Legumes have been shown to enhance bioavailability of phosphorus (P) from sparingly soluble pools, yet this functional trait remains underutilized in agriculture, and is untested at decadal scales. Management and legume presence effects on temporal soil properties were evaluated in a 17-year field crop experiment using soil samples collected in 1992, 2000 and 2006. Management systems compared included: (1) conventional corn–soybean–wheat rotation (C–S–W), (2) organic (C–S–W+red clover), (3) alfalfa and (4) early successional field. To evaluate the effects of long-term management versus recent management (residues and P fertilizer) on P and bio-availability to soybean, subplots of soybean were established with and without P-fertilizer (30 kg P ha−1), and compared to subplots and main plot with the long-term system. We evaluated soil properties (C, total P, Bray extractable inorganic P, particulate organic matter phosphorus) and soybean P uptake, biomass and yield. Recent fertilizer P inputs had no detectable influence on soil P, and total soil P stayed stable at ~350 mg P kg−1, whereas inorganic P (Pi) declined from an initial value of 54 to an average of 35 mg P kg−1. A P balance was constructed and showed a net loss of −96.7 kg P ha−1 yr−1 for the organic system, yet Bray-Pi and soybean P uptake were maintained under organic production at similar levels to the conventional, fertilized system. Particulate organic matter P was 57, 82 and 128% higher in organic, alfalfa and successional treatments, respectively, compared to conventional. A similar pattern was observed for soil C, soybean yield and bioavailable P, which were 20–50% higher in the organic, alfalfa and successional systems relative to conventional. This study provides evidence that long-term management history influences bioavailability of P.

The shift toward post-productivist agricultural production in developed countries in recent decades has brought a growing focus on local sustainability and quality food production. This trend has been reflected in the development of a variety of alternative food networks and short food supply chain initiatives. In Czechia, the local and good-quality movement has been significantly represented by the boom in farmers’ markets during the past 2 years. The aim of this paper is to examine the actual potential of the Czech agricultural sector to supply the recently developed network of farmers’ markets. Even though these markets are generally considered to offer farmers better revenues than selling their products to big processors and retail companies, many Czech farmers’ market managers face a lack of potential vendors for their markets. Therefore, we ask if there are producers and self-processors of goods typically sold on farmers’ markets of the appropriate size and legal form in suitable locations in relation to the areas of the biggest demand. The quantitative approach applied was based on the national statistical data on the agricultural sector. It was used to develop a set of indicators which have been displayed in maps and further examined. The results show a high theoretical potential of the Czech agricultural sector to supply farmers’ markets because there are relatively many small farmers producing products sellable on farmers’ markets. In the Czech context, where the tradition of running independent businesses was interrupted by the country's communist past, the lack of experience with private entrepreneurship and marketing among farmers seems to be the main obstacle to broader involvement of farmers on farmers’ markets.

Foodshed analysis provides a way to assess the capacity of regions to feed themselves. While dozens of foodshed analyses have been completed across North America, they have not been systematically analyzed. This paper reviews 22 foodshed analyses completed in the USA and Canada between 2000 and 2013. The criteria used to evaluate the foodshed studies are authorship/type of publication, spatial extent, goals and questions, methods and data sources for assessing consumption and production, analysis of pathways from production to consumption and findings. Similarities and differences, along with strengths and weaknesses, are identified. Together, the foodshed studies indicate significant opportunity for food system relocalization across North America. Foodshed studies are a potentially powerful tool for policy analysis and planning. A future research agenda for foodshed studies is identified, including addressing data gaps and establishing more standardized models for evaluating production, consumption and pathways.

As the finishing touches go on this themed issue, evidence of widespread enthusiasm for urban farming is apparent in many developed countries. Farming in the city, commonly referred to as urban agriculture, has been put forth as a solution to multiple social problems, including the provision of new green spaces, control of runoff and provision of shade that offsets the heat of the concrete city. In cities with abundant vacant land and abandoned plots, urban agriculture promises a reduction of urban blight.

In 2014, Khan et al. presented evidence that soil exchangeable K (Exch-K) increases over time without addition of potassium (K) to the soil despite the removal of K in crops on a soil rich in montmorillonite and illite. The authors term this behavior ‘The potassium paradox’. From their review of the literature, the authors also report a lack of crop response to potassium chloride (KCl) fertilization. Close evaluation of these findings reveals that their observations can be interpreted and predicted using current knowledge of K in soil chemistry and its uptake by plants, and there is no paradox in K behavior in the soil–plant system. There is also no evidence of a detrimental effect of KCl on crop yield or quality. Their conclusion that the widely used Exch-K soil test is inadequate for managing K fertilization is discussed and some possible modifications to improve its performance are included. We believe that measurement of Exch-K is an essential and valuable tool and its use should be continued, along with improvements in recommending K fertilizer application.

Agriculture must face a number of very pressing environmental issues. We used the prototyping method to design three innovative cropping systems, each satisfying three ambitious goals simultaneously: (1) overcoming a major environmental constraint, which represents a major break regarding objectives to be reached in current cropping systems (differing between systems: a ban on all pesticides but with chemical nitrogen (N) fertilizer permitted; reducing fossil energy consumption by 50%; or decreasing greenhouse gas (GHG) emissions by 50%), (2) meeting a wide range of environmental criteria and (3) maximizing yields, given the major constraint and environmental targets. A fourth cropping system was designed, in which the environmental and yield targets were achieved with no major constraint (the productive high environmental performance cropping system (PHEP) system). The performances of these innovative cropping systems were compared to a conventional system in the Ile-de-France region. We used a three-step prototyping method: (1) new cropping systems were designed on the basis of scientific and expert knowledge, (2) these system prototypes were assessed with tools and a model (ex ante assessment) adjusted to the set of constraints and targets, with optimization by an iterative process until the criteria were satisfied and (3) evaluation in a long-term field experiment (ex post assessment), which is currently underway. We describe only the first two steps here, together with the results of the prototypes assessment with tools and a model. The pesticide, energy and GHG constraints were fulfilled. All these innovative systems satisfied environmental criteria in terms of nitrogen and phosphorus management, pesticide use, energy consumption and crop diversity. For the pesticide-free system, the soil organic matter indicator was lower than expected due to frequent plowing (every 2 years) and yields were 20–50% lower than for the PHEP system, depending on the crop considered. We focus our discussions on the design methodology and the availability of scientific knowledge and tools for projects of this type.

The living soil is the basis for crop production in organic agriculture. Biopores are voids in the soil which were formed by the activity of soil life. The first scientific studies on biopores were published in the 1870s–90s by Victor Hensen who stated that earthworms were opening channels to the subsoil and coating them with humus, thus creating a beneficial environment for root growth. His work was originally widely recognized, but then research on biopores was neglected for many decades and was only revitalized with the rise of ecological concerns in the 1960s. In recent times, biopores have attracted the attention of agronomists with a focus on organic agriculture. New visualization techniques, such as X-ray micro computed tomography, in-situ endoscopy and nuclear magnetic resonance imaging have been applied. Biopores contribute to air transport through the soil, increase water infiltration, reduce water runoff and soil erosion, serve as preferential pathways for root elongation and can facilitate the acquisition of water and nutrients from the subsoil. The relevance of biopores for nutrient acquisition can be pronounced particularly in organic production systems, where crops are more dependent on nutrient acquisition from the solid soil phase than under conditions of conventional agriculture. Organic land-use strategies should aim to increase number, stability and quality of biopores. The biopore density can be increased by the share of dicotyledons in the crop rotation and by cultivating perennial crops with taproot systems. Moreover, density and—in particular—the quality of biopores, e.g., the nutrient contents of pore walls, can be influenced by anecic earthworms which can be promoted by adapted tillage practices.

For many years, crop potassium (K) availability has been estimated by soil testing the plow layer for exchangeable K, in conjunction with potassium chloride fertilization widely promoted as an essential prerequisite for ensuring crop yield and quality. As rigorously documented in our paper, both components of chemical-based K management are seriously flawed by the lack of a scientific basis. Under the pretext of providing economic benefit for the producer and a healthy food supply for the public at large, the real purpose is to generate revenue for the fertilizer industry.

There is a need to design intensive cropping systems that can reap multiple benefits from annual forages including animal feed, soil fertility and weed control. Considering pea/oat (Pisum sativum cv. 40–10/Avena sativa cv. Legget) as a standard green manure, this study investigated the productivity, weed competitiveness, utilization and nitrogen (N) benefit from grazed and ungrazed green manures to spring wheat (Triticum aestivum cv. Waskada) and fall rye (Secale cereale cv. Hazlet). A set of 3-year experiments was carried out in Carman, Manitoba, Canada in 2009, and was repeated in 2010 and 2011. Green manures were grazed by 2–3 ewes and 2–5 lambs for 24 h (1111–1667 sheep days per ha). Averaged over experiments pea/oat mix, hairy vetch (Vicia villosa L.) and sweetclover (Melilotus officinalis cv. Norgold) above-ground dry matter (DM) production were 5036, 5032 and 4064 kg ha−1, respectively. Lentil (Lens culinaris cv. Indianhead), a mixture of seven species and soybean (Glycine max cv. Prudence) produced the least amount of DM over 3 years; 3589, 3551, 3174 kg ha−1, respectively. Pea/oat and hairy vetch were the most weed-competitive species and, averaged over 3 years, contained less than 15% weed DM. Utilization of green manures by grazing animals varied little among species across years and ranged from 28 to 86% for individual species and years. When combined across experiments grazing increased N availability to the wheat crop. The grazing effect was significant for wheat DM production, N uptake and grain N, but not significant for yield across experiments. Averaged over 3 years, wheat took up 107 kg N ha−1 from grazed plots versus 98 kg N ha−1 from ungrazed plots. A significant species×management interaction for total (wheat+fall rye) N uptake in 2009 indicated that increasing the proportion of legumes in the green manure increased N benefit from grazing. Fall rye productivity was not affected by grazing. We recommend pea/oat and hairy vetch as two green manure species to enhance the overall system performance to achieve high level of DM production, good weed competition, utilization by sheep and provision of N benefit to the following wheat and fall rye crops.

Urbandale Farm (Lansing, MI) has much in common with other urban agricultural projects throughout the US and especially those in the rust-belt cities of the Midwest. It raises food for an economically challenged neighborhood. It offers opportunities for local participation, education and job creation, and it is supported by diverse public and private institutions. By all official accounts, Urbandale Farm is good at what it does. Its acreage, production, income and entrepreneurial activities are all increasing, and it has become a poster child for urban agriculture throughout the city. However, despite its good work (or possibly because of it), Urbandale Farm, and urban agriculture more generally, may unwittingly be helping to rationalize the displacement and continued social and political inequity of urban neighbors rather than reinforcing greater place-making, neighborhood empowerment and sustainability. Using Urbandale Farm as a case in point, this paper critically explores how urban agriculture is being used by some scholars, activists, governmental offices and agencies to transform fragile neighborhoods. It questions some of the movement's underlying assumptions as well as some of its actual benefits and beneficiaries. The paper also offers suggestions—for the purpose of initiating a more nuanced conversation—on how urban agriculture can be reconfigured philosophically and practically to shed its neoliberal tendencies and contribute to a more structurally based social and political transformation.

Open-air crops are important in Spanish horticulture. The limited number of herbicide active ingredients in minor crops, the waste problem of polyethylene (PE) plastic mulch and the high prices of biodegradable plastics leave hand-weeding and mechanical weed control as the most viable weed control methods. Different tools have been tested in northern European countries but their performance remains unknown in the edaphoclimatic situation of southern Europe. The objective of this work was to test novel physical weed control methods on processing tomato in northeastern Spain compared with other effective control methods, i.e., plastic and paper mulches. A first sequence of field trials was established from 2005 to 2008 at Zaragoza (Spain) to select the best physical control methods out of flamer, torsion weeder, finger weeder, flex-tine harrow and brush hoe used alone or in combination. The best method was the brush hoe which was then compared from 2009 to 2011 with PE mulch, biodegradable plastic mulch and paper mulch. Flamer, flex-tine harrow, torsion weeder and finger weeder performed quite irregularly due to crusty soil conditions and needed additional tools or repeated treatments to increase weed control efficacy. The brush hoe performed best in this soil situation working at about 5 cm depth. Weed biomass reduction was higher than 80% in 6 out of 7 years and similar yield was obtained in the brushed plots compared to the yield obtained with PE, biodegradable plastic and paper mulch. The brush hoe is thus a suitable option for weed control in processing tomato while the other tools were too weak to control aggressive summer weeds in the tested conditions.

Underutilized crops tend to harbor high levels of genetic diversity, be maintained on-farm in small-scale farming systems and be relatively neglected by formal research and development strategies, including breeding programs. While high genetic variability allows these crops to adapt to marginal environments, inappropriate management practices and reductions in population sizes in individual farmers’ plots may lead to productivity loss and poor harvests. This situation further limits their cultivation and use, notwithstanding the potential these crops may hold for diversification of agricultural systems, food security and market development. Peru hosts a wealth of native agrobiodiversity, which includes many underutilized crops. To improve their performance and promote their continued conservation and use, a participatory breeding program was developed on five underutilized crops of the Peruvian highlands; the breeding approach, based on a combination of evolutionary and participatory methods, is designed to achieve a balance between yield improvement and maintenance of genetic diversity. Preliminary results in quinoa and amaranth are encouraging, fostering further engagement of farmers by increasing availability of quality seed for downstream uses. However, methodological, financial and institutional issues need to be addressed for the effort to be expanded and upscaled. This paper provides an overall description of the initiative as well as a discussion on early results obtained in quinoa and amaranth, highlighting those aspects that make this approach particularly relevant for minor crops and identifying the opportunities and challenges for the initiative to move forward.

Changes in methanogenic archaea were investigated in pilot-scale experiments during one- and two-stage mesophilic anaerobic digestion (AD) of food waste. Methane yields were 379.7±75.3 liters of methane per kg of volatile solids [L-CH4 (kg-VS)−1] added to the system, during one-stage operation, and 446±922 L-CH4 (kg-VS)−1 added during two-stage operation. Populations of methanogenic archaea were monitored quantitatively by targeting the functional gene for methyl-coenzyme-M reductase (mcrA) using real-time quantitative polymerase chain reaction techniques. During one-stage operation, mean mcrA gene concentrations were 2.48×109±2.7×109 copies ml−1. Two-stage operation yielded mean mcrA gene concentrations of 9.85×108±8.2×108 copies ml−1 in the fermentation and 1.76×1010±8.5×109 copies ml−1 in the methanogenesis reactors, respectively. Diversity of archaea in the methanogenic reactors was investigated by denaturing gradient gel electrophoresis targeting the V3 region of 16S rRNA of archaea. The Shannon index (H) was 2.98 for one-stage operation and 7.29 for two-stage operation, suggesting greater archaeal diversity in the two-stage AD. The fivefold increase in methanogenic archaea populations during the two-stage operation, as indicated by mcrA gene concentration, corresponded to an increase in methane production rates. While the diversity may also be related to the stability of the microbial bioprocesses and improved methane production rates, the correlation between diversity and production rates should be studied further.

The increasing demand for food from limited available land, in light of declining soil fertility and future threats of climate variability and change have increased the need for more sustainable crop management systems. Conservation agriculture (CA) is based on the three principles of minimum soil disturbance, surface crop residue retention and crop rotations, and is one of the available options. In Southern Africa, CA has been intensively promoted for more than a decade to combat declining soil fertility and to stabilize crop yields. The objective of this review is to summarize recent advances in knowledge about the benefits of CA and highlight constraints to its widespread adoption within Southern Africa. Research results from Southern Africa showed that CA generally increased water infiltration, reduced soil erosion and run-off, thereby increasing available soil moisture and deeper drainage. Physical, chemical and biological soil parameters were also improved under CA in the medium to long term. CA increased crop productivity and also reduced on-farm labor, especially when direct seeding techniques and herbicides were used. As with other cropping systems, CA has constraints at both the field and farm level. Challenges to adoption in Southern Africa include the retention of sufficient crop residues, crop rotations, weed control, pest and diseases, farmer perception and economic limitations, including poorly developed markets. It was concluded that CA is not a ‘one-size-fits-all’ solution and often needs significant adaptation and flexibility when implementing it across farming systems. However, CA may potentially reduce future soil fertility decline, the effects of seasonal dry-spells and may have a large impact on food security and farmers’ livelihoods if the challenges can be overcome.

In Sehoul, Morocco, the use of marginal land for agriculture became a necessity for the local population due to increased poverty and the occupation of the best land by new owners. Desertification poses an additional threat to agricultural production on marginal slopes, which are often stony and degraded. In a participatory process embedded in the EU DESIRE research project, potential sustainable land management measures were selected to address land degradation and desertification. Promising experiences with no-tillage practices elsewhere in Morocco had motivated the Moroccan government to promote conservation agriculture throughout the country. This combination of crop rotation, minimal soil disturbance and soil cover maintenance, however, had not yet been tested on sloping degraded land. Field trials of grazing enclosure combined with no or minimum tillage were conducted on the plots of two farmers, and trial results were analyzed based on stakeholders’ criteria. Results suggest that increased soil cover with barley residues improved rainwater use efficiency and yields only slightly, although soil water was generally enhanced. Soil moisture measurements revealed that no-tillage was favorable mainly at soil depths of 5 cm and in connection with low-rainfall events (<20 mm); under these circumstances, moisture content was generally higher under no-tillage than under conventional tillage. Moreover, stakeholder discussion confirmed that farmers in Sehoul remain primarily interested in animal husbandry and are reluctant to change the current grazing system. Implementation of conservation agriculture is thus challenged both by the degraded, sloping and stony nature of the land, and by the socio-economic circumstances in Sehoul.

Weed management is a major concern for organic farmers. Strategies and techniques used by organic farmers vary according to crops, soils, climate and other factors. Organic farmers in upstate New York experienced in weed management were interviewed about what weed–crop complexes they face, how they manage weeds, and what priorities they have for research. The interviews were complemented with an all-day focus group conducted with the farmers who were interviewed. All of the farmers interviewed relied heavily on cultural practices, such as crop rotation, fertility management, high-density planting, transplants and the use of cover crops. Mechanical practices were also important for the farmers interviewed. They emphasized selection of the appropriate tools for the situation and techniques for using tools effectively. Most of the farmers interviewed relied on intensive tillage to control perennial weeds. Differences in practices were notable among the farmers interviewed. Several farmers shared innovations both in practices and equipment modification. Farmers identified soil and nutrient management; tillage and cultivation tools and practices; natural herbicides; flame weeding and no-till systems without herbicides as research priorities. Some of the topics suggested for research have already received substantial research attention; identification of these topics by the farmers indicated a need to disseminate research findings through extension materials and demonstration of viable practices.

Pollinator declines and dependence on insect pollination, particularly in fruit and vegetable crops, creates a pressing need to understand growers' interactions with pollinators and factors affecting pollination strategies. At present, many growers are dependent on commercial honey bees (Apis mellifera), but diversified strategies may be necessary to secure adequate crop pollination in the future. As of yet, little social science research exists on pollination practices. This article presents the results of a survey of lowbush blueberry growers in Maine. The survey was part of a five-year pollination security study focusing on four fruit and vegetables crops in the Northeast US. The survey assesses grower perceptions of native pollinators' effectiveness and their perceptions of native pollinators' contribution to fruit set. Results indicate a widespread perception among growers of native pollinators' importance. While native pollinators are not effective enough to replace rented honey bees for three-quarters of the industry, they are broadly seen as an important form of insurance in poor weather when honey bees' effectiveness is reduced. The main obstacle to greater utilization of native pollinators found in this study was uncertainty over native pollinators' contribution to yield and the associated difficulty monitoring native pollinators' population size. Scientists and extension experts must work to reduce these obstacles before more widespread use of native pollinators will occur.

Despite the surge of interest in urban agriculture, there have been few studies that address the biophysical challenges and opportunities of food production in urban environments. This study aims to determine the relative influence of atmospheric pollutants and microclimatic factors on the physiological response and productivity of vegetable crops across an urban-to-rural latitudinal transect in the greater Chicago metropolitan region. Data collected at each of six sites include continuous measures of atmospheric pollutants and microclimatic factors, and biweekly measures of physiological response and yield of various vegetable crops and cultivars. Preliminary data collected in early 2013 suggest that there is substantial variability in environmental factors and crop yield across this urban-to-rural transect. Results of this study will provide a scientific basis for crop adaptation to the urban environment and establish practical crop and cultivar recommendations for urban and peri-urban farmers in the North Central US.

Farms producing similar products have become increasingly concentrated geographically over the past century in the United States (US). Due to the concentration of food production, a disruption in key production areas may reduce the availability of certain foods nationwide. For example, climate change poses such a threat, with projections of altered precipitation patterns, increased temperature and pest outbreaks, which may result in reduced crop yields and geographic shifts in crop adaptation. Analyses of the degree to which US regions can satisfy the food needs of their resident populations—a concept we refer to as regional self-reliance (RSR)—are therefore warranted. We focus on the Northeast region because of its high population density and declining agricultural landbase. Our objectives are to: (1) determine how agricultural land is used in the Northeast region; (2) determine the variety and amount of foods produced; and (3) analyze the relationship between food consumption and agricultural output. Annual (2001–2010) data on land area, yield and output of all crops and major livestock categories, as well as seafood landings, were catalogued. National annual (2001–2009) data on food availability were used as a proxy for estimates of food consumption, and these data were downscaled to a regional level and compared with regional production data in order to estimate RSR. In the Northeast region, approximately 65% of land in farms contributed directly to the food supply from 2001 to 2010, although this varied significantly across states. Just over one-half of all land in farms in the region was devoted to the production of livestock feed. The region produced >100 food crops annually from 2001 to 2009, and vegetables represented the majority of food crop production by weight. Chicken accounted for the largest weight of meat products produced. Compared to the Northeast region's share (~6%) of total land in farms in the nation, it accounted for disproportionately higher amounts of the national production of dairy (16%), eggs (13%), chicken (9%), lamb (7%) and vegetables (7%). However, the region accounted for ~22% of the national population and therefore produced a disproportionately low share of food on a per capita basis. RSR for plant-based foods was lowest for pulses (7%) and highest for vegetables (26%). There are four specific factors in the RSR in our analysis, each of which could result in substantial shifts (upward or downward) of the RSR in the future: land used for agriculture, crop (or animal) productivity, population and dietary preferences.

A recent increase in programs supporting the entry of organic farmers into direct market channels, such as farmers' markets and community-supported agriculture has occurred in the USA. In order to better implement these programs and to design better outreach and educational support activities for direct market farmers, understanding farmers’ perceptions of success in these marketing channels is valuable. To this goal, Wisconsin-certified organic vegetable farmers were surveyed in order to investigate the relationships between farm characteristics, marketing strategies, and farmer's perceptions of their profitability and quality of life. The data collected from this survey indicate that farmers selling into farmers' markets and through community-supported agriculture tend to be more likely to be dissatisfied with their profitability. Conversely, however, the survey data indicated that farmers selling into other markets, particularly wholesale markets and restaurants/institutions, are significantly more likely to be dissatisfied with their quality of life. Thus, it appears that farmers are making trade-offs with respect to entering markets that allow for greater financial rewards but may lead to a lower quality of life. These results point to the potential benefit of outreach efforts to assist farmers to increase their profitability in market channels that also provide a higher quality of life.