Month: July 2022

Our work takes into account a purposive sample of 23 farmers, and the application of the QM has allowed us to identify prevailing discourses whose interpretation contributes to enriching the debate on PF, providing a new perspective on the subject to policy makers. Additionally, the QM can be used to rethink policies for the dissemination of innovative tools, and, in this regard, provide a better understanding of the transfer of innovation to the agricultural sector to improve the effectiveness of innovation policy. Finally, the discourses of this study can provide new insights to boost responsible policies, even more so since RRI applications to PF are quite limited. The article consists of an introduction, followed by the theoretical background in which the transfer of technology for innovation processes is explored. Then, the key dimensions influencing PFT adoption are discussed, including the sphere of the self. In the third section, the methodology is presented, followed by the results. The discussion and conclusions close the work. In the period of agricultural modernization, innovation has been conceptualised as a linear and unidirectional flow of knowledge of a top down type from researchers to farmers. During the 1960s, the innovation process shifted from a “science push” model to a “market pull” model, underlining the role of demand . These approaches, defined as technology oriented, aim to study the innovation process only through technical and economic factors . Over time, these trajectories, strongly disconnected from the needs of farmers and from the context in which innovation operated, led to explorations of more systemic approaches to innovation, such as the agricultural knowledge and information system and, later, mobile grow rack the agricultural innovation system .

In fact, it was only in the 1990s that innovation was conceptualised as a contextualised “networking process”, implying a learning process between actors. It is precisely this new conceptualisation that marked a change from “topdown” to “bottom-up” approaches, where science and technology are embedded within a social and institutional context . The contextual inclusion of “innovation processes”, well explained by Elzen et al. with the term “anchoring of innovation”, has been highlighted for adoption in the PF field . The literature has shown how anchoring mechanisms are an optimal strategy fostering an environment that is conducive to scaling innovation in this field . On the one hand, this evolution reflects the complexity of anchoring innovation processes in agricultural systems; on the other hand, it reflects that farmers’ thinking has played an increasingly active role in innovation processes over time . Hence, there are numerous contributions that researchers have proposed to try to identify the drivers of and barriers to adoption at the farm level. Even though governments, industry and funding agencies have made efforts to persuade farmers of the benefits of PF, adoption has been low or fragmented. Together with the analysis deepening the complexity of the transfer of innovation, researchers have tried to assess the reasons for this low uptake. First, numerous studies have tried to determine the characteristics of adopters and the contextual factors based on which farmers may more easily accept a new technology in their management . Most studies have pointed out that young farmers appear to be more involved in agricultural innovation . The reasons for this propensity lie in the fact that new generations report a higher level of education and, at the same time, a growing need for information, which is similarly positively correlated with adoption, in addition to greater exposure to and familiarity with virtual technologies .

The need to acquire skills in the use of these tools is also combined with the high investment cost of these tools. In fact, with their ability to absorb costs, large farms have been described as being more willing to adopt innovation. Small enterprises can become PFT adopters through contractors or partnerships . At the same time, the labour intensity indicator gives a clearer idea, in relation to the production activity analysed, of how much agricultural activities are accompanied by new tools or whether manual labour is still present.The role of adopters in the context in which innovation operates has been widely investigated in the literature by identifying numerous dimensions concerning not only the structural dimension and farmer perceptions but also the institutional context . In particular, the institutional context includes social and cultural dynamics and environmental and policy aspects . To understand adopters, researchers have explained how the decision to adopt is only partly linked to the structural and institutional dimensions of farms . Among the factors already mentioned, some studies also include the perceptions of farmers. Perception is the result of a subjective assessment made by the potential user regarding the attributes of innovation and the influences exerted by the structural and institutional dimensions in orienting behaviour in the adoption process . Among the attributes, many authors have focused on the perceived relative advantage and, in particular, farmers’ profitability . Others have highlighted that the perception of the technological and organisational complexity of innovation can significantly influence adoption . Many theories have tried to explain behaviour in the adoption process by emphasising the role of perceptions, the figure of the adopter and background factors .

Since the 1960s, the early theories and models of technology acceptance and adoption have emphasised the role of behaviour and perception as key variables in the adoption process. Fishbein and Ajzen’s theory of planned behaviour  and later extensions postulated that the individual’s behaviour is the result of multiple components, such as attitude, subjective norms, and perceived behavioural control. In social cognitive theory , Bandura reports how behaviour, personal factors , and the external environment of the individual are bidirectionally connected in understanding the adoption process. Davis theorised differently in his technology acceptance model that attitudes are the determinants of behavioural intentions to perform an action or not and are based on perceived ease of use and perceived utility . The TAM itself has been extended by exploring the determinants of perceived utility and perceived ease of use, introducing the relationship between them into the structural dimension . These theories are the starting point and lay the groundwork for investigating the links between i) contextual and structural factors, ii) perceptions, and iii) behaviour that could predispose individuals to adopt new technologies. However, in these models, where perceptions or behaviour is taken into consideration, the agent is always considered rational . This is the vision offered by classical economics, in which the actor manifests autonomous and fixed preferences disconnected from the context . In contrast, in behavioural economics or in the field of sociology, researchers have spoken of “quasi-rational actors” and even “enculturated” decision makers, whose perceptions and behaviours are shaped by the context . The perception-behaviour link has been widely recognised in the psychological research field, which addresses how “perceptions guide action but so too do actions influence what is perceived” . The role of the self in this linkage has been highlighted by Jaswal , affirming that “perception-action coupling is not only manifest in the behavioural arena, but also shows up in the internal processes of the agents, particularly those related to the self”. This is confirmed by Markus and Kitayama , who discuss a mutual and dynamic constitution of context and the self. For example, regarding the concerns of the self, perceptions are subjected to profound social and non-social influences exerting lasting effects on the behaviour and in the moment of decision making due to the context to which individuals have been exposed until that moment .

Reimer et al. is one of the few studies that in the field of adoption that analyses how the characteristics of farmers and farms as well as the and farm context can shape the perception of a new technology and, consequently, the individual’s behavioural intentions towards it. The literature shows the enormous efforts made, especially regarding three aspects: codifying the phases of technology diffusion, theorising adoption models, and identifying the major drivers of and barriers to adoption and all its influencing factors. It is possible to summarise the points previously discussed as follows. The QM that we employed in this work is based on the five-step procedure shown by McKeown and Thomas . The five steps are outlined in Fig. 2. To carry out this analysis, the first two steps are the most important; defining the “concourse” and creating the Q set can affect the whole analysis. The former is the raw material of the Q study that provides the “self-referent notions” arising from shared understanding, whose specific meaning may differ depending on the context . Since the volume of the concourse can be infinite, it has to be dimensionally reduced to obtain the Q set, which is the collection of statements related to the most important aspects of the study theme . The sentences included here should represent a variety of different opinions and feelings rather than being limited to concrete facts . Following the procedure shown by McKeown and Thomas , the concourse was built using scientific publications, newspapers, farmer blogs or interviews, conversations, commentaries, and texts related to the subject. From this review, we defined a final concourse composed of 80 statements . Using an inductive approach , the analysis shows that several dimensions influence farmers’ perceptions of PF and its adoption. These dimensions are not a strict categorisation; rather, they represent a guide to ensure coverage of the most relevant aspects related to farmers’ opinions on PF. Several rounds of discussion were implemented among researchers to delete and rephrase redundant and unclear statements. At the end of the described procedure,ebb and flow table the initial list was refined into a more comprehensive Q sample composed of 33 statements. Q samples must be composed of statements that are “natural” in the language of the participants and “comprehensive” in their representation of the subject to provide individuals with the opportunity to best express their personal opinions . Consequently, the use of academic language should be avoided to facilitate understanding, and a balanced number of positive and negative statements should be included to avoid opposites or similar statements .

Small sheets of paper are used to print the declarations, which are also identified with a code that cannot influence the participant during the process. Before being administered to the sample, the test was tested by a collaborator. In our case, the list of declarations was chosen based on the literature on precision agricultural tool adoption, focusing on drivers and barriers. In the third phase, it is necessary to select participants who are theoretically relevant to the research question and who have a defined perspective to express what matters in relation to the topic . This interview method was first tested among the members of the research group to determine the best way to submit the questionnaire. After a test, it was decided to proceed from the socio-demographic questions and then proceed to the Q sorting phase. The P set is usually smaller than the Q sample, typically from 10 to 40 people . The reason for this can be found in an ancient maxim attributed to Roman Emperor Marcus Aurelius, who stated that “the opinion of 10,000 men has no value if none of them knows anything about the topic”, leading us to the choice of a purposive sample of farmers who have at least “heard of” PF . Therefore, an intentional sample of 23 farmers was selected. The interviews were conducted by two researchers who selected the respondents based on the question “Have you ever heard of innovation, technological innovation, or precision farming in agriculture?” This allowed us to select only those agricultural entrepreneurs who had the necessary conditions to carry out our questionnaire. The interviewees were asked to voluntarily participate in the study. No financial compensation was promised or subsequently awarded. They were informed of the objectives of the investigation, the duration of the interview, and the possibility of abandoning the investigation at any time, and they were given the contact details of the principal investigator for any clarifications or indications on the matter.

The resilience capacities define the possible range of actions to maintain the desired functions of the farming system, i.e. the provision of private and public goods at desirable levels. The selected courses of action in turn also affect the actors, institutions and resources of the farming system and its enabling environment, constituting a feedback loop. Resilience is a latent property of a system. The concept denotes a potential which is activated – and can be observed – only when a system is hit by stress or shocks . It can thus be understood by learning from past trajectories and discussing future scenarios, and from assessing how actual shocks are dealt with . The first approach was used in a systematic assessment of sustainability and resilience over the course of 2017–2020. This provided insight into the multiple factors contributing to resilience. We used the second approachwhen Covid-19 hit European food and agricultural systems. This allowed us to compare the resilience attributes of the system and the resources and institutional support from the enabling environment that were activated to respond to challenges before and during the Covid-19 crisis. The 11 farming systems have been analysed since 2017 in the SURE-Farm project, which has been funded under the EU research program Horizon 2020 and aims to understand and systematically assess the sustainability and resilience of farming systems. Qualitative data on the farming systems during the Covid-19 crisis were collected by members of the SURE-Farm consortium in their respective countries in spring 2020, focussing on exposure to restrictions and sensitivity of the farming system, actions taken by farming system actors in response to restrictions, the role of the enabling environment , stacking pots and discussions and reflections triggered by the crisis .

Due to the short time frame to plan data collection, different methods were used depending on availability and feasibility in each case study. In most case studies, interviews were complemented with a review of media and policy documents . Each case study team interpreted the data with a focus on the anticipating, coping and responsive capacities displayed by the actors in the farming systems, the agility of the actions , the degree of fragmentation or connectedness across actors and the display of leadership, i.e. which actors shaped the interpretation of the situation, and provided guidance and coordination . The findings on the Covid-19 crisis were then compared to previous insights for each farming system, using selected findings from the systematic resilience assessment. These included findings on resilience capacities, the role of the enabling environment, prevailing challenges, and systems’ performance of resilience attributes such as diversity, profitability and openness.Major exposure and sensitivity were observed in the extensive sheep farming system in Northeast Spain and in the small-scale mixed farming system in Northeast Romania, mainly due to severely interrupted sales to restaurants and peasant markets, respectively. In the small-scale mixed system in Northeast Romania also milk collection was interrupted. A medium level of exposure and sensitivity was observed in the fruit & vegetable system in Mazovia. Here the travel limitations for foreign workers created problems. The other farming systems were exposed only to minor degrees. For instance, the dairy system in Flanders faced lower prices, but could continue production and delivery, and in other farming systems the timing of the lockdowns was relatively fortunate, i.e. not affecting harvests but during tillage season or after seeding and planting . In the intensive arable system in Veenkoloni¨en and the extensive cattle grazing system in the Massif Central important markets were barely affected.

Despite only minor exposure and sensitivity in most farming systems, a wide variety of actions was undertaken across all farming systems . Similarities were financial support programs from governments and attempts to set up online-sales channels and home-delivery services. Also, in many farming systems, cooperatives became active. For instance, in the extensive sheep grazing system in Northeast Spain cooperatives kept farm-gate prices at a reasonable level through stimulating national consumption and by developing new markets. In trying to solve shortages of foreign workers, farmers’ associations in the fruit & vegetables system in Mazovia successfully anticipated and started to contact Ukrainian workers directly via Facebook platforms, while the German Farmers’ Association organised flights for migrant workers, among others from Romania and Bulgaria. The Spanish government ensured availability of shearers from Uruguay. In contrast, in the UK the government tried to mobilise local workers, such as through the ‘Pick for Britain’ and ‘Student Land Army’ initiatives, and in the egg & broiler system in South Sweden unavailability of migrant workers was coped with by hiring furloughed labour from companies in the region. Impacts were overall minor . For instance, in the fruit & vegetables system in Mazovia the speed of arranging availability of Ukrainian workers and the switch to less labour-intensive crops reduced the system’s medium exposure and sensitivity to a minor overall impact. The early signalling of the upcoming labour shortage by the farmers’ organisation seemed a pivotal anticipating capacity. Some actions also reduced a system’s exposure and sensitivity. For instance, the agile efforts of Belgian dairy processors to cooperate in order to ensure continuation of milk collection has been an important factor leading to relatively minor consequences in the Flanders dairy system. A somewhat more nuanced view on impacts came from some farming systems which recognised that impacts were unevenly distributed across actors, depending on membership of a cooperative and entrepreneurship . Also, despite minor impacts in the short term, some actors in arable systems expressed concerns about long-term consequences on price levels .

Most of the long list of actions undertaken by farming system actors and the enabling environment suggest coping capacities. This is especially pronounced for the actions undertaken by the enabling environment; only in the hazelnut system in Lazio and the extensive sheep grazing in Northeast Spain the government was partly responsive through changing physical field inspections to georeferencing and by actively engaging in identifying new export markets respectively. We observed more responsive actions at the level of farming systems; in the large-scale arable system in Northeast Bulgaria and in the extensive sheep grazing system in Northeast Spain even the majority of actions by farming system actors were responsive . Anticipation was quite rare and was observed only in the dairy system in Flanders where processors anticipated through crisis protocols, in the arable system in the Altmark where some farmers anticipated and responded by early buying of inputs, and in the fruit & vegetables system in Mazovia in relation to the availability of foreign workers. Although few actions could be classified as responsive behaviour, the discussions and reflections triggered by the crisis dealt with a range of topics which would require fundamental changes in farming systems or food and agricultural sectors in general. Discussions related among others to calls for more self-sufficiency, shorter value chains, reduced dependence on migrant labour, improved fairness and inclusiveness in value chains, more cooperation among farmers, and more innovations . Not much variation in agility could be observed; where needed, actions were taken swiftly . Only in the Hazelnut system in Lazio it was reported that decisions were taken promptly, but that the actual implementation of related actions was slow. Regarding leadership, more differences were observed across farming systems . In the three farming systems with the highest exposure and sensitivity, leadership was taken by actors from the enabling environment in the fruit & vegetables system in Mazovia and in the mixed farming system in Northeast Romania, while in the extensive sheep grazing system in Northeast Spain actors from the farming system itself led important actions. In other farming systems, leadership was jointly taken by actors from the farming system and the enabling environment.

Connectedness was mostly apparent at the level of processing cooperatives or farmers’ associations . Little connectedness was found in the large-scale arable system in Northeast Bulgaria, the extensive beef system in Massif Central, and in the small-scale mixed system in Northeast Romania. In the latter, lack of cooperation along the value chain and between farmers was seen as rooted in the communist history and considered a major problem in developing solutions during the lockdown. In Romania the lack of cooperation was also among the discussion topics . Revealed resilience capacities during the Covid-19 crisis largely coincided with the resilience capacities from the pre-Covid assessment, i.e. also before Covid-19 there was a focus on short-term robustness as indicated by the frequent ‘b’ in Table 4. However, there were a few exceptions. For instance, in the arable system in Northeast Bulgaria and the arable farming system in the East of England the pre-Covid-19 focus of farming systems was on coping capacities while the Covid-19 situation revealed mainly responsive capacities. With regard to actions taken by the enabling environment, the opposite was true in among others the mixed system in Northeast Romania and the egg & broiler system in South Sweden, i.e. there was more focus on supporting coping capacities during Covid-19 than before. A comparison of pre-Covid-19 challenges and those observed during lockdowns shows that a number of challenges persisted during the lockdowns . , observations reported in Table 3 and discussion topics summarised in Appendix B.For instance, each farming system in which labour shortage was already identified as a top- 5 challenge in the pre-Covid-19 assessment also reported labour issues during the lockdowns . Interestingly, in three farming systems respondents reiterated their worries about climate change, i.e. in the arable system in Northeast Bulgaria, the arable system in Veenkoloni¨en, and the fruit & vegetables system in Mazovia, as they feared that exposure, sensitivity and impact of climate change would be much larger than from Covid-19. The Covid-19 crisis also revealed a number of additional challenges . These related to financial distress in the arable system in Northeast Bulgaria and mental stress in the arable system in the Altmark. Actors in three systems also reported problems due to collapse of agritourism activities , while such diversified activities were usually assumed to be less vulnerable to external shocks than agricultural production activities. For the mixed system in Northeast Romania and the sheep grazing system in Northeast Spain also the interrupted sales were an additional challenge. With regard to system characteristics that enhance resilience, grow lights connectedness stood out . Vice versa, lack of connectedness constrained resilience actions. The latter was illustrated by the small-scale mixed system in Northeast Romania in which low connectedness of small farms with value chains hindered small farms to access retail chains when peasant markets closed or were no longer visited by consumers .

System characteristics however did not explain all patterns of Covid-19 resilience actions . In two farming systems we observed that pre-Covid-19 connectedness among farmers was high, but this did not play a role during the Covid-19 crisis. In the hazelnut system in Lazio individual farmers took actions, not the cooperative. Also, in the beef system in Massif Central processors took leadership. The opposite was observed in the fruit & vegetable system in Mazovia where pre-Covid-19 connectedness was low, but the Covid-19 crisis revealed that farmers’ and labour organisations were well able to take joint actions to quickly ensure the availability of Ukrainian workers. In this paper we assessed how and why farming systems in Europe were able to cope with Covid-19. We did so by assessing exposure and sensitivity of farming systems, actions undertaken by farming systemactors and their enabling environment, leadership, connectedness, agility of actions and overall impact. We also assessed discussions triggered by the crisis in media and among stakeholders. Short-term impacts were then compared with pre-Covid-19 knowledge about the farming systems, including systems’ resilience capacities, the role of the enabling environment with regard to resilience, the range of pre-existing challenges and the performance of resilience attributes. In most cases, few anticipatory capacities were observed, even when the impending pandemic became plainly visible through media reports in early 2020. All systems then displayed adequate agility to activate coping capacities. Related actions were led by farming system actors or the enabling environment, or both. Agility was mainly based on already existing connectedness among farmers and more broadly in value chains. Across cases, the experience of the crisis triggered reflexivity about the operation of the farming systems.

According to those findings, there was an elevated nitrogen content in the shoot tissue of the plants, while plant growth was inhibited; in the current study the elevated level likely reflected an increase in stress responses upon exposure to MG. Several plants species have potential for dye decolorization. The decolorization of either the textile effluents or dye mixtures used can be achieved by adsorption and accumulation on plant surfaces, and mostly by phytotransformation or phytodegradationdthe mechanism that degrades or transforms the dye into non-toxic products. The degradation could be enhanced by rhizosphere-associated microorganisms, by enzymes excreted from or within roots  or even by enzyme extracted from leaves  and cell cultures. In the current study, the adsorption of the MG dye to root surfaces, as could be seen by the blue staining, particularly in the treatments with MG of 2 mg/L or 4 mg/L, could be one mechanism that accounts for the depletion of MG dye in the growth solution that occurred in this study. According to Davies et al.,adsorption of xenobiotics followed by its absorption, allows the binding of xenobiotics to plant roots. Retarded roots of B. chinensis growing with MG at 2 mg/ L or 4 mg/L suggests toxicity of MG to plant roots. It has been reported that B. juncea has great potential for Reactive Red 2 degradation which is supported by the activities of the enzyme laccase and NADH-DCIP reductase predominantly present in roots. Nevertheless, Mukherjee and Das  reported that the decolorized level of MG by Enterobacter asburiae Strain XJUHX-4TM decreased as the exposure time and concentration of the dye increased due to the toxicity of the dye to bacterial cells.However,hydroponic nft the 28 d of exposure used in the current study and at higher concentrations  may have caused a reduction in the detoxification ability of the plant and resulted in plant toxicity.

The results obtained from the FTIR analysis can be used as a tool to predict the changes in the functional groups of the original dye molecules. The ATR-FTIR analysis was performed in the study to detect whether or not there were functional groups possibly obtained from MG that had accumulated in the edible plant part. The ATR-FTIR spectra comparison between plant samples from the control and treatment groups suggested that at the concentration of 1 mg/L, MG may be transformed before either being taken up by the plants or translocated into the shoot tissue. Kagalkar et al.  showed that Blumea malcolmii Hook. could degrade MG dye and the degradation gave 4-dimethylaminocyclo-hexa-2,4 dienone as the transformed product. Fu et al.  found that transgenic Arabidopsis converted Crystal Violet to Lleucocrystal Violet,which is non-toxic to the plant, and LCV was then gradually degraded by other endogenous enzyme activities. The products obtained from the phytotransformation of MG were usually non-toxic to tested plant species in all phytotoxicity reports. Hence, this might explain the unaffected growth of B. chinensis in the growth medium with a concentration of 1 mg/L MG, whilst the ATR-FTIR spectra  suggest that there was a similar functional group in MG and in the shoot of plants grown at 2 mg/L MG. Although it might be possible that the functional group originated from MG or could have been obtained from MG degradation, it could also be the substance synthesized by the plant in response to MG. Hence, identification is still needed of the substances, using techniques such as high performance liquid chromatography mass spectrometry. Together with this result, the effects on root growth at MG concentrations of 2 mg/L and above suggested that these concentrations are toxic to root cells and may result in the accumulation of toxic substances in the shoot tissue of B. chinensis. The increased oxalate content in the shoot tissues of plants exposed to MG in the current study might be accounted for by an enhanced tolerance mechanism in the plant, as Nilratnisakorn et al.  suggested that the precipitation of metal-dye complexes in leaves and roots as calcium oxalate, calcium silicate and silica in Typha angustifolia Linn.  is the mechanism that avoids damage to plant cells.

With regard to the potential health risk of some bioaccumulated substances in food products, the accumulation of possibly toxic derivatives obtained from MG transformation such as Leucomalachite Green  in plant tissues still needs to be identified. In addition, as oxalate comprises 75% of kidney stones  and consumption of high oxalate foods can promote the risk of kidney stone formation  in the human urinary tract, B. chinensis grown with MG contaminated water in this study, having increased the oxalate content, may pose a risk of kidney stone formation as well. The results of plant growth revealed that B. chinensis was able to grow in water contaminated with MG at a concentration of 1 mg/L and had the ability to remove the dye from contaminated water through adsorption via its root surface. The tissue contents, total N and total oxalate concentrations, and the ATR-FTIR spectra analyzed in the current study indicated that the tolerance of the plant to low levels of MG could be achieved by increasing stress responses and the accumulation of toxic substances in oxalate form, which hamper toxicity to plant cells. However, the plant could not tolerate high concentrations  of MG resulting in the increased accumulation of toxic substances in plant tissue and the reduction of overall growth as a consequence. A conclusion from the current study is that although the integration of hydroponic plant production for wastewater management in aquaculture that is still using the dye at a low concentration can be applied without noticeable phytotoxicity symptoms, this might pose a potential health risk for humans. Hence, the detection and identification of substances accumulated in plant tissue is still needed.As one interviewee from the Ministry of Agriculture noted “is organic farming sustainable? We think conventional farming is producing sustainable as well and we will support this”. This can be further illustrated by the example of the continued manure problems in the livestock sector, which resulted in a strong exceedance of phosphate emissions in 2018. Based on EU rulings, the Dutch government had to decide reducing the dairy livestock sizes and numerous animals had to be slaughtered. However, organic farmers felt not to be responsible for this problem, while also an expected shortage of organic manure was expected.

In 2018 organic farmers’ associations started a lawsuit against the Dutch government, supported by positive findings of the EU commission on Environment. However, strong resistance came from the conventional Dutch agricultural association which led to the governmental decision not to handle organic livestock differently . As a result, also many organic dairy cows were slaughtered. Regarding the 19 reported barriers, two barriers were identified as high priority , eight barriers a medium priority and seven barriers a low priority . Within the function market formation that accounted for 37% of all barriers, the barrier ‘lack of demand’ was mentioned most often; by 10 of the 13 respondents, and with 77% of high priority. Within the function guidance of the search, one barrier had a high priority , and four had a medium priority. The barrier of the ‘vision on economic growth and export’ was mentioned by 9 of the 13 respondents. Within the function resource mobilization three barriers were identified; two with medium priority and one with low priority. Function F1 accounted for only one medium priority barrier. The functions F2 and F3 had one medium priority barrier and the function F7 one low priority barrier.The observed barriers may lead to systemic problems in the upscaling of organic dairy farming, since they relate both to soft and hard institutional failures . From the first national organic memorandum the Dutch policy vision was to develop the demand side while regular market mechanisms would result in a larger supply and hence an increase of organic dairy farmers. Newspaper articles published at that time were very critical regarding the implementation of the policy. Those articles stated that the Minister of Agriculture relied heavily on market forces and it was questioned whether it could lead to upscaling while price differences between organic and conventional goods remained high. A hard institutional failure can be found in the interplay between the Ministries of Agriculture and Environment . While the Ministry of Environment embraced the sustainability targets of organic farming it did not support this with policy instruments, while within the Ministry of Agriculture the incumbent socio-technological regime blocked specific support to organic farming .

Moreover within the functions ‘market formation’ and ‘entrepreneurial activities’ persistent capacity and capability problems can be identified. First, the lack of consumer demand and lack of stimulation of the consumer were strong barriers. Although earlier organic products could only be purchased through a few specialty shops, this was no longer the case in the second half of the 1990s. Yet from 2010 onwards, newspaper articles also reported a lack of organic supply, and supermarkets had to import organic dairy from other EU countries. Despite this imbalance, some newspaper articles as well as a number of respondents indicated low consumer willingness to purchase organic products due to higher prices. Second, the ‘free-market’ approach also led to a capacity problem of farmers or how Smith states it, a transition problem. This problem was mainly enforced by a hard-institutional failure of lacking transition subsidies, and a soft institutional failure of lacking moral support to farmers during the transition stage. Danish respondents rated the factor ‘goals and initiatives’ an 80% priority as the Danish government has facilitated strongly the development of the sector. By 1986, the Danish Ministry of Agriculture showed an explicit interest in organic farming. This led amongst others to administering of the red Ø-label, hydroponic channel providing subsidies for farmers and a strong support for development and innovation initiatives . Farmers not only received subsidies for the transition phase, but also received environmental subsidies . In 1995 Denmark introduced its first national action plan to promote organic farming. The progress of this action plan was monitored closely and led to a considerable increase in cultivated areas. In 1999 a second action plan was announced with the main goal obtaining a 10% share of cultivated agricultural land . In 2011 ‘The Organic Action Plan 2020’ was introduced. The main goal of this action plan was to double the organically cultivated area by 2020. To realize this plan stakeholder involvement was a necessity. By 2007 this led to a gradual shift from only ‘supply side’ subsidies towards more ‘demand side’ subsidies. More funding was allocated to research, sales promotion, and purchase subsidies for local government canteens, kitchens and hospitals to supply 60% with organic products . Moreover, on the ‘supply side’ also pesticide taxes were introduced that had a direct but moderate effect on the organic sector . Since the implementation, organic farmland has grown by 57% and organic retail sales doubled . Due to these implementations the organic sector went from a small group of self-regulated farmers to a large group of strong legally regulated farmers . Also Austrian respondents rated the factor ‘goals and initiatives’ key in the development of the organic sector . Austria joined the EU in 1995, and faced a low competitive agricultural sector . This was due to the less productive mountainous environment that also resulted in relatively small household farms. The government therefore prepared the sector by “promoting conversion to organic farming as a general strategy for the survival of Austrian agriculture”. Well before the EU accession, farmer organizations, such as the ‘Ernte’ association, developed organic principles independently from the EU regulation . Since its accession and from 2001, Austria continuously implemented organic action programs. These action plans were established to enhance the development of the Austrian organic agriculture sector. Currently the 5th action plan is in place to maintain Austria’s largest share of organic farmland within the EU . In 1987, Denmark introduced conversion subsidies for organic farmers. According to 80% of the respondents, these subsidies enhanced the growth of the organic dairy sector in Denmark. Between 1989 and 1994 the subsidies were mostly aimed at livestock producers .

Recent studies point out that the distribution coefficient of organic pollutants, such as PCBs, on MPs increases with hydrophobicity . In our study, MPs had high levels of dioxins and PCBs while barely detectable levels of pesticides. Dioxins and PCBs have logKow values ranging from 7 to 8 , while pesticides tend to be less hydrophobic. For example, aldrin and dieldrin have logKow values ranging from 5.68 to 7.4, and 4.32 to 6.2, respectively . Thus, hydrophobicity could partly explain the sorption patterns of POPs on MPs observed in this study. PET and PVC MPs placed for 3 months close to salmon farms showed significantly higher levels of POPs than HDPE MPs. Sorption of POPs to MPs depends, in addition to the properties of the POPs mentioned previously, on the properties of the MPs and the water or other matrix surrounding the MPs. Such important properties ar size, crystallinity degree, polarity, colour, occurrence of specific functional groups and surface area of the MPs as well as pH, salinity, temperature of the water and biofilm formation around the MPs . MPs used in this study were non-coloured. PE, PP and PET MPs were similar in size and shape, while uPVC MPs were smaller . Nevertheless, the levels of POPs sorbed to uPVC MPs were similar to the levels found on PET MPs, suggesting that the MP size was not the main factor influencing the amount of POPs sorbed to the different polymers. In addition, PET and PVC in presence of water tend to acquire positive and negative charges, respectively , suggesting that polarity might not play a significant role on the sorption of POPs in this study. The crystallinity of MPs, by contrast, varied among polymers. Crystallinity of polymers is an important factor that affects the sorption of POPs. Crystalline polymers have a well-ordered and firm structure that does not favor sorption of chemicals.

HDPE is characterized by a relatively high crystallinity , while PET and PP are considered semi-crystalline polymers,ebb and flow tray and PVC has amorphous structure. Thus, differences in the sorption of POPs to the four polymers studied may be explained by the degree of crystallinity. However, the level of crystallinity of a polymer can vary considerably as a result of the production process , which could explain differences observed between our study and earlier reports. A study carried out in California, USA, found that HDPE, LDPE and PP MPs deployed for several months in San Diego Bay had significantly higher levels of PCBs and PAHs than PET and PVC MPs . In another study, PE MPs collected in Japanese coastal areas had higher amount of PCBs adsorbed than PP MPs, although the concentrations of PCBs in single pellets from same locations had a high variability . Differences in water temperature, salinity and biofilm formation could also explain the discrepancies with those studies, which were carried out at lower latitudes. Our study was carried out north of the Arctic Polar Circle during the winter, with low seawater temperatures and when the lack of light reduces biofilm growth . To our knowledge there are no previous studies that report sorption patterns of POPs in MPs in waters above the Arctic Polar Circles or in Arctic waters. Thus, comparison with previous studies is not straightforward. Furthermore, studies focused on the mechanisms of sorption of pollutants on MPs have primarily focused on laboratoryscale experiments, which can only heed limited known factors that might influence sorption behaviour. Such cannot sufficiently explain all the mechanisms by which MPs sorb organic pollutants under complex environmental conditions. Several types of pollutants that can exert synergistic or antagonistic effects on one another exist in the natural environment, and the interactions between MPs and pollutants become very complex with the constant changes in environmental conditions.

The above highlights the need to further investigate interactions of chemicals and MPs in diverse regions of the planet to better understand the impact of MPs in the environment. This study focused on the sorption of dioxins and PCBs to MPs and this is, to our knowledge, the first report to show that MPs can bind relatively high levels of dioxins close to salmon farms. The group of POPs evaluated in this work might therefore be a relevant factor for the differences observed between this study and other reports. Previous studies have mainly analysed the sorption of PCBs, brominated flame retardants, pesticides and PAHs on MPs . Very few reports are available on the levels of dioxins bound to MP polymers in the sea. To our knowledge, only one study has reported levels of PCDD/ PCDFs on MPs and such pollutants were only detected in charred MPs collected at the coast of the Maldives . Different types of pollutants can have different affinities to polymers, as shown, inter alia, in our study. For instance, PAHs and chlorinated benzenes were reported to sorb stronger to PE than PP, while PP had higher sorption capacity than PE for hexachlorocyclohexanes . Thus, pollutants with higher affinities to polymers may out compete other pollutants. For example, in a mixture of DDT and phenanthrene, it was observed that the first chemical out competed the latter in terms of MP adsorption . This process could potentially explain the non-correlation observed between the composition of POPs found in the mussels and the MPs. Bio accumulated levels of dioxins in mussels placed next to the MPs for three months in the sea were different to those sorbed to the MPs. Mussels are sentinel species often used to bio-monitor aquatic pollution since they are regarded to generally accumulate pollutants present in the water and have low bio-transformation capacity . Thus, pollutants found in their tissues tend to reflect those found in the surrounding environment.

One possible explanation for the different levels of POPs in MPs and mussels in waters with a cocktail of pollutants could therefore be the competitive binding of pollutants to plastic. In terms of fish farming, this study suggests that PET and PVC MPs could have a higher environmental impact than HDPE MPs. PET and PVC are high-density polymers . Since their densities are higher than seawater , these MP polymers tend to sink and accumulate in benthic sediments , unless they are very small, in the nanoplastic scale, where floatability might vary . Benthic areas beneath fish farms are usually enriched with organic waste, resulting from fish faeces and non-eaten feed pellets, and associated pollutants, which are likely fed on by wild benthic feeding biota. Sediment beneath fish farms could, therefore, be potential sources of polluted MPs to wild organisms. However, the impact of MPs derived pollutants on resident organisms is probably insignificant compared to the exposure to the same pollutants through other pathways , although polluted MPs could represent a environmental threat if carried to non-polluted areas by, for instance, ocean currents. PP MPs also sorbed a significant amount of POPs associated to fish farming. PP has a lower density than seawater and PP MPs will therefore remain for longer periods in the pelagic zone . Thus, PP MPs could have higher capacity to transport POPs from aquaculture facilities to the surrounding areas than other MP polymer types . Furthermore, PP is used in fish farming materials such as mooring ropes, which eventually release MPs as a result of wear and tear . Thus, the impact of this polymer in the environment and in relation to aquaculture could be more important than previously expected. Based on this study, HDPE MPs might play a less important role as vector of POPs from aquaculture facilities to the environment. However, because feeding pipes in salmon farms are a known source of HDPE MPs to the environment , and because the vast majority of materials used in fish farming are made of HDPE, this MP type might still play a significant role in spreading pollutants from fish farms.

Moreover, weathering of plastic and changes in the degree of crystallinity of polymers in the environment could modify the sorption patterns observed in this study . Considering all the above, the role of MPs as potential vectors of pollutants from aquaculture facilities should be studied more in depth and considered in future assessments of the environmental impact of fish farms with open-nets. The role of MPs as vector of such pollutants to organisms or other environments is still a controversial matter . Some studies have shown that pollutants sorbed to MPs can be transferred to organisms under specific conditions. For instance, Murray River rainbow fish exposed to MPs spiked with PBDEs bio-accumulated greater amount of such pollutants compared to individuals exposed to virgin MPs . Other studies have reported that exposure of organisms to pollutants sorbed to MPs is insignificant compared to exposure of pollutants through other pathways, 4×8 flood tray such as diet or environmental exposure . Furthermore, it has been suggested that MPs might reduce bio-availability of such compounds in polluted environments by sorbing pollutants in the water . The aim of this study was to evaluate the potential of MPs to sorb POPs associated with fish farming and, consequently, to act as a possible vector of such pollutants. Our results show that the composition of POPs sorbed to MPs placed for three months next to two fish farms were similar to that of MPs incubated with fish feed for three days, but were significantly different to MPs placed for three months in a harbour and the reference station. This suggests that MPs found in the surroundings of salmon farms can sorb POPs present in the fish feed. However, the ability of MPs to transfer POPs from fish farms to organisms will depend on several factors that were not addressed in this study. Pollution levels in the surrounding environments, ocean current dynamics in the area, species affected or even size and shape of MPs are some important factors to assess when studying the transfer of pollutants from MPs to organisms, which requires further investigation. Therefore, the role of MPs in transfering POPs from salmon farming remains uncertain based solely on our results.

Modern day agriculture in Europe has evolved towards a highly industrial sector by intensification and farm scale enlargements in order to contribute to global food production . The produced commodities compete on world markets resulting in low consumer prices, but also forcing farmers to continuously decrease costs and increase yields through technological innovations and management intensification to maintain their competitiveness . Although food production has considerably increased, it has also led to many adverse impacts on the environment and biodiversity . As a response and triggered by societal pressure, a wide spectrum of sustainable forms of agriculture has been developed over time . These sustainable production systems depend less on external and synthetic inputs and may result in reduced environmental degradation and biodiversity conservation. In many instances, forms of sustainable agriculture start as grassroot movements initiated by social interests . Today, many types exist but are relatively immature to study a long-term sustainability transition . Organic farming emerged in Europe in the early 20th century largely independently by private activities . From 1991 it has been ‘institutionalized’ by the establishment of a European wide organic regulation, the EC Regulation 2092/91 . This replaced most national policies which were established in the 1980s . The regulation of 1991 was repealed, and the current organic legislation falls under council regulation EC NO 834/2007 . For the period from 2014 to 2020 the CAP provided funding for organic farming through the European Agricultural Fund for Rural Development . Each EU country implements their own Rural Development Programme specifically tailored to their own challenges and capabilities . Currently, the European Commission has set out an ambitious action plan for the further development of organic production by member states towards 25% of organic agricultural area by 2030 . Due to the relatively long history, the long term sustainability transition of organic farming can be well studied. Interestingly, despite the more than 30 years of EU legislation and a common internal market, organic farming in EU member states has developed at different rates .

Each fish tank had an associated, 20L bio-filter,made from a plastic storage box. This bio-filter sat above the fish tank and was of a wet/dry trickling design. Water entered the bio-filter by way of a 20 mm airlift pipe,running from the base of the fish tank and into the top of the bio-filter. A 6 mm plastic hose delivered air to the airlift pipe via an air stone. Water from the airlift entered the top of the bio-filter via a “spray bar”, trickled across the biological filter medium  and out through a series of 6 × 10 mm holes  and back into the fish tank. The bio-filter had a plastic “core flute”  lid to lower evaporation. This lid contained a breathing hole in one corner made from a short length of 65 mm PVC pipe to allow gas exchange within the bio-filter. Each tank and bio-filter unit had an associated hydroponic plant growth component which contained standard, washed aquarium gravel  to a depth of approximately 200 mm. This component was rectangular in shape  and was placed above the fish tank/bio-filter unit on a separate shelving system. A submersible water pump  in the fish tank continuously delivered water to the hydroponic component via a 19 mm pipe. Water from the hydroponic component was returned to the fish tank via a 20 mm drainpipe, situated at the opposite end of the hydroponic bed from the water inlet. A continuous flow of water through the hydroponic gravel bed was used because previous experiments  demonstrated that this was the most efficient method for the research-scale aquaponic system for the experimental duration applied. Water for all experimental tanks was supplied from the aquaculture laboratory water supply system. Air for all bio-filters and associated airlifts was supplied by a centralised, pressurised air supply that delivered air to the entire aquaculture lab. Lighting  consisted of six x 400 W metal halide lamps. Lights were situated above the hydroponic beds at a height of 700 mm above the gravel surface, ebb and flow table with one lighting unit located at the interface between two hydroponic subsystems. 

Previous researchers have noted that the nutrient make-up of the water in standard RAS fish systems is sub-optimal for plant growth in recirculating aquaponic systems. This research-scale experiment was designed to determine whether the ionic make-up of the buffer could improve the performance of a recirculating aquaponic system, allowing a controlled pH without negative impacts on fish growth and feed conversion, lettuce growth, yield and health and other test parameters. Fish mortality in all treatments was zero. Ingram  obtained less than 5% mortality for Murray Cod exceeding 50 g in weight in culture trials in tanks. Therefore, the mortality in the present study is what should be expected for Murray Cod of this size  in standard recirculating aquaculture conditions. In terms of feed conversion efficiency, Ingram,using feed containing 43% protein, obtained a mean FCR for Murray Cod over 150 g in weight of 1.2 therefore, the FCR values obtained in the present study  are comparable with research results using industry-standard, recirculating culture methods. Whether the buffer addition regime affects fish growth is also an important question. In the present research-scale study, no significant differences in any fish growth parameter  were detected between any treatments or controls,therefore suggesting that none of the pH buffer treatments tested in this study had a deleterious effect on fish growth or survival. Plant growth, yield and health are the parameters most likely to be significantly affected by the constitution of the buffer added to the recirculating aquaponic system. Whilst the products of fish metabolism supply both nitrogen and phosphorous-based nutrients to the system,the buffer that is added to control the pH drop caused by fish metabolism and bio-filter nitrification is an additional source of the macro-nutrients needed for optimal plant growth. Lettuce production as wet, leaf weight gain or yield  within the four treatments in the present study followed the relationship mixed = potassium > sodium control > calcium,with a significant difference  detected between all treatments, except between the potassium and mixed treatments which exhibited statistically similar results. Therefore, the ionic make-up of the buffer added to the system did affect the efficiency of the aquaponic system in terms of plant production. Yields were equal to or better than those in the studies of Burgoon and Baum,Seawright et al.,Lennard and Leonard,Lennard and Leonard,Geisenhoff et al.,Johnson et al.,Jordan et al.  and Maucieri et al.. 

It is well established in both terrestrial plant production  and standard hydroponic plant production  that beyond nitrogen and phosphorous, potassium and calcium are the next most-important macro-nutrients for plant growth. Potassium plays an essential role in several functions crucial to plants, including the formation of sugars and proteins, carbohydrate synthesis, cell division, water balance and structural rigidity. Calcium also plays an important role, being a major component of cell walls contributing to the support of plant tissues, as well as contributing to enzyme activation and regulation of water movement into and out of cells. All standard hydroponic nutrient solutions contain macro amounts of both potassium and calcium,and it therefore is expected that aquaponic systems need to contain appropriate concentrations or proportions of these two macro-nutrients for efficient plant production. In the present study, whilst mixed  and potassium treatments produced statistically similar lettuce growth and yields, these were statistically significantly higher than those of both the control and calcium treatment systems,with the calcium treatment producing the lowest plant yield. The results of this study therefore, do not fully agree with the findings of other aquaponic studies  that contend that potassium and calcium-based buffers are the most appropriate for recirculating aquaponic systems in terms of plant growth and production, since this study indicates an advantage with a potassium-containing buffer. Net nutrient accumulation within the recirculating aquaponic system is an indicator of balance between fish waste production and plant nutrient use. In the present study, all treatment systems contained statistically similar amounts of nitrate at the end of the experiment ; therefore, no buffer addition was better than any other in terms of nitrate removal by the plants. However, results showed that both potassium and mixed treatments achieved higher plant growth and yield. Therefore, it may be inferred that, whilst the lettuce plants within the potassium and mixed treatments did not remove any more nitrate than did the plants within the calcium and control treatments, they may have used that nitrate more efficiently to achieve more plant tissue growth. Resh,Morgan  and Jensen and Collins  noted that potassium is essential to carbohydrate synthesis in plants.

If potassium levels are too low, carbohydrate and sugar synthesis are blocked, leading to lowered overall plant growth. It seems reasonable therefore, that treatments containing no additional potassium supplementation  may have exhibited lower plant growth and yield than those treatments containing potassium,due to this potential blocking of sugar synthesis. Net accumulation of nitrate within all treatments  and ranged from 7.80 ± 2.20 mg/L  to 13.77 ± 2.23 mg/L. This accumulation is comparable to previous research results using the same aquaponic system with a similar constant flow regime through the gravel plant-growing bed of 11.80 ± 1.78 mg/L over the same time period. Delaide et al.  achieved nitrate accumulations of 58 mg/L in their small-scale, deep-water culture aquaponic system growing lettuce and basil. Hasan et al.  achieved average nitrate accumulations of approximately 40 mg/L after three weeks growing Sangkuriang Catfish  and Nile Tilapia  with Water Spinach  and Lettuce. Dediu et al.  observed nitrate accumulations of 34.52 ± 6.26 mg/L and 32.25 ± 7.06 mg/L in an aquaponic system applying high and low hydraulic retention times growing Bester Sturgeon  and Lettuce. Therefore, nitrate accumulations in the current study compared well with other studies. In terms of final treatment phosphate concentrations, control and potassium treatments were statistically similar,whilst calcium and mixed treatments removed more phosphate than did controls. However, potassium treatments were statistically similar  to both calcium and mixed treatments, and calcium and mixed treatments were statistically similar to each other. From these results it can be inferred that phosphate removal is a complex process. Adler, Harper, Takeda, et al.  argued that when other macro-nutrients are in limiting supplies in hydroponic systems, plants will remove phosphate only to certain levels. The only way to get plants to remove further phosphate from the system is to supply those nutrients that are known to be limited. From the results in the present study, it may be interpreted that some other phosphate removal mechanism may have been involved. Because the control treatment removed statistically no more phosphate than did the potassium treatment, the addition of potassium to the system had little effect on system phosphate removal by plants.

However, it is evident from the results that the addition of calcium to the buffering system had a positive statistical effect on system phosphate removal; systems containing calcium removed more phosphate than did those not contain calcium. This does not necessarily mean that the addition of calcium to the system, via a calcium-based buffer,flood table allowed plants to remove more phosphate. It is known that when excess calcium is added to aquatic systems, it can form a complex with the available phosphate, which then has the ability to precipitate out of the system water, thus lowering available system phosphate levels. This may be the reason why, in the present study, more phosphate was removed from those treatments with calcium supplementation, even though no precipitate was noticed. Net accumulation of phosphate within all treatments  and ranged from 2.60 ± 0.11 mg/L  to 3.92 ± 0.33 mg/L. This is comparable to previous research results using the same aquaponic research system with a similar constant flow regime through the gravel plant-growing bed of 3.87 ± 0.71 mg/L over the same time period. Makhdom et al.  observed phosphate accumulations in an aquaponic system growing Pearl Gourami  and Cherry Tomato  at the highest planting density of approximately 15 mg/L after 30 days. Liang and Chien  achieved phosphate accumulation of 38.1 mg/L  when growing Red Tilapia  and Water Spinach  in an aquaponic system testing feeding frequencies and photoperiods. Therefore, phosphate accumulations in the current study compared well with those of other studies. Dissolved oxygen concentrations  show that the buffer added  had no effect on the ability of the system water to maintain dissolved oxygen concentrations. D.O. was maintained at levels above the minimum requirement for lettuce,warm water, native Australian fishes  and nitrifying bacteria. Previous experiments  demonstrated that the inclusion of plants in the research-scale, recirculating aquaponic system led to an outcome whereby buffer additions to control pH may be lowered  due to the ionic exchange mechanisms that are prevalent when plants are actively assimilating nitrate and phosphate ions. When nitrate and phosphate ions are assimilated by plants, negative ions  are released in order to maintain homeostatic, cellular pH levels within the roots. It is the negative ion portion of the buffer salt added that directly impacts the buffering capacity of the recirculating water.

However, different negative ions have differing capacities to counteract acidification and to buffer pH to desired levels. Because the buffers used in the present study possessed different negative ion constituents,it is difficult to directly compare the amounts of the relative buffers used. However, results  suggest that the amount of buffer required was variable and dependent on the negative ion content of the buffer. There was no significant difference in the amount of buffer required between the two buffers that used bicarbonate as the pH-buffering component. However, significantly less buffer was required in both calcium and mixed treatments. This is because these treatments used the hydroxyl ion as the ion to counteract acidification, and less hydroxyl ion is required to maintain a similar pH in a similar system than bicarbonate ion. This explains why pH levels were more difficult to maintain with the bicarbonate-containing buffers, and why these treatments required significantly higher additions than those treatments using hydroxyl-containing buffers. Therefore, whilst the positive ion component of the buffer used had effects upon plant growth, the relative amounts of the negative ion component of the buffer was the determining factor in pH buffering and maintenance. 

The osmotic potential of the nutrient solutions with and without PEG was calculated according to Bündig et al.  from measured values determined by using an osmometer. For nutrient solutions without PEG, an osmotic potential of -0.013 MPa was calculated, while the solutions with PEG revealed a potential of -0.16 MPa.From 74 to 89 dap, nutrient solutions were changed without the addition of PEG  for both cultivars and K supplies. The plants grew for a total of 89 days in a greenhouse with 12 h light and 12 h darkness at an average temperature of 20.6 ± 7.5 ◦C in a completely randomised design.The phenotype was influenced by K supply, as shown by the example of cultivar Milva in Fig. 3. The +K plants produced more biomass and showed no K deficiency symptoms. Even after the addition of PEG, the plants remained vigorous and only a few chlorosis and necrosis were observed on the oldest leaves. In comparison, the -K plants produced less biomass and both necrosis and chlorosis were observed on the oldest leaves. Under PEG addition, this effect was further enhanced, so that the oldest leaves were almost completely necrotic. Plant height and biomass were significantly affected by K supply with higher rates for +K plants compared to -K plants in both cultivars. The differences between K supplies were higher in Agria starting from the beginning of the measuring period. With PEG addition, plant height and biomass increased for both K supplies compared to plants without PEG addition for ‘Agria’ and ‘Milva’. However, the effect was not significant. In -K plants, water consumption was significantly reduced compared to +K plants in both cultivars ; but, differences between the K levels were again greater in Agria.

The addition of PEG decreased water consumption in Agria at both K levels but increased again after 74 dap. In contrast, water consumption in Milva initially increased due to PEG addition in -K and +K plants,and a delayed decrease in water consumption was observed at 74 dap. However, PEG-induced osmotic stress did not significantly affect water consumption. The number of leaves and internodes was higher in +K plants than in -K plants for both cultivars. Differences were only significant in Agria, flower pot which also produced more leaves compared to Milva.More biomass was produced in +K compared to -K plants of both cultivars, but differences were only significant in Agria. In Milva, +K+PEG and -K+PEG plants produced 13 and 43% more biomass, respectively, than plants of the same K supply without PEG. Side shoots made up the largest proportion of the biomass, followed by leaves. In comparison to the +K-treated plants, the -K plants produced fewer stems, whereas the root biomass developed equally. A similar distribution was observed in Agria, although the +K+PEG plants did not produce more biomass compared to +K plants. The +K plants of Milva accumulated up to three-fold higher  K on the whole plant level compared to -K plants. A higher K content was found in +K plants compared to +K+PEG Milva plants, although the biomass was higher in +K+PEG plants. The highest K content was measured in side shoots and leaves and thus correspond to the biomass and K distribution of individual plant parts. Compared to +K plants, less K was translocated into the leaves and stems of -K plants, reflecting the biomass and K distribution for both cultivars. However, the K content in Agria was almost equal between +K and +K+PEG plants, although the biomass of +K +PEG plants was 20 g lower based on DM. The results for stolons and tubers are shown in Supplementary Table S7.

Reducing sugars accumulated more in -K plants compared to +K plants of both cultivars. However, almost twice the content of reducing sugars was detected in +K and +K+PEG plants of Milva than in Agria. Within plant parts, reducing sugars were accumulated mostly in side shoots and leaves at both K levels and in both cultivars. PEGinduced osmotic stress did not affect the accumulation of reducing sugars in -K and +K plants. In contrast to reducing sugars, the sucrose content was not affected by K treatments. However, the sucrose content was two to three-fold lower than the reducing sugar content and was highest in side shoots and leaves. In Milva more sucrose was measured in +PEG treated plants at both K supplies, while the opposite was observed in Agria. The results for stolons and tubers are shown in Supplementary Table S8.For adaptations to changing environmental conditions, it is important to understand the morphophysiological and metabolic processes of plants to provide specific stress-mitigation strategies. In this study,osmotic stress was induced by adding PEG—with an osmotic pressure in the nutrient solution of -0.16 MPa—to simulate drought stress under hydroponic conditions. Two different K rates were applied to investigate the effect of K on plants tolerance to osmotic stress. Phenotypic observations revealed more biomass and almost no osmotic stress symptoms due to +K fertilisation. In comparison -K plants showed typical chloroses and necrosis on older leaves, which were even more severe with PEG addition. PEG symptoms on older leaves were also described by Büssis et al.,which might be related to a water deficit. Furthermore, the results of this study showed that K supply has a wide range of effects on plant physiological parameters. Weekly determined plant height and biomass decreased under -K conditions compared to +K for both cultivars. This is in accordance with a study on potatoes  and other plant species, including tomato  and wheat. 

A reduction in plant growth is known to be a physiological adaption to insufficient K supply for maintaining the tissue K concentration sufficient for several cell functions. During PEG-induced osmotic stress, plants were still able to grow under both K treatments, which was also observed by Büssis et al.. However, in contrast to their study where PEG-treated plants were inhibited in growth, in our experiment, +PEG plants showed higher growth rates within the osmotic stress period. An increase in growth due to the influence of PEG has been rarely described,and several studies show contrasting results,primarily when investigated under in vitro conditions. According to Ahmad et al.,who investigated the in vitro growth processes of Stevia rebaudiana, it was presumed that water deficiency induced by PEG at a critical level led to the manipulation of plant physiology and biochemistry. Changes in the cellular environment can result in stress stimuli affecting cellular receptors and further triggering signal cascades involved in physiological, and therefore growth processes. Another explanation by Khalid et al.  refers to an increased carbohydrate and mineral content including K, N, and P under PEG addition, which enhanced the growth parameters of Pelargonium odoratissimum. This could also explain the results of our study, as increased concentrations of carbohydrates were found in the +PEG treated plants for both cultivars and K levels, except for sucrose content in Agria. Similar to plant height and biomass, K deficiency negatively affected water consumption, as root growth is frequently reduced under deficient K supply. For Milva, water consumption increased in the first week after PEG addition in +K+PEG and -K+PEG plants compared to plants without PEG. This was not observed for Agria, where water consumption decreased in PEG-treated plants in both K supplies when osmotic stress was induced. In a study by Dorneles et al.,the stress responses of potato plants exposed to water deficit under osmotic and matric induction were investigated.

They observed a more negative osmotic potential in plants than in nutrient solutions containing PEG, suggesting that plants osmotic potential may promote an osmotic force and thus water uptake under PEG conditions. This could explain the briefly higher water uptake rates of Milva immediately after PEG addition for both K supplies, indicating cultivar-specific responses to osmotic stress. Maintaining water consumption and general growth processes, despite stress situations, could therefore reflect a possible tolerance mechanism to osmotic and drought stress in Milva. At final harvest, the total biomass was lowest in -K-treated plants than +K plants for both cultivars. Sufficient K supply enhances photosynthetic processes, leading to increased leaf area expansion, which results in elevated biomass production  Milva produced more biomass during PEG-induced osmotic stress for both K treatments, whereas +PEG Agria plants produced a higher biomass only under -K, probably related to increased carbohydrate and mineral content, enhancing growth parameters. Overall, the biomass of side shoots was higher in -K plants compared to +K plants, in which the proportion of leaves was greater. Presumably, the plants under K deficit attempt to maintain the photosynthetic capacity by developing more side shoots to increase leaf biomass. Schittenhelm et al.  showed that potatoes can produce a large above-ground biomass as a strategy against soil water deficit. Accordingly,berry pots the increased biomass of side shoots in the -K+PEG plants could be the result of a similar mechanism to maintain biomass production under osmotic stress. This may as well be an adaptation to K deficiency, such that -K plants increased the leaf area by producing additional shoots, thus maximising the potential for additional photosynthetic activity. However, berry pots the cultivars used in this study could be divided according to their shoot morphology, which is based on genotypic characteristics. Cultivar Agria, used in our study, belongs to the stem type,supporting the results of stem biomass for +K plants, which was higher than that in Milva.

In contrast, Milva belongs to the intermediate type and equally forms both stems and leaves. Therefore, the increased biomass production of side shoots could be an adaptation to the prevailing conditions. Another reason for the high production of side shoots could be due to the experimental arrangement, as under greenhouse conditions light was available from all sides and the plants had enough space to spread out, which is usually not the case in the field due to narrow plant spacing. Reducing sugars accumulated more in -K plants than in +K plants.Since K is involved in phloem loading,impaired sucrose transport from source leaves to sink organs is a result of K deficiency. Compared to +K plants, reducing sugars accumulated more in the roots of -K plants. This is in accordance with Sung et al.,who found high concentrations of sugars in the roots of tomatoes grown under K deficient conditions. However, compared to the concentration of sugar in the roots, more reducing sugars were accumulated in the stems of the -K plants, which, in turn, could indicate an inhibited sugar transportation. Overall, the influence of PEG-induced osmotic stress also tended to affect the sugar concentration. Thus, +K+PEG and -K+PEG plants produced more sugars compared to plants without PEG addition. However, +K+PEG-treated Agria plants were an exception, suggesting that Agria is less susceptible to osmotic stress and may also be less susceptible to drought stress under optimal K supply. This also confirms the classification from different studies, where Agria was considered a more tolerant cultivar to drought stress under pot and field conditions. However, other studies classified Agria as sensitive to drought stress in a pot experiment  or as susceptible to water deficit under field conditions. Thus, there is no clear classification for Agria. In contrast, Milva was described as sensitive to drought stress  in pot experiments under greenhouse and under field conditions, which could not be confirmed in our study. The literature review showed that due to very different experimental conditions, an exact classification and a respective comparison is not easily possible. However, our investigation has shown that Milva and Agria can adapt to PEG-induced osmotic stress under hydroponic conditions. These strategies could also be used when adapting to drought stress under field conditions. Comparing matric and osmotic stress, Dorneles et al.  found that stress responses to both forms of stress were similar. Accordingly, the results from the hydroponic system may be applied to field conditions.Leaf samples at three different growth stages during the experiment provided detailed information on the physiological and physiochemical processes under altered conditions induced by sufficient and deficient K supply, and by PEG-induced osmotic stress. The K content in the leaf was positively influenced by the K supply, so that three-fold more K was detected in the leaves of +K plants compared to -K plants.

Climatic conditions must be also similar in order to compare results and would clearly affect production in other locations. In fact, the hours of inbound radiation and the fluctuations in temperatures can limit the use of some crops and affect the growth of the plants. Water temperatures also condition the growth of the fishes. In areas such as Seville, with a clear seasonal difference in temperature and solar radiation on plant production in aquaponics, the large variations in monthly production can condition the supply of food of aquaponic origin. The results of this study in Seville, located at 37◦ of latitude and with two periods of heat and cold that could limit aquaponic production, are similar to those obtained by Somerville  in the areas between Israel, Gaza and West Bank that are located at 32◦ latitude and with similar climatic conditions, although probably having less cold temperatures in autumn-winter. In another study, in Palermo,at 38◦ of latitude with a somewhat milder climate due to the influence of the sea, an average of 2250 lettuce heads  were produced in 5 m2 of cropping area at a very high density. Considering an average of 165 g per lettuce head, the production per growing area unit was 74.25 kg m− 2. This harvest obtained is strikingly high,but the authors do not detail information on the annual range of water temperatures in their MAS, nor how they achieved a sufficient biomass of tilapia from October to March to maintain such a high lettuce production at low water temperatures. Love et al.  produced a variety of vegetables during two years in Baltimore,using an aquaponic facility  with tilapia.

They obtained a plant production of 22 kg m− 2 in the first year and 31.5 kg m− 2 in the second. Those results are more consistent with ours. Regarding the fish growth indicators, the AGR 1.3 g d− 1 in MAS1 and 1.7 g d− 1 in MAS2 was higher than that of Delaide et al.. The FCR in our study,lower than those reported by Effendi et al. ,are in line with other authors: 1.29,1.16  and 1.56. The type of stocking method proposed in this study allowed obtaining 5 harvests of tilapia in MAS1 and 4 in MAS2 over 1 year, similar to the results cited by Sommerville et al.  with a staggered stocking method, stacking flower pot tower with fingerlings restocked each three months. Asciuto et al.  also used the staggered stocking method, but with two rounds of stocks in 1 year, also maintaining a higher fish biomass by having 2 tanks of 500 L each. This strategy was not adopted in our study because we believe that one single fish tank with only a batch of fish makes the MAS be more easily handled. The high biomass of fish harvested in summer as a precaution against high temperatures, reduced the fish biomass too much during autumn winter, which limited the plant production and also prevented any harvest of fish in this period. A better strategy in climates like those of Seville would be to increase the aeration in the water in the fish tanks during summer, instead of reducing the biomass. This would enable reducing the second August harvest by half, to 5 kg of fish, and the remaining 5 kg would accumulate to increase biomass during autumn winter, allowing a harvest during this period. In addition, there would be a surplus biomass of tilapia that, after 1 year of growth, would not exceed 350 g. These fish could join the annual restock of another 110 fry in the second year to start a new cycle of aquaponic production with a higher biomass that maintains a higher level of nutrients in the water for the plants.The combined production of fish and vegetables also has an influence on the inputs required. For instance, the water requirements in this type of systems are much lower than those for conventional aquaculture.

The average water replenishment rate calculated in our study  was lower than the 3.6 % reported by Delaide et al.,similar to that observed by P´erez-Urrestarazu et al. and in the lower part of the 0.5–10 % range determined for aquaponics by Love et al.. Considering the total plant production of the systems and all the water volume consumed, the average water footprint for the vegetal produce was 64 L kg− 1 in MAS1 and 91.3 L kg− 1 in MAS2. These values are lower than those obtained by Delaide et al.  and Love et al. and well below those reported by Delaide et al.. If the fish production is also considered, 53.7 L were needed to get a kg of produce in MAS1 and 78.4 L in MAS2. P´erez-Urrestarazu et al.  obtained a similar value in their best case scenario. In terms of energy consumption, the aquaponic facilities employed in our study required a very low amount of energy, as only the pumps and air compressors needed electricity. Hence, the average annual daily consumption was 0.86 kW h d− 1,very similar in MAS1 and MAS2. However, during the cold months, MAS2 presented a slightly lower daily consumption, while MAS1 increased to 0.91 kW h d− 1,due to the heaters that were sometimes necessary when the solar panel was not enough. Therefore, the energy consumed was really low: 1.6 kW h per kg of produce. In contrast, Love et al.  reported an annual electricity consumption around 10,900 kW h plus 8500 kW h in propane. Considering the joint production  that they obtained, 41.15 kW h of energy were required per kg of produce. In Delaide et al.’s  study, a much higher energy consumption per kg of produce  was observed, though the average daily consumption was lower. A value of 41.5 kW h kg− 1 was deduced from a study in much colder weather. The main difference of energy consumption between all these studies and ours was due to heating water, this being the most sensitive parameter in the aquaponic system. For example, in Delaide et al.  the submersible heaters they had to use  accounted for 57 % of the energy required. Conversely, Atlason et al.  showed a much lower energy consumption per kg of produce,as they used waste heat from a co-generation system for heating the system. Still, it was 5.5 times higher than in our study.

In light of this, it is clear that the strategies employed in our trial were successful as they produced a vast reduction in energy consumption. This is very important as energy costs are usually one of the most important factors for the viability of aquaponic production. The labour required for the operation of these systems is not high in relative terms as an average of 14− 18 min per day were necessary. However, an annual workload of 100− 120 h has a high cost if the MAS are not self-managed.The human population worldwide currently exceeds 7 billion, and it is projected to reach 8.5 billion by 2030, and 9.7 billion by 2050. With a fast growing global population, the demand for soil and land for crop production is likely to increase, and more urban area development is projected to take place. Earth’s arable land is finite and challenges such as soil degradation, water scarcity, and urban area development need to be addressed by developing new and modified agricultural systems. Alternative food production systems that require limited land, soil, and water, and which can be developed in urban areas may play a major role in future agriculture. Hydroponics and aquaponics are soilless agricultural systems that are highly productive, suitable for urban areas, and can address the shortage of land in relation to growing demand for food production. Hydroponics is the culture of plant crops in soilless water-based systems, where nutrients come only from formulated fertilizer. Aquaponics, is an integration of hydroponics and aquaculture, where crop plants and aquatic species can be grown together in a soilless water-based system. Aquaculture is growing of aquatic animals/organisms in a designated water body. Large amounts of polluted water are produced in aquaculture systems with a potential for environmental pollution,which can be reduced by techniques such as aquaponics. 

Aquaponics, a combined culture of fish and plants has been proposed as a means to decrease waste accumulation from aquatic monoculture and to increase the productivity and profitability of the system. Soilless water-based systems are commonly set-up in vertical integration systems in indoor urban settings, which addresses the limitations of soil quality and space availability. Being indoor practices, hydroponics and aquaponics are not directly affected by the changing climatic patterns and abrupt weather conditions, and hence could be effective adaptive strategies, as well. Aquaponics has several advantages over aquaculture and hydroponics. This system reduces the need for formulated fertilizers, eliminates the possibility of agricultural run-off, and cleanses the water through bio-filter treatments. The nutrients released from fish excreta and microbial breakdown of organic wastes are used by plants in aquaponic systems. This way the plant component serves as a bio-filter, and therefore a separate bio-filter is not needed unlike aquacultural systems. In addition, this bio-filter also generates income through the sale of the economic plant products. Therefore,ebb and flow the aquaponic systems develop an economically advantageous symbiotic system, where aquatic species and the plant component benefit each other and the grower receives two marketable products. In contrast, the crop plant is the only marketable product in hydroponics and it is devoid of the commercial aquatic species and associated nutrient supply. Aquaponics can also be a strategy to combat water scarcity, as it has been shown to lower overall water consumption  and prolong the useful life of water by reducing turnover rates and subsequently the environmental pollution, with improved economic return. Primarily, fishes are used as the aquatic species in aquaponic studies and the potential for other commercial species such as crayfish  are little known. Crayfishes have high economic importance globally, including southern United States and Southeast Asia. However, very few aquaponic studies have incorporated crayfishes and observed plant animal interaction effects. Effendi et al.  observed that spinachaquaponic systems resulted 5% higher crayfish survival rates than crayfish monoculture. They concluded that plant bio-filters such as spinach, is very effective in cleansing the water resulting better crayfish survival. Crayfish can also be grown together with common fishes under aquaponic systems. In Louisiana, cultivation of crayfish  and rice  together increased yield for both. Gallardo-Collí et al.  reported that tilapia cohabited with crayfish  in an aquaponic system that produced 9.4% higher green corn fodder  compared to hydroponics. Selection of plants for soilless systems is critical.

Basil  is an annual herb that is commercially important and both fresh and dried leaves are used for culinary purposes. Basil is considered a medicinal herb  for its diuretic and stimulating properties and also used in perfume compositions. Basil is suitable for soilless production, and several studies have used basil as aquaponic or hydroponic crop.Rakocy et al.  reported that aquaponic basil produced higher yield  than field basil. However, no studies have compared aquaponics and hydroponics systems for basil production. Hydroponics and aquaponics are emerging fields of alternative agriculture with the potential to address the contemporary challenges faced by traditional agriculture. However, of the few studies that have compared these two systems, mostly focused on the commercial aquaponic species and little information is available on the plant production dynamics. In addition, little is known about the potential for non-fish aquatic species such as crayfish. We conducted a greenhouse study comparing crayfish-based aquaponic systems to hydroponic systems with a focus on the basil plant. The parameters under study included basil plant growth, yield, quality, and nutrition.Water pH and water temperatures were measured twice weekly and daytime greenhouse temperature was collected daily. Water nitrogen  content was measured weekly using freshwater aquarium master test kit. Weekly basil leaf chlorophyll content was measured using SPAD 502P chlorophyll meter. In each plant a lower leaf and an upper leaf were measured in full sunlight and then averaged. Leaf chlorophyll content is a reflection plant health/quality  and hence, the SPAD readings are commonly used to determine the health quality of plant. Plant height  was measured every week using a standard ruler. Harvesting of basil plants took place on November 19, 2015.

Starting from the lowest line in Figures 10, it is shown that a poor P:N ratio results in significantly lower efficiencies than the other combinations, for all levels of variation. The NFT system, with its lower system volume, shows the highest sensitivity to variation . The 3000 m2 HPS scores lower than the reference due to its relatively low fraction of nutrients supplied by the fish . The addition of the RO system for a 2500 m2 HPS resulted in only a small performance difference with the reference , due to the low availability of nutrients in the RAS when demand is high in summer. Therefore, RO has limited added value in northern latitudes. The scenarios with buffer show very low sensitivity to transpiration variation, of which an AD buffer for the NFT system shows the greatest performance increase . For the DWC system, the AD buffer outperforms the RAS to HPS buffer, despite requiring less than a sixth of the volume. The production of tomatoes was also simulated and briefly explored to support the theories brought forward in this study. The corresponding methods, results and discussion can be found in Appendix 5. For a tomato crop, a similar decline in AP efficiency is found with increasing variation in the seasonal transpiration. However, the changes in the greenhouse parameters resulted in a smaller difference in variation than with lettuce. Most of the GH parameters tested in this study had only a small effect on the transpiration variation and could, therefore, be readily changed to save energy. This includes the thermal insulation of the cover, minimum temperature, heat storage, and screens, as shown by the smaller differences in transpiration in figure 6.

Further increasing the bounds of maximum humidity lowered the performance of the aquaponics system the most and is,potted blackberry plant therefore, not advised for low volume systems. In agreement with Dijkgraaf et al. , it is in most cases better to have a system that requires supplementation rather than dilution. For scenarios with a high CV as a result of energy savings, an increase in the HPS area is a suitable measure to decrease dilution requirements, with an acceptable loss in nutrient self-sufficiency . The same can be seen in the outcomes of Goddek & Körner , where the HPS area is increased relatively more than the decrease in transpiration rate between the different scenarios.The addition of a buffer for the direct flow from the RAS to the HPS reduces the variation in this flow, which leads to a significant increase in performance compared to the reference . However, the volume required to have this effect is substantial, with more than 10L/m2 required for each percentage point of performance increase. The buffer for the AD output has shown similar benefits with a much smaller volume of 0.6 to 0.75 L/m2 for an increase of one percentage point, which greatly reduces the estimated construction costs. The AD to HPS buffer increases performance by linking the nutrient supply to the seasonally variable demand. While this mainly influenced phosphorus, the NUE of N was also improved in some scenarios due to lower dilution requirements from phosphorus peaks. The RAS to HPS buffer flattens the peaks of NO3 in the RAS, which is especially beneficial for sensitive fish. It is not yet studied how the water quality is affected by the long term storage suggested here. This concerns both food safety aspects, as well as chemical reactions that could change the nutrient composition during storage.

It is expected that both chemical and microbial reactions continue in the storage tank, which could decrease the water quality and safety . If required, several adjustments can be made to lower the risk of pathogens in the storage tanks, such as temperature and pH control and disinfection. buffering the brine flow of the RO system was not explored in this study, but we expect a similar increase in performance as for the RAS to HPS buffer. While not only resulting in a more concentrated inflow than buffering RAS water, and thus a smaller required buffer, it would allow the RO to be activated more during the winter. This is when the nutrient concentrations in the RAS are generally the highest, while RO cannot be used as it would result in a nutrient surplus and subsequent dilution in the HPS. buffering the brine flow could likely flatten the nitrate peaks displayed by Goddek & Körner .The scarcity of freshwater in most countries is an increasingly acute problem, particularly as their populations continue to grow rapidly and place higher demands on water resources. The agriculture sector is the largest consumer of water supplies. Agriculture consumes about 87% of the total water consumption in the Middle East and North Africa region. In the Palestinian territories, the total estimated water used for agriculture is not exceeding 150 million cubic meters annually. This amount represents 45% of the total water consumption, which is reflected directly on the limited prospects for the development of irrigated agriculture that can have an important economic, social and political role in rebuilding the Palestinian economy. Wastewater has to be reclassified as a renewable water resource rather than as a waste.Reclaimed wastewater is a treatment of different types of wastewater for reuse application.

The climate change affect in the reuse application. Climate change affect directly or indirectly on the wastewater reclamation and its reuse to conserve freshwater resources. The direct climatic factors include temperature, precipitation, sea level rise and severe conditions, whereas the indirect factors related to management and operation activities as water use control, greenhouse gases and adaptation measures. Epuvalisation is a French word that means a biological treatment technique that comes from the contraction of two French words: épuration  and valorisation ; it uses plants,not only to purify water but also for the growth and production of these plants. The plants roots act as a physical filter which holds the suspended matters. Epuvalisation has been applied with ample success in many Mediterranean countries and in Belgium as a tertiary purification process of secondary treated effluent utilizing different plants. The technique was applied for treated wastewater. In addition, it was used for Sr/ Cs in wastewater treatment. This technique consists of hydroponic plantation in channels. The wastewater flows into the channels and keeping a direct contact with the plants’ roots. The roots are utilized as bio-filters and adsorbents for the removal of nitrogen, phosphorus and other macro-nutrients. In addition, toxic elements and salts can be removed from wastewater  by an accumulation into the plant tissues. The system mechanism consists of gravitational effluent flowing through open channels to keep the water well aerated. The channels host the plant roots not only for water absorption purposes but for trickling and biological filter functions as well. The roots play a dominant role in taking up the nutrients, thus decreasing the total dissolved solids, which includes nitrogen and phosphorus.

This technique can be operated in closed or open loop modes. The open loop system is less efficient in the removal of nutrients and salinity due to minimal contact time, while the closed loop system is more efficient because of a relatively longer retention time. The system can also produce two valuables, water and plant valorization. Water valorization which is the complementary treatment can make the water suitable for non-restrictive irrigation and plants valorization in which the system will produce. Valuable plants ; seed; animal feeding under given and strict conditions regarding toxic compounds such as heavy metals or any other compounds that could enter the food chain. In our lab, we have investigated the Rosemary plant using the same technique and same water type. The results emerged from this study demonstrated a good adaptation with increasing rate of all plant growth parameters. The technique was applicable using brine water for Basillicum irrigation which highly adapted in brine water and biomass production. The aim of this experiment was to investigate the ability of geranium plants to purify a secondary treated wastewater using Epuvalisation technique in greenhouse environment. The main objectives of this study were to plant geranium plants in epuvalisation system using secondary treated wastewater and fresh water and to determine the plant growth parameters and plant tissue analysis during and at the end of the seasons. The physical, chemical and biological analysis for influents and effluents of both secondary treated wastewater and fresh water as blank are determined during the study period. Comparison of the plan parameters between the two irrigation systems is used as a tool to determine the efficiency of the use of secondary treated wastewater in epuvalisation system.At the end of the experiment, the plants were harvested and separated into roots, leaves and stems and then dried in the air. The dried samples were used for chemical plant tissue analysis. The chemical analysis included total nitrogen, total phosphorus, sodium, tall pot stand chloride and potassium. A standard method for soil and plant analysis was used for chemical plant analysis.The results of the Irriblend-DSW simulations offered valuable information for the fertigation management of the demonstrative case studies presented, in which DSW and conventional waters with different quality, price, and availability are used. Once the requirements and available resources for the production systems were characterised, the DST could identify which combinations of water and fertiliser could be viable from a technical and economic perspective.

Both case studies involve intensive production systems with great land and water productivity,but with substantial investment and operational costs. The DST provides the value of PPI  for all technically feasible combinations, but only those with a PPI above the profitability threshold  would be economically feasible. For the NFT lettuce case, the DST showed that only half of the technically viable options were likely to be profitable,whereas for the GH tomato, all the solutions were above the profitability threshold. However, the real contribution of the DST is not merely filtering out unfeasible options from an economic perspective but also to offer information on how to optimise the use of available resources and maximise profits. Navigating the interactive plots,it can be seen that in both cases, increasing the amount of low-quality water  over the optimum percentage drastically reduces the PPI. In fact, the EC of the optimal solutions was close to the crop salinity threshold, since maximal addition of cheaper brackish water substantially reduces costs without  yield loss. In the NFT lettuce case, this limit was 35% of brackish water in the blend, as percentages over it rendered the crop non-profitable. This implies that, because the availability of conventional fresh water is becoming very scarce, without the supply of DSW, production would not be viable. In the case of GH tomato, although all solutions surpassed the profitability threshold, the DST showed that adding more than 65% of brackish water in the blend causes the EC to increase above the salinity threshold, which can result in a decrease in net profit over 2 × 103 €/ha/cycle. It is important to note here that, for the calculations, we used the mean GH tomato market price  in the 2017–18 season. For a crop market price below 0.45 €/kg,we would have found combinations with the PPI below the profitability threshold among the technically viable ones as in the case of NFT lettuce. Supplementary material related to this article can be found online at doi:10.1016/j.agwat.2021.107012. Information about fertiliser selection and cost for each water blend derived from these simulations was relevant for fertigation management. In both cases, the data showed that the amount and type of fertiliser required increased as the percentage of DSW increased in the water blend. However, this cost increase is lower than that owing to the DSW cost. The increase in fertiliser cost was approximately 0.06 €/m3 for both the NFT lettuce and the GH tomato when moving from 35% to 85% of DSW in the water blend, whereas the increase in water cost was over 0.22 €/m3 in the said percentage range. Therefore, notwithstanding that fertilisation programmes and even systems require adaptation to DSW, the fertiliser cost overrun derived from the integration of DSW did not seem to pose a major threat to profitability.

Ebb and Flow involves flooding the plant tray with the nutrient solution using a pump that is connected to the solution tank at given time intervals with the use of a timer. The solution is later drained back to the nutrient tank. Adoption of hydroponics in East African countries like: Uganda and Tanzania, where this technology might offer a profitable agri-business and food security solution for urban dwellers by tapping into the growing demand for local produce, is still very low.It is likely to be more complicated to provide sufficient food for the fast-growing population using traditional agriculture in future, therefore soil-less cultivation is the right substitute technology to adapt effectively.There has also been a lot of attention given to urban agriculture among researchers, scientists and the general public which calls for more attention into hydroponics as it is considered an urban farming technology. Based on the impasse of challenges presented by conventional farming practices, urbanization and the increasing urban population as well as the ability of hydroponics to tackle these challenges, this study focused on examining the status and perception of soilless farming in Central Uganda and Northern Tanzania as an alternative sustainable cropping system to increasing food security and agdribusiness opportunities around urbanand peri-urban areas. Focus was specifically put on a couple of influential factors majorly socio-economic and agricultural factors surrounding the urban and semi-urban farmers and farms practicing hydroponics in these countries. The study assessed and categorized the benefits,fodder sprouting system challenges and recommendations for enhancing the implementation of this technology. It focused specifically on vegetable production because research has shown vegetables to be one of the most easy-to-cultivate crops under hydroponics as earlier mentioned.

The study was carried out in the months of April-July 2021 in the urban and periurban areas of Meru district located in Northern Tanzania and Wakiso district located in Central Uganda. Tanzania and Uganda are both located in East Africa and experience tropical climate conditions. Tanzania has an estimated population of 58 million while Uganda has approximately 44 million people. Northern Tanzania was selected as study site because it is one of the vegetable growing hot spots in the country and also has a couple of large hydroponic farms in the country while the Central Uganda was selected because it has majority of the urban and periurban farmers engaging in soilless farming. A total of 150 farmers/firms/farms were identified using snowball sampling through farmers groups and recommendations from expert farmers and agricultural bodies. Only 51 participants who practice vegetable production soilless farming technology majorly hydroponics around urban and periurban areas took part in the study. These participants included both farm owners of the hydroponic vegetable farms that as well as managers of firms that produce vegetables using hydroponics for either seed production or vegetables for sale.The biggest challenge reported was the high investment costs required to set up this high end technology especially for the fully automated greenhouse farms . This was also noted by Nicole et al. who identified high startup costs as a challenge for adoption of hydroponic farming technology. These costs include: greenhouse construction, costs of fertilizers, electricity for system installation, hydroponic equipment such as: PVC pipes, hydroponic net cups, climate monitoring systems among others. Artificial lighting, for instance through use of Light Emitting Diodes lights is sometimes deemed necessary for steady production making energy costs a key factor . The dependency on electricity is one of the factors that make hydroponics expensive . As earlier noted, majority of the farmers interested in the farming system adopted it at a small scale under non-controlled environments to cut down on the high initial costs needed for setting up the hydroponic units.

The development of low cost and easy to use hydroponic units will not only increase adoption of technology but also help farmers produce high quality vegetables . 22% of the farmers still reported that hydroponic farming requires enough technical knowledge which also continues to deter farmers from adopting the technology. For example: knowledge on the right amount of nutrients required for a particular crop, how to mix them, in what proportions and recycling. Majority of the respondents reported having learn about hydroponic farming using internet which further corelates with the high number of educated participants of the study. Controlled environment hydroponics requires some knowledge on how to run the climate control system within the green house for factors such as: humidity, temperature etc.… The need for technical knowledge for hydroponics such as: maintainace of PH and EC maintainance is one of the challenges of hydroponics . 6% of the farm operators who practiced hydroponics using high end technology such as: climate control systems accordingly reported a hitch related to maintainace of EC, PH and temperature of the nutrient solution and damage to crops in case of system failure. A failure or mismanagement of hydroponics can cause crop damage as also noted by Specht et al. who indicated that it is not sustainable if not well handled. 12% of the farmers stated that lack of adequate ideas or innovations on use of alternative locally available resources for hydroponic farming is a setback for the adoption of the farming system. For example: replacement of PVC pipes with buckets or bottles for growing hydroponic vegetables. Lack of adequate options of organic fertilizers for hydroponics in agricultural shops was another drawback surrounding hydroponics mentioned by approximately 20% of the respondents.

Other challenges reported by 9% were: bias from the community for hydroponic produce who consider them to be non-organic products, lack of variety of organic fertilizer alternatives and the timeliness needed by the system to avoid crop or system failure. Fig. 6 shows the drawbacks of hydroponic farming in Tanzania and Uganda. Fig. 7 reviews the advantages and disadvantages of hydroponic farming among urban and semi-urban farmers in Uganda and Tanzania while Fig. 8 further summarizes the recommendations made by the respondents which can assist increase the adoption of the technology among the two countries and Africa at large.Fresh green vegetation or fodder is an essential input that plays a significant role in animal feed. Fodder in the form of sprouted grains such as barley, wheat, maize, alfalfa, oats, millets, rye, sunflower seeds, and lentils can be grown in an environmentally controlled system. Commercial hydroponic fodder companies report that about 6-10 kg of fresh fodder could be produced from 1.0 kg grain within 7-10 days in controlled spaces with hydroponic techniques by providing suitable temperature, humidity, and light in the growing rooms. Hydroponic fodder production is a primitive technique that started in the 1800s or earlier. The basic principle for the hydroponic fodder system is that cereal grains respond to water or nutrients rich solutions for germination as well as growth to produce green plants in the short time of 6-9 days. This system has no chance of soil-borne insects, pests, disease attacks, and weed infestation because nutrients are directly fed to the roots and plants placed in trays of different dimensions. The interest in controlled environment fodder production is being revived due to the shortage of green fodder for livestock production in extreme climates. Also, water scarcity and food production needs on arable land motivate farmers to produce fodder in a controlled environment . Most Middle Eastern and African countries have a severe shortage of food supplies for livestock due to repeated drought and lack of water for irrigation. A recent report from the Food and Agriculture Organization of the United Nations indicates that global food production needs to be increased by about 60-70 % from the current levels to meet the increased food demand in 2050.

The livestock sector has made significant contributions to ensuring global food security. Milk consumption and meat production from livestock are increasing worldwide due to expanding the world population and better living standards. Worldwide milk consumption is expected to grow from 664 million tons by 2006 to 1077 million tons by 2050, and meat production will increase about twofold from 258 to 455 million tons. According to FAO, about 30% of world croplands are used for livestock feed production. Over 63% of arable land in the European Union produces animal feed instead of food for people. Fig. 1 shows the breakdown of global agricultural land use in pasturing, animal feed production, and human food. More than 70% of agricultural land is used for some aspects of livestock production, which contributes 14.5% of human-induced greenhouse gas emissions from feed production and enteric fermentation from ruminants. Therefore, fodder production in agricultural land is a conflicting issue in countries with food shortages; cereal grains, rice, oil seeds, and pulses on arable land are critical to ensure the food security of the increased population. An innovative approach for fodder production could have significant potential in reducing the carbon footprint in livestock production. Recent research showed that hydroponic fodder production in a shipping container could reduce GHG emissions by 7.4% compared with conventional farming for barley fodder production. A higher reduction could be achieved with improved seed-to-fodder output. The open field fodder production for livestock is disturbed by the abrupt climate changes and consumes ample water. The dry matter content and nutritive value of fodder could be reduced due to the temperature rise and increased CO2 concentration in the atmosphere from climate changes. Schlenker and Roberts reported that maximum maize production could be achieved at 29.0◦C, but a further increase in temperature hinders the maize productivity. Lobell and Field reported that maize production could be decreased by 8.3% with every 1.0◦C rise in temperature.

Easterling et al. reported that every 4◦C rise in temperature could cause a 34% reduction in wheat production. Also,microgreen fodder system the livestock sector accounts for about 8% of global human water use; and the trend of global temperature rise could increase livestock water consumption by about two to three times. Hydroponic fodder production systems could save a significant amount of water and reduce reliance on traditional arable production. Some studies reported that the same amount of fodder could be produced with 35-45% lower costs using 0.5% of growing spaces. The water-saving with hydroponic systems could be up to 95% compared with open field production. Also, the nutrient compositions of hydroponic fodder are relatively better than grounded/open-field systems. Most importantly, fresh green fodder for livestock could be supplied 365 days a year, even in extreme conditions like high northern latitudes and arid regions . Therefore, fodder production in CE settings is becoming popular in recent years in developed countries like the USA, Australia, and Canada. Fig. 2 shows the different CE facilities used for green fodder production, like low-tech poly-house, small-scale shipping containers, and large-scale production in warehouses with precise control of indoor environments. Controlled environment agriculture facilities with optimal temperature, relative humidity , water, and lighting can produce green fodder within six to ten days. CEFP is an energy-intensive approach for maintaining suitable thermal environments with heating, ventilation, air-conditioning , and artificial lighting with highly automated systems. Although hydroponically grown fodder is a highly nutritious feed, the costs could be two to five times higher for the same DM from the original grain. These high operating costs are primarily associated with the energy use for HVAC, lighting, and high capital costs for the automated CE growing systems. Although the concept of hydroponic fodder production is relatively old, very few research works have been published. A few research studies have been done on feeding fodder to dairy animals in the United States; most fodder research is conducted in Australia, India, and some Gulf countries. Most research has been undertaken on nutritional aspects and operating costs regarding DM contents of fodder production compared with original grains. A study reviewed the nutritional elements of hydroponic fodder and their impact on productivity for milk and meat. The study also analyzed the water use efficiency in hydroponic production compared with open-field production. Other studies have reviewed the basic fundamental of hydroponic fodder production and rationality from water conservation, land use, and minimal use of chemicals and its benefits for animal production. Singh et al. reviewed the challenges, opportunities, and status of fodder production in India, mostly covering the open field fodder production.

Taken together, our findings of evolved isolates displaying altered biofilm formation and motility properties and the detection of mutations within genes related to biofilm formation and motility in single evolved isolates as well as across independent endpoint populations indicates that adaptation of B. subtilis to A. thaliana roots under the employed conditions is associated with alterations in these two bacterial traits. While we found that the phenotypic and genetic changes of Ev6.1 and Ev7.3 conferred a fitness advantage over the ancestor during root colonization, adaptation to one certain environment may be accompanied by a loss of fitness in other environments . This has been demonstrated for Escherichia coli which following adaptation to low temperature showed reduced fitness at high temperature . In the example of the evolution of hyper-swarmers of P. aeruginosa, the hypers warmer clones out competed the ancestor in swarming, but lost in biofilm competitions . In this study, we demonstrate that adaptation of B. subtilis to A. thaliana roots is accompanied by an evolutionary cost. When Ev6.1 and Ev7.3 each were competed against the ancestor in LB + xylan under shaking conditions, i.e. an environment where plant compounds are present but biofilm formation is not required for survival, both evolved isolates suffered a fitness disadvantage. The observation that two evolved isolates, from independent populations and with different phenotypes and genetic changes, both suffered a fitness disadvantage in a non-selective environment might suggest the generality of such an evolutionary cost accompanying adaptation to A. thaliana roots. In our EE approach, B. subtilis was adapted to plant roots in the absence of other microbes. In the rhizosphere environment under natural conditions, B. subtilis is far from being the sole microbial inhabitant.

Instead, it engages in cooperative and competitive interactions with other members of the rhizosphere microbiome. We tested whether the evolved isolate, Ev7.3, displaying increased root colonization in the selective environment relative to the ancestor, would also show improved establishment on the root under more ecologically complex conditions. We found that in the presence of a synthetic, soil-derived community, Ev7.3 displayed enhanced establishment on the root compared with the ancestor in two out of four inoculation ratios. This enhanced establishment on the root by Ev7.3 is not expected to be caused by altered antagonistic activities toward the community members. First,hydroponic bucket no major changes in the inhibition of the community members were observed in confrontation colony assays. Secondly, an increased number of Ev7.3 cells on the root did not cause a reduction in the co-colonizing community. Finally, Ev7.3 did not harbor mutations in genes directly related to secondary metabolite production. Instead, enhanced establishment on the root by Ev7.3 in the presence of the community is possibly enabled by robust biofilm formation facilitating stronger attachment to the root and enhanced utilization of plant compounds. Interestingly, a study by Molina-Santiago et al. showed that compared with a Dmatrix mutant, co-inoculation of B. subtilis WT with Pseudomonas chlororaphis on melon leaves enabled co-localization of the two species as well as the closer attachment of B. subtilis to the left surface . The robust biofilm formed on the root by Ev7.3 possibly facilitated by increased matrix production may thereby not exclude the community members on the root but could rather allow them to incorporate into the matrix. This could also explain why the enhanced establishment of B. subtilis Ev7.3 on the root did not cause a reduction in the number of community cells attached to the root. Alternatively, the community may not be majorly affected by any difference in the establishment on the root between the ancestor and Ev7.3 owing to the low abundance of B. subtilis relative to the community. Further work is needed to elucidate the interactions between B. subtilis and this synthetic community during root colonization. In summary, these findings suggest that even though B. subtilis was evolved on A. thaliana in the absence of other microbes, it became highly adapted to the plant root environment enabling better establishment on the root also when the ecological complexity increases.

How genetic adaptation to the plant root in the absence of other microbial species differs from adaptation to plant root environments with varying levels of ecological complexity is the scope of future studies.From an applied perspective, experimental evolution of B. subtilis on plant roots represents an unexplored approach for developing strains with improved root attachment abilities for agricultural use. However, a biofilm-motility trade off as observed here may be undesirable when developing biocontrol agents owing to the growing evidence of motility as an important trait for bacterial root colonization in soil systems . The phenotypes associated with the adaptation of B. subtilis to A. thaliana roots presented here as well as the accompanying evolutionary cost and the increased root colonization also in the presence of resident soil bacteria highlight the importance of considering the selective environment if evolving PGPR for biocontrol purposes.Aquaponics is an agricultural technique that is touted as a promising alternative to solve the food and environmental crisis that the world faces today. As it is a combination of aquaculture and hydroponics , this technique can have high water use efficiency, and reduce the dependency on pesticides and fertilizers which adds to the sustainability of the system. This system has been shown to consume 50–70% less water compared to traditional agricultural systems, owing to its recyclability. Moreover, this system requires less pest control and has proven to be less impacted by harsh weather conditions, leading to yield increase. As we are moving towards the era of digital agriculture, efforts have been made to design physical prototypes for smart commercial aquaponic systems. Lobanov et al. has focused on proposing a new system for reducing the carbon and nitrogen content from fish waste to produce liquid fertilizer which is added to facilitate the growth of lettuce in aquaponic set-ups .

Karimanzira et al. introduced the concept of building an intelligent aquaponics system incorporating predictive analysis, system optimization and anomaly detection for maximizing productivity in commercial aquaponics through early fault detection . Mahanta et al. formulated a laboratory set-up as a prototype to grow soybeans in hydroponic solution using plasma activated water to decrease the amount of heavy metal uptake and optimize yield . Rau et al. designed a smart IoT based sensing and actuation system for growing rice by controlling the concentration of magnesium and nitrogen in hydroponic solution along with monitoring the environmental parameters of the greenhouse . A similar design was proposed by Dhal et al. using a smart IoT system for real time sensing and regulation of nutrients in commercial aquaponic set-ups depending on the season in which the crops were grown . Timsina et al. proposed the use of Machine Learning models to regulate nutrients for growing cereals in farmlands, but efforts are yet to be made for growing them in aquaponic set-ups .There have been recent advancements in the field of Smart Aquaponics which involve monitoring environmental parameters as well as plant growth through different Machine Vision-Based approaches in an IoT environment . Arvind et al. implemented an AutoML model trained with an XGradient boost algorithm, with 10-fold cross-validation taking into account the different sensor values recorded in the greenhouse and the fish count in the aquaponic tank which was extracted using the mask R-CNN image segmentation. This algorithm was used to control the triggering of the actuators in the system that in turn control the environmental parameters in the greenhouse; ensuring significant improvements in yield and water conservation, when compared with the conventional methods. Languico et al. did a comparative study of three ML estimators: K-Nearest Neighbours , Logistic Regression , and Linear Support Vector Machine , on the visionfeature extracted images of lettuce in a smart aquaponics set-up to monitor diseases that the crop may incur in its lifetime. A similar kind of study was done by Maleki-Kakelar et al. where multiple ML algorithms like linear and quadratic regression models, fuzzy systems and genetic programming was used to conduct regression analysis for improving urease activity aimed at strengthening the behaviour of soils . A study on images of lettuce leaves was conducted by Concepcion II et al. to detect diseases, wherein different feature selection processes were used to select the top four attributes for training the ML models .

A study on smart nutrient regularization for replenishing the Nitrogen, Phosphorus and Potassium content of the soil has been done by Ahmed et al. using genetic algorithms to provide the optimal level of nutrients needed for high production level of crops . Hiram Ponce et al. used a combination of Convolutional Neural Network for extracting features from tomato leaves along with a combination of Artificial Hydrocarbon Network as the dense layer to predict deficiency of nutrients in tomato plants . A similar kind of Deep Neural Network was implemented by Yadav et al. for apple foliar disease classification using Plant Pathology image data-sets . Nevertheless, limited research has been conducted on monitoring and regulating nutrient concentrations in the aquaponic solution using ML-based approaches. The current work focuses on building a ML algorithm that monitors the nutrient status of hydroponic irrigation water and outputs a recommendation system for regulation of these parameters. The main motivation behind this entire approach is to select the most important nutrients that need to be regulated in aquaponic environments depending on the output of Machine Learning classifiers trained on small data-sets. The main issues which one may face while designing such a data-driven approach has been discussed in the next paragraph. One of the major challenges with automation in aquaponics is the lack of sufficient data and the vast number of predictors that have to be used for making any inferences. This could result in what is referred to as the “Curse of Dimensionality” leading to the available data becoming sparse . Thus, it becomes extremely important to reduce the dimensionality of the data-set without losing valuable information. For this, stackable planters feature selection techniques become more relevant. To state a few, Recursive Feature Elimination and ensemble techniques such as the Extra Trees Classifier have proven to be highly effective. It is also equally important to check for the separability of the classes in the data-set. Many data visualization techniques like Principal Component Analysis and Multi-Dimensional Scaling plots can be used to understand how linearly separable the data is and what classifiers would be best suited for the purpose. Another major drawback especially in the case of small data-sets is the problem of “over-fitting” the data . Traditional ML and Deep Learning algorithms have a high probability of performing poorly on small data-sets.

A solution to this problem was suggested by Shao et al. who proposed deep Reinforcement Learning algorithms named MONEADD and did a comparative study with Knapsack and Traveling Salesman problem to design neural networks for different combinatorial optimization problems without much feature engineering which showed better scalability when distributed on multiple GPUs . On a similar note, to address this problem of over-fitting, Braga-Neto et al. proposed Bolstered Error Estimation method, which uses the same data for both classifier design and error estimation . In this form of error estimation, the variance setting for the Bolstering kernel is determined in a non-parametric manner from the data. For all the linear classification rules, the integrals in the Bolstered error estimation are computed in the same way. For the non-linear classification rules, a small number of Monte-Carlo samples are generated. In this study, three types of Bolstered error estimators, namely the Gaussian Bolstered re-substitution error estimator, semi-Bolstered re-substitution error estimator, and the Gaussian Bolstered Leave-One-Out error estimator, have been used with linear classifiers like LDA and SVC, along with non-linear classifiers like CART and KNN, and their results have been compared to identify the best performing classifier in this case. Based on the performance of the classifier with utmost optimal performance, a set of recommendation rules were prescribed and a comparative study was done on how this proposed Machine Learning based approach resulted in more optimal yield as compared to the baseline model.The data-set which was used in this case was recorded from three commercial aquaponic facilities located in Caldwell, Bryan, and Grimes counties in Texas, USA which are large producers of lettuce and other greens.