vegetation is wind-scoured in winter, but the summer season is generally mild with occasional showers that tend to skirt the drier valleys on both sides. In the summer of 2003, coyote tobacco plants, like a line-up of hitchhikers, occupied both sides of the highway. With access to open habitat, and fertilized with trucker-supplied nitrogenous waste, the plants set tens of thousands of seeds among the roadside foam cups, wads of paper, and plastic bags . To the south and southwest of the study area, coyote tobacco is also found in the Shasta Valley, and in the vicinity of Mt. Shasta . The Klamath River is one of only three rivers that cut entirely through the Cascade-Sierra uplift.
Along the southern Oregon and northern Califomia borderland, the Cascade Range serves as a semi-permeable biogeograpic boundary between two biogeographic regions: the Great Basin Floristic Province and the California Floristic Province .The trough created by the Klamath River as it slices through the Cascade Mountains functions as a corridor connecting portions of the two provinces. The study area includes the landscapes adjacent to and above the Upper Klamath River where the river transitions from the Great Basin Floristic Province to the California Floristic Province. Throughout the Cascade Mountains portion of the Upper Klamath River, the ranges of species characteristic of each region interweave, influencing the kinds and abundance of plants available for cultural use. Since the seed banks of coyote tobacco are seldom manifest as actual plants in the landscape, it is difficult to assess the geographic range of the species on the basis of a single season of observations. For instance, an intensive one-season plant survey of the Irongate Reservoir vicinity in 1996 did not note coyote tobacco, although under the right circumstances the plants are quite common. The Upper Klamath River Project^ allowed participants many opportunities to access vast portions of the landscape for many consecutive growing seasons, enabling us to spot widely dispersed and infrequently occurring stands of wild tobacco. Within the study area, coyote tobacco is a regular summertime resident to the east, on the edge of the dry, Great Basin-like Butte Valley along the OregonCalifornia border. Most August mornings, a sharp eye spots a few small, dusty plants flowering just off the local dirt access roads. The plants respond well to the soil disturbance associated with machine-piled logging slash. One year, robust plants were confined to the vicmity of these piles; the next year, except for a hidden seed bank, they were as absent as the loggers. A dusty ranch with aged outbuildings, adjacent to the Upper Klamath River, is the locale for another small, semi-permanent population. Each year a few plants germinate in the cow- and ATV-churned soil. Single plants and small patches of plants appear and disappear along the rough roads that parallel the river along the Oregon-California border . On one occasion, when a culvert pipe was replaced upslope from Irongate Reservoir, hundreds of plants densely carpeted the area disturbed by the backboe; the next year there were only two plants. The following year there were none, and none have been observed at this location since. While recently burned areas and roadsides are recognized as common habitats for tobacco, riversides are seldom considered to be accommodating to the plants. However, where the Upper Klamath River cuts through the Cascades, coyote tobacco occasionally appears just below the winter-spring high-water line along the banks of the river. After the flood of 1997, a patch of just a few large plants grew up in a silted side channel not far above the 1-5 crossing. Large leaves from these flood-awakened plants were cheerfully harvested by local Shasta tribal member Mary Carpelan . One small gravel bar along the river seems to grow a crop of coyote tobacco year after year. The plants grow best between the river’s high-water mark and its summer low-water edge, holding to the places where occasional floods scour shade-producing riparian shrubs and trees from the bank.