Organic producers in Minnesota and North Dakota, USA, indicated that they wanted to participate in hard red spring wheat (Triticum aestivum L. emend. Thell) variety evaluations. The objectives were to determine if a farmer–researcher developed scoring system could be used to rank wheat varieties for yield potential when grown in certified organic fields, identify views of organic producers about on-farm research, and identify the educational impact of the participatory variety evaluation process. Hard red spring wheat varieties were compared for grain yield at six locations on certified organic farms in Minnesota and North Dakota over a three-year period. A scoring system was developed and then used to identify the relative rank of adapted varieties for yield. Producers were asked to rank all varieties on a scale from 1 to 9, where 1 is lowest yield potential and 9 is highest yield potential. Producers were able to distinguish higher producing varieties as a group in 2003 and 2004. ‘Oklee’ a high yielding variety was ranked lowest in 2005. There was a significant linear relationship between producer ranking and yield (P<0.05) even though producers could not pick the highest yielding varieties consistently in the field. The producer survey showed that grain yield, protein content, wheat scab resistance, leaf disease resistance, early seedling vigor, test weight and canopy closure were traits producers valued most in a variety. Heading date, impact on succeeding crops, straw and stubble production were ranked lower. Multi-year variety evaluation on certified organic land was highly valued by the producers surveyed. From an educational perspective, the exercise was successful in that producers had to observe individual varieties carefully in order to come to a consensus producer ranking. The model of participatory research can be used for a variety of field research projects and field days.

In temperate regions, reduced tillage is still not broadly accepted in organic farming although the guidelines often recommend the reduction of tillage intensity. During the years 5–7 of a long-term experiment, we studied the effects of the three tillage systems moldboard plowing (MP, soil inversion to 30 cm depth), two-layer plowing (TP, inversion to 15 cm, loosening to 30 cm) and layer cultivation (LC, loosening to 30 cm) on soil nutrients, nutrient content of barley, rye and associated weeds, and yield on a clay loam soil. Crops were cultivated within a five-course crop rotation consisting of green fallow, winter wheat, field peas, winter rye and spring barley; no additional fertilizers were applied. Tillage affected only soil nitrate under barley, which decreased with decreasing tillage intensity. Soil humus, phosphorus (P) and potassium (K) were unaffected by tillage under both crops. Barley shoot nitrogen content was significantly influenced by tillage, with, across years, 38 and 83% higher values under MP than under TP or LC, respectively. Weeds in barley had a higher P and K content at LC than at MP or TP. This resulted, across years, in 73% higher barley yields in MP than in LC. The TP showed a 29% higher barley yield than the LC. Tillage methods had no effect on rye nutrient contents, rye yields or on weeds associated with rye. The significant interaction between tillage and year for rye yield suggests that weather conditions in a given year (e.g., amount of rainfall) can considerably alter the effect of reduced tillage.

Organic/biodynamic agriculture has been reported worldwide as a suitable system to conserve or even regenerate natural resources. Due to the lack of long-term studies regarding the profitability of tropical organic vs conventional farming, the economic performance of biodynamic vs conventional soybean was studied using data from a consecutive 7-yr case study in a farm with 48.4 ha of biodynamic soybeans in Paraná State, Brazil. Analyses of production costs and financial indicators were adjusted at updated values according to inflation in the period. Effective operational costs were 4.4% higher in biodynamic than in conventional farming. The biodynamic yields were lower (3.6%) than those of conventional. Prices were 57% higher in biodynamic than in conventional, making biodynamic farming more profitable than conventional farming, as shown by financial indicators (gross revenue, gross margin, net margin, net income and capital income were 50.7, 99.9, 122.9, 150.4 and 166.9%, respectively, higher in biodynamic than in conventional). The price equilibrium point (PEP) was 3.4% higher for biodynamic farming; the leveling point was 36.9% higher for conventional farming. Manual weeding and plowing increased organic costs. Higher biodynamic trading prices than those of conventional triggered a PEP suitable for covering higher costs and thus boosting profitability. Further investigations and policies are suggested to further improve biodynamic farming efficiency and sustainability.

Organic producers are seeking alternative tactics for weed control so that they can reduce their need for tillage. In this study, we examined cover crop strategies for suppressing weed growth after harvest of wheat. Three cover crop treatments, red clover (mammoth type), a mixture of oat and dry pea, and a control were compared. Treatments were established in both winter and spring wheat, resulting in six treatments arranged in a randomized complete block design. Red clover was underseeded in wheat by drilling in the spring, and the oat/pea mixture was planted in August. Oat was planted uniformly across all treatments in the following growing season. The red clover treatment effectively suppressed weeds, reducing post-harvest weed biomass, density of volunteer winter wheat, and seed production of downy brome by more than 99% compared with the control. Oat/pea was not effective for weed management, likely because of less fall growth and competition compared with red clover. Underseeding red clover did not affect winter wheat yield, but reduced spring wheat yield by 17%. Oat yield, however, was reduced by volunteer crop plants and downy brome infestations in all treatments. Underseeding clovers in winter wheat may effectively manage weeds and, if they winterkill, can replace the need for tillage to control weeds after wheat harvest.

With growth in retail sales estimated by industry at 15–25% yr−1, organic food represents the only significant growth sector in Canada's food system. This reality, in combination with mounting evidence that substantial environmental and economic benefits can arise from organic farming adoption, suggests that organic sector development should be a priority for governments. However, organic food remains a marginal component of Canadian agricultural and trade policy. This study was designed to examine the opportunities and costs to the province of Ontario of strategic investment in the expansion of the organic sector. Drawing on existing literature and Ontario land use and production data, the study used an iterative process to identify how the province could reach a target of 10% of Ontario's cropped acres in organic production within 15 years, from the current level of about 1%. We concluded that after 15 years 5343 organic farmers would be producing organically in all major commodities, including 4254 converting farmers entering the organic sector and 600 new entrants to farming. The 489 organic farms reported in 2004 would be included in this total of 5343 because we assume that they all make modest additions over this time period to their existing operations. Organic production would occur on about 367,000 ha of land, and some 1.4 million animals would be reared organically. After 15 years, these farmers would reduce fertilizer applications by about 43 million kg (saving $18.4 million yr−1), pesticide applications by about 296,000 kg active ingredient (saving $9.1 million yr−1), and 7079 kg of growth-promoting antibiotics/medications consumed in animal feed. This 30-point program would require new investments by the provincial government of about $51 million over 15 years. Phase I (first 5 years) costs would total $7.1 million and Phase II (following 10 years) costs $43.9 million. Net program costs would be significantly lower since farmers would have directly saved on inputs and received premium organic prices for most of their goods sold, thereby reducing government costs related to supporting farm finances. Additionally, this program would contribute significantly to reducing the externalized costs of current approaches to agriculture, conservatively estimated at $145 million annually or $2.18 billion over the 15-year life of the program. Not all those costs would be saved within 15 years, but this exceedingly modest investment in organic production, representing only 2.3% of these externalized costs, would generate savings in externalized costs far beyond this one-time investment. Implementation of this plan would allow domestic producers to capture 51% of Ontario's organic consumption, up from the currently low-range estimate of 15%. Organic foods would represent 1.9% of the total food retail market after 5 years and 5.3% of the total market after 15 years.

The literature implicates strongly that including energy supplements in dairy rations based on protein-rich forages increases performance and feed efficiency due to an improved and more balanced ruminal energy and protein supply. Therefore, both conventional and organic dairy farms primarily supplement roughages with concentrates, containing high proportions of cereal grains. However, considering the main principles of sustainable agricultural systems and nutrient cycles, the question of alternatives is raised. Therefore, the present study was conducted to compare grain and maize silage as energy sources in organic dairy cow rations. Two grass–clover silage-based diets, offered on an ad libitum basis, were supplemented either with 1 kg grain mixture plus 0.5 kg hay (treatment group G) or 2.1 kg maize silage (treatment group M) on a dry matter (DM) basis. The trial was carried out as a change-over design and lasted for 15 weeks. Intake of concentrates, DM and utilizable crude protein in the duodenum (uCP) were similar in both treatments. However, significant differences between treatments G and M were found for grass–clover silage dry matter intake (DMI) (13.4 versus 12.9 kg), forage DMI (14.6 versus 15.7 kg), crude protein (CP) intake (2885 versus 2801 g), ruminal nitrogen balance (RNB) (40 versus 29 g) and intake of neutral detergent fiber (NDF) (7630 versus 7900 g). Milk yield was not affected by treatment, but in treatment M, milk fat content was at 42.4 g kg−1, significantly higher, and milk urea concentration at 19.7 mg 100 ml−1, significantly lower, as compared with treatment G. Efficiency of N use (N in milk in % of N intake) tended to be improved in treatment M. Balances of energy and uCP (intake as a percentage of requirements) were unaffected by treatment.

Producers may be able to improve growth of cover crop mixtures by selecting species to occupy different levels (zones) in the cover crop canopy. This suggestion is based on a study where we compared four cover crop treatments, comprised of one, three, six and nine species, for biomass production. Oat, dry pea and oilseed radish were present in all multi-species mixtures. Treatments were established in August, following spring wheat harvest. Biomass was harvested 9 weeks later. The most productive treatment was the oat–dry pea–oilseed radish mixture. Species of this mixture occupied different zones in the canopy and minimized interspecies competition to improve production. Cover crop mixtures of six and nine species produced 24% less biomass, which we partially attribute to unequal distribution of species in zones of the canopy. This suggestion with canopy architecture could be tested further with other cover crop species to quantify its impact.

This paper is an historical analysis of how global pressures and aspirations have affected US farm bill debates over time, from the first farm bill in 1933 to the current debates over a 2018 farm bill. It focuses in particular on how nationalist and patriotic arguments have been used to support the USA's desired place in global agricultural markets over time. For example, debates over the 2008 farm bill reflected strong international concerns around both trade and energy, with early discussion focusing on keeping the USA ‘competitive’ as an agricultural exporter alongside emerging agricultural powerhouses, and later debates focusing on increasing domestic bioenergy production to ‘protect’ the USA from what were seen as risky energy imports. In other words, debates over trade and energy in 2008 provide insight into how stakeholders positioned the USA with respect to the rest of the world and how that positioning changed over the course of debates. But such questions about the USA's global aspirations—whether to maximize US production for export or protect US agriculture from global rivals—have been part of the farm bill since its earliest days. This analysis will examine how concerns over such national agricultural prominence in a globalizing context have played into and influenced the contours of domestic farm policy over time, with implications for the 2018 farm bill debates.

A vast amount of agricultural land in the USA will change hands in the coming years as established farmers age and transition out of farm ownership. As a result, beginning farmers are likely to continue to face numerous obstacles as they try to find and purchase the property. Two of the greatest barriers include the high price that farm property usually commands and the steady conversion of farmland to non-agricultural uses (e.g., suburban development). Non-profit organizations and government agencies have used conservation easements extensively to protect against conversion of agricultural land, but, too often, that does not ensure affordability for beginning farmers. Accordingly, advocates have developed supplemental land transfer tools intended to enhance conservation easements and help beginning farmers gain access to land. In this exploratory research, we look at two of these novel tools, namely Conservation Buyer Programs (CBPs) and the option to purchase at agricultural value (OPAV). Specifically, we present case studies about two entities that use OPAV and two that use CBPs in order to understand how these tools function and whether they improve land access for beginning farmers. Interviews with professionals and beginning farmers who have worked with these tools in four states inform our analysis and add depth to previous scholarship. We found that OPAV and CBPs can improve access to agricultural land for beginning farmers under certain circumstances. These tools, however, are not panaceas to the challenge land affordability presents, nor are they the only tools used by the entities we studied. CBPs alone have rarely been used to help new farmers; yet, they have been paired effectively with a conservation easement and OPAV. Additionally, we found a similar tool, the simultaneous sale, has been quite effective when paired with OPAV, and less costly than the traditional conservation buyer approach. All of these tools expand the land access toolbox in important ways, but given the paucity of existing scholarship on this topic, additional research is needed. Practitioners and researchers must think critically about whether these tools are the most effective instruments to employ in the effort to get beginning farmers on the land.

Recirculation of nitrogen (N) from crop residue and green-manure biomass resources may reduce the need to add new reactive N to maintain crop yield and quality. The aim of this study was to determine how different strategies for recycling residual and green-manure biomass influence yield and N concentration of the edible parts of food crops in a stockless organic cropping system. For this purpose, three biomass distribution treatments were investigated in a field experiment, based on a cropping system designed to produce both high-quality food crops and biomass resources from crop residues, cover crops and a green-manure ley. The three treatments, applied at the cropping system level, were: (1) incorporating the aboveground biomass resources in situ (IS); (2) harvesting, ensiling and redistributing the same biomass resources to the non-legume crops (biomass redistribution, BR); and (3) harvesting, ensiling and using the biomass resources as substrate for production of bio-methane via anaerobic digestion (AD) followed by distribution of the digestate as bio-fertilizer to the non-legume crops. The redistribution of ensiled (BR) and digested (AD) biomass did not increase the yield of the edible parts in winter rye (Secale cereal L.), white cabbage (Brassica oleracea L.) or red beet (Beta vulgaris L.) compared with leaving the biomass on the ground at harvest (IS). The BR treatment increased the yield of lentil intercropped with oat, compared with IS treatment in one of the two studied years. The total biomass yield of the cover crop following winter rye was significantly higher in the BR treatment than in IS in both years. The legume proportion in the green-manure ley was significantly higher in the AD and BR treatments as compared with IS in one of the experimental years. This study showed that strategic biomass redistribution has the potential to enhance biomass productivity while maintaining food crop yields, thereby enhancing whole system productivity. Biomass redistribution systems both with and without biogas digestion offer a new strategy for the development of multifunctional arable cropping systems that rely on internal nutrient cycling.

Extensive and semi-extensive production based on local swine breeds such as Majorcan Black Pig, Cinta Senese, Gascon, Krškopolje and Turopolje is becoming extremely rare and on the verge of disappearing in Europe. In this context, the main aim of this study was to assess the potential feasibility of marketing strategies to act as guidelines for stakeholders along the supply chain to create and improve added value and match market demands. The sustainability of five production systems was evaluated together with 60 stakeholders representing five local swine breeds, using a World Café (WC) method combined with an Analytical Hierarchical Process (AHP). The results showed that the proposed strategies could differ slightly depending on each system, while the product strategy was a common marketing priority for most of the stakeholders and represented all the systems evaluated. Diversifying production toward quality, innovative products, enhanced standardization, and quality labeling or seals of guarantee, such as the protected geographical indication or the protected designation of origin, would contribute to the sustainability of these chains. Advertising the storytelling of the meat products and emphasizing their healthier properties were also considered as positive strategies. To this effect, promotion should involve improving knowledge of the local systems and raising the profile of the meat products via public relations (networks, web pages, food and gastronomic events, workshops and so on) in the Hotels, Restaurants and Catering (HORECA) sector, stores selling top-quality products and local food shops. Better showcasing of these products and keeping the price in the premium segment would indirectly help the primary sector. By way of conclusion, other more developed local swine systems could be strong competitors, hence it is extremely important to effectively identify and trace all autochthonous swine breed products throughout the production chain. Furthermore, the entire chain must place greater emphasis on grazing (extensive or semi-extensive), the origin of the swine and their meat products. However, of utmost importance is cooperation between farms, firms and institutions.

Organic matter water extract, or so-called ‘tea’, may be used to correct nutrient deficiencies in crops or enhance their defense systems. Such tea mixtures are prepared locally by Mediterranean farmers to offset a multitude of constraints, particularly a scarcity of organic manure or high synthetic input costs. However, the diverse range of tea production and usage practices and farmers' underlying rationales have yet to be thoroughly studied. Yet locally they constitute real alternatives that allow farmers to maintain their income levels while reducing reliance on chemical inputs. The main objective of this study was to gain insight into farmers' rationale and practices regarding the production of homemade dry manure tea (HMT) in North Africa, while also highlighting the benefits perceived by farmers. Nearly 50 interviews with farmers were thus conducted in three irrigated cropping areas in Morocco, Algeria and Tunisia. Our results showed that HMT is widely used in intensified family horticultural cropping systems that usually rely on drip irrigation and chemical fertilization. The analysis of farmers' practices revealed that HMT was generally made from aged manure that was pure or consisted of a mixture of sheep, cow or poultry dung. The production protocol varied in terms of drenching techniques, maceration time, container volume and type, and filtration techniques. Farmers applied the derived tea via the drip irrigation system, regularly or with a limited number of applications. The analysis of farmers' rationales and perceptions regarding HMT clearly highlighted that they felt that these practices played a positive role. HMT was considered to improve vegetative growth, yield and, to a lesser extent, soil properties. These benefits could in turn lead to decreased use of synthetic fertilizers by farmers, while boosting their income. The increased understanding of HMT and the underlying rationales showcased in this study could help scientists better analyze and assess these practices in the future. The findings could also facilitate improvement and wider dissemination of these practices to achieve more sustainable irrigation systems in the intensified irrigated cropping areas that abound in North Africa.

Our global food supply becomes more vulnerable as we continue to lose diverse genetic resources. The Ossabaw hog is a feral breed that is unique to North America, a distant relative to the renowned Iberian hog and is considered an endangered swine breed. The objective of our farmer participatory project was to examine the meat and fat characteristics of Ossabaw hogs raised in alternative management systems for niche-market application. At one farm, eight Ossabaw pigs were randomly assigned to a grass pasture and fed a free choice corn–soy (CS) ration or placed in a mixed hardwood forest plot and provided free choice peanuts in the shells (P), alfalfa pellets (A) and mast from the mixed hardwoods (diet collectively referred to as PAM). The two diets had no effect on Ossabaw production data or pork quality characteristics; however, fat profiles were altered. Ossabaws weighed approximately 70 kg when harvested at 400 days and produced chops with small loin eyes (21–23 cm2) and minimal evidence of intramuscular fat deposits (1%). The unsaturated fatty acid (USFA) to saturated fatty acid (SFA) ratio improved from 1.6 to 2.6 (P<0.01) as a result of feeding the PAM diet. Forest-finished Ossabaw pork was considered more flavorful by food critics and renowned chefs than that of conventionally fed animals. Mast from hardwoods offers the possibility of enhancing pork flavor for niche markets and using a renewable forest resource as a food source. For farm two, eight Ossabaw gilts and eight crossbred progeny (from European breeds) were randomly assigned to one of the two dirt-lots and fed free choice a CS ration or PA diet (same ration as mentioned above with no mast). Ossabaw hogs grew nearly one-third as fast as the crosses and weighed approximately 80% of the crosses' harvest weight at twice their age. Loin eye areas of the crosses were nearly twice as large as the Ossabaws while the subcutaneous back fat deposition was nearly half. Compared to the CS diet, the PA ration decreased SFA by 23% while polyunsaturated fatty acids (PUFA) increased by 60%. The USFA to SFA ratios improved from 1.5 to 2.2 (P<0.01) when PA diets were fed. Differences (P<0.05) in USFA profiles were observed for breed effects; Ossabaws had 8% higher levels of monounsaturated fatty acids and 18% lower PUFA levels than the crosses. When adjusted for breed effects, no differences in sensory characteristics for the CS versus PA diets were detected by a trained panel. Ossabaws were more flavorful than the crosses (2.3 versus 1.6); (P<0.05).

Agricultural enterprises that are run on ecological principles receive, in some countries, higher levels of financial support from the European Union (EU) than other agricultural businesses. The aim is to provide an incentive for businesses to adopt organic farming systems, a change desired by both politicians and society. However, with a fixed system of support payments based on land area, increasing the proportion of farms being run organically leads directly to higher costs of subsidies for the EU and the individual countries. This becomes especially true if enterprises with large land areas, high turnover and high income are converted to organic farming methods. Because financial resources within the member states are in very short supply, a modification of the current system of subsidies would seem to be necessary in the near future. The aim of any new system should be to reduce profit windfalls without making a drastic reduction in the incentive effect of the current system. At the same time, businesses that can run along these lines on a sustainable basis should be especially supported. This requires an increased level of individual assessment of the potential of the subsidized enterprises in relation to their cost–performance ratio for organic agricultural production. In this connection, a partial change to profit-based tax systems can be used as an effective instrument for co-financing. The method used to calculate profits for tax purposes, which varies from state to state, can be used to assess the performance and success of the organic farmer. Tax-free allowances or reductions in tax rates could be used to provide a selective subsidy method. The ability to relate subsidies to performance, thereby reducing windfall profits, is not the only advantage of using the tax system for this purpose. Another advantage is the low transaction costs. Using the example of the offsetting of profits between time periods, it will be shown here that the tax system can be used as an additional instrument for subsidization. The existing methods of subsidy can only be supported in this way, not completely substituted.

Cotton and peanut grown under irrigation make up over 769,000 ha in the Southeast USA. The consumptive use of water for irrigation has significantly impacted groundwater resources, spring flows and streamflows in many parts of this region, particularly during severe droughts. This situation is further complicated with extreme weather events and climate variability. In this study, we compare yields and water use in a non-irrigated sod-based rotation system (SBR; bahiagrass–bahiagrass–peanut–cotton) to an irrigated conventional rotation system (ICR; peanut–cotton–cotton). Root mass of oat cover crop following peanut or cotton in a SBR and ICR system was also measured. A soil water assessment model (SWAT) was used to simulate irrigation water demands over a 34 yr period (1980–2013) under different soil types to quantify water saving potential of SBR. The average peanut yield in ICR from 2002 to 2013 was 4509 kg ha−1, while that in SBR was 4874 kg ha−1. Likewise the average cotton yield in ICR during the same period was 1237 kg ha−1, while that in SBR was 1339 kg ha−1. Oats had greater root mass in SBR than ICR. Simulation results indicate that crops in SBR consistently had substantially lower irrigation requirements (between 11 and 22 cm yr−1) than those in ICR in dry years. The water-saving potential of SBR varies positively with increasing sand content in soil.

Legumes such as white lupin (Lupinus albus L.) provide a valuable nitrogen source in organic agriculture. With organic farming hectarage increasing and white lupin interest increasing in the southeastern USA due to newly released winter hardy cultivars, non-chemical weed control practices in lupin are needed. A two-year experiment was established at two locations in Alabama. Five weed control practices were evaluated: one pre-emergence (PRE)-applied herbicide (S-metolachlor), two mechanical (hand hoed) and two cultural (living mulch utilizing two black oat cultivars) weed control treatments. Fourteen weed species were encountered. S-metolachlor provided above 80% control of most weed species present in this experiment. The cultivation treatments and black oat companion crops also provided good weed control of many of the weeds encountered. Crop injury of all treatments was low on a 0 to 10 scale with 0 representing no injury: <2.0, <1.3 and <1.2 by S-metolachlor, the cultivation treatments and the black oat companion crops, respectively. Grain yield of cultivars ABL 1082, AU Alpha and AU Homer were 1540, 1130, 850 kg ha−1, respectively, when treated with the conventional treatment, S-metolachlor. Grain yield in the organic treatments was equivalent. The cultivation treatments and black oat companions were successful alternative weed control practices in white lupin production.

Nearly all commercial sweet corn fields contain weeds that escaped management and, therefore, sweet corn often suffers yield losses due to weed competition. For this reason, field trials were conducted from 2009 to 2011 near Prosser, WA and Urbana, IL to evaluate the responses of weeds and four sweet corn hybrids to three levels of weed management; weed free, high intensity cultivation (HC), and low intensity cultivation (LC). Weed management level had the greatest impact on early season weed densities and HC reduced final weed biomass more than LC in 2 of 4 site-years. Two taller sweet corn hybrids with greater leaf area suppressed final weed biomass more than two shorter hybrids with less leaf area in 3 of 4 site-years. When grown with less intense weed management that resulted in more weeds, taller sweet corn hybrids with greater leaf area maintained yields better than shorter, less competitive sweet corn hybrids. Utilizing hybrids with greater tolerance to weeds and greater ability to suppress weeds could be a valuable component of an integrated weed management system.

With the advent of confined feeding systems and associated herd size increases, dairy farms have had to import more feed from off the farm, leading to on farm nutrient surpluses. Management-intensive grazing (MIG) is an alternative to confined feeding. Under MIG, the herd is rotated among small paddocks every 12–24 h for efficient conversion of forage into milk using grass pasture to provide most of the herd's nutritional needs. Previous research on MIG reported high concentrations of nitrate under grassed monolith lysimeters and grazed pastures. However, because of the high levels of nitrogen (N) fertilization and ponding of cow urine in lysimeters, these previous studies may have overestimated nitrate leaching losses from MIG systems as practiced in the mid-Atlantic region. To determine the extent of nitrate losses to groundwater under MIG in the mid-Atlantic, we sampled shallow groundwater biweekly for 3 yrs on six watersheds in three Maryland dairy farms, one confined and two MIG-based farms. Transects of nested piezometers and ceramic tipped suction lysimeters were installed in each watershed. Seasonal mean nitrate-N concentrations under the four grazed watersheds were generally lower than under the confined feeding farm watersheds and were generally below the widely used drinking water standard of 10 mg L−1. Average nitrate-N concentrations for all four grazed watersheds were between 4 and 7 mg L−1, while the two confined feeding farm watersheds averaged 7 and 11 mg L−1, indicating that the MIG system did not cause excessive nitrate leaching.

Green manure and compost-enriched in phosphorus can promote the sustainability of cropping systems by increasing soil fertility over the long term. They can also be used to manage crop/weed interactions, a key element in guaranteeing an appropriate level of satisfactory crop yields. We studied how green manuring with hairy vetch (Vicia villosa Roth.) and the application of different types of phosphorous-enriched compost affect weed/maize (Zea mays L.) interactions in an organic stockless Mediterranean agroecosystem for two consecutive dry years. Green manure stimulated the expression of maize traits related to a higher competitive ability against weeds, such as early growth, height and leaf area index, while the effect of compost was less clear. Regarding crop/weed competition, both green manuring and a phosphorus-enriched compost application gave a significant advantage to maize. Neither green manure nor compost increased total weed density and biomass compared to the control. Green manuring significantly affected the weed community composition. The relative density of ruderal and competitive-ruderal species (according to Grime's classification) was higher in plots where the green manure was applied. The use of green manure, together with novel composting techniques, significantly affected crop/weed competitive interactions, favoring maize, but also creating favorable conditions for unwanted weed species such as competitive-ruderals. Increasing nitrogen availability in the early growth stages of maize through green manuring can increase crop competitive ability. However, this may not suffice to preserve the system from future weed problems, should potentially detrimental species be selected. Dedicated strategies for the control of emerging weed species may thus be needed.