Many consumers are trying to reduce their food's environmental impact by purchasing more locally sourced food. One choice for local food is Community Supported Agriculture (CSA), in which farmers provide a share of produce on a regular basis to pre-paying farm members. The number of CSAs in the USA has grown from two in the mid-1980s to perhaps as many as 12,617 according to the latest US census of agriculture (2014). We use a case study approach to investigate the greenhouse gas (GHG) emissions associated with five CSA operations in the Sacramento Valley of California. By understanding the GHG emissions of CSAs and the practices that might be improved, we hope to support innovative strategies to reduce GHG emissions in these agricultural production systems. Input, production and distribution data were collected from each farm and reported in CO2e emissions for 1 kg CSA produce at the pickup location. Results show large variation in total emissions, ranging from 1.72 to 6.69 kg CO2e kg−1 of produce with an average of 3.94 kg CO2e kg−1 produce. The largest source of emissions was electricity, contributing over 70% of total CO2e emissions on average. Based on our findings, despite the seemingly similarities between these operations in terms of production site, acreage, customers and production practices, there is still a large amount of variability with regard to total GHG. Thus we argue coming up with a standardized production function for diversified production and deriving GHGs or calculating average total emissions overlooks the heterogeneity of the system. Food systems can never be reduced to a simple binary of local is better and conventional is worse, or its inverse local is worse and conventional is better, because of the complexities of the production and distribution systems and their relationship to GHG emissions. Yet, we can say that localized production systems that are low in electricity use (or use renewable energy sources) and use efficiently-produced compost use have lower GHG emissions than those that do not.

Benefits of reduced tillage and diverse crop rotations include reversing soil C loss, and improving soil quality and function. However, adoption of these strategies is lagging, particularly in the Upper Midwest, due to a perception that reduced tillage lowers crop yields. Therefore, an 8-year comparison of these conservation systems with a conventional, tilled, 2-year rotation system was conducted to evaluate effects on yields, system productivity (measured with potential gross returns) and weed seed densities. This study compared conventional moldboard plow + chisel till (CT) to reduced strip-tillage + no-tillage (ST), each with a 2-year (2y) or 4-year (4y) crop rotation, abbreviated as CT-2y, CT-4y, ST-2y and ST-4y. The 2y rotation was corn (Zea mays L.) and soybean (Glycine max [L.] Merr.); the 4y rotation was corn, soybean, spring wheat (Triticum aestivum L.) underseeded with alfalfa (Medicago sativa L.) and alfalfa. Only corn grain was significantly influenced by tillage strategy; CT systems yielded more than ST systems, regardless of rotation. Soybean grain yields were similar among CT-2y, CT-4y, ST-4y and lowest in the ST-2y. Yields of wheat and alfalfa were the same under both tillage strategies. Weed seed densities were higher in wheat and alfalfa, followed by corn then soybean, but were not influenced by tillage or rotation, nor universally negatively correlated to yield. Due to greater corn yields, overall system productivity was highest in CT-2y, the same between CT-4y and ST-2y, and lowest in ST-4y. Within years, productivity of CT-2y was different from only one other system at a time in 3 of 8 years and had the same productivity as all systems in another 3 of 8 years. Additionally, the similarity of productivity among three of four systems in 6 of 8 years indicated reduced tillage and diverse rotations have potential for adoption. Results support the need for research on a rotational tillage strategy, i.e., moldboard plowing before corn, to improve overall productivity if using ST before soybean, wheat and alfalfa.

Hulless oats are of interest as an alternative to corn and wheat in organic poultry diets because they offer potential to enhance agrobiodiversity and produce locally grown feeds both within and outside of corn-growing regions. Hulless oats are easily certified GM-free and have demonstrated nutritional value for poultry. A feeding study was carried out to examine: (i) the effects of substituting corn, wheat or a fraction of each with hulless oats in organic layer diets, and (ii) the importance of oat variety in feed performance. Productivity and economic implications in the context of current organic markets were explored. Experimental diets included an oat-free control, Oat + corn, Oat + wheat and Oat + corn + wheat, each of which was formulated with three hulless oat varieties, AC Gwen, Paul and Streaker. All but the control diet included oats at 200 g kg−1. Three hundred Hy-Line Brown hens were individually caged and allocated to diets in groups of 10 in a completely randomized design with three replicates per diet. Experimental diets were fed between 24 and 32 weeks of age during which time hen health, egg production and egg quality indicators were monitored. Results indicated that hulless oats had no negative effects on hen health and productivity. On the basis of current organic feed ingredient prices and an estimated cost of USD 533 mt−1 for production of oats in the study region, oat containing diets were more expensive than the oat-free control. In an evaluation of revenue based on current market prices for organic eggs, the additional cost was completely offset by larger egg sizes of hens on oat containing diets. There were no major differences associated with oat variety.

The need to ensure food safety has been recognized in China and the ‘Green Food’ system is used to restrict the use of chemical fertilizers and pesticides in its certified products. There has been limited study of the environmental impacts associated with the production of green food certified (GFC) products in China. In this study, life cycle assessment was used to evaluate environmental impacts of GFC cucumber cultivated under a greenhouse system in the suburbs of Beijing relative to conventional cultivation (CON), with the aim of identifying the key areas of potential environmental burden in cucumber cultivation. Eight environmental impact categories are considered, including global warming potential, energy depletion (ED), water depletion, acidification potential, aquatic eutrophication (AEU), human toxicity (HT), aquatic eco-toxicity (AET) and soil eco-toxicity (SET). Results showed that the environmental index of the GFC cucumber system was higher than that of the CON cucumber system. SET, EU and ED were identified as the main potential environmental impacts in cucumber systems, largely caused by fertilizer use on the farm. The potentials of HT and AET in GFC cucumber were lower than those in the CON system, mainly due to the reduced use of chemical pesticides. The agricultural input of plastics was the main contributor to energy depletion in both cucumber cultivation systems. Potential approaches to mitigate the environmental impacts of cucumber cultivation include increasing the fertilizer use efficiency, avoiding use of animal manure with high heavy metal content and recycling of plastics under the GFC cultivation system.

Better management of synthetic nitrogen (N) fertilizers in conventional agricultural systems laid the foundation for feeding the increasing world's population since the Green Revolution. However, excessive reliance on inorganic fertilizer has resulted in environmental degradation issues. Difficulties in soil nutrition management in organic cropping systems often results in lower and variable yields, also raising questions of sustainability. Improving nitrogen use efficiency (NUE) is thus of key importance to overcome environmental concerns in conventional systems and production limitations in organic systems. The differences in the two farming systems have impacts on crop traits and N cycles, making it difficult to enhance NUE with a single strategy. Different approaches need to be adopted to improve NUE in each system. Extensive efforts have been made to better understand mechanisms to potentially improve NUE in cereal crops under both systems. This review suggests that NUE may be improved through a combination of management practices and breeding strategies specific to the management system. Diversified crop rotations with legumes are effective practices to optimize the N cycle in both conventional and organic systems. Best Management Practices coupled with nitrification inhibitors, controlled release products and split-application practices can reduce N loss in conventional systems. In organic systems, we need to take advantage of available N sources and adapt practices such as no-tillage, cover crops, and catch crops. Utilization of beneficial soil microorganisms is fundamental to optimizing availability of soil N. Estimation of soil organic matter mineralization using prediction models may be useful to enhance NUE if models are calibrated for target environments. Cereal crops are often bred under optimum N conditions and may not perform well under low N conditions. Thus, breeders can integrate genetic and phenotypic information to develop cultivars adapted to specific environments and cultivation practices. The proper choice and integration of strategies can synchronize N demand and supply within a system, resulting in reduced risk of N loss while improving NUE in both conventional and organic systems.

Concerns are growing over the ability of the modern food system to simultaneously achieve food security and environmental sustainability in the face of global change. Yet, the dominant tendency within university settings to conceptualize and address diverse food system challenges as separate, disconnected issues is a key barrier to food system transformation. To address this fragmented approach, educators in North American institutes of higher education have begun new degree programs, specializations and certificates related to food systems. These programs, which we term sustainable food system education (SFSE) programs, have a common goal: to support post-secondary students across a range of disciplines in developing the knowledge, skills and dispositions to effectively address complex challenges in the food system. Graduates of these programs will be able to engage in collective action towards transforming the food system. As educators participating in flagship SFSE programs, we identify common pedagogical themes evident in SFSE programs, including our own. We then propose a signature pedagogy (SP) for sustainable food systems education. Signature pedagogies are conceptual models that identify the primary elements by which professional education in a specific field is designed, structured and implemented. On the basis of our analysis of SFSE programs, we identified systems thinking, multi-, inter- and trans-disciplinarity, use of experiential learning approaches and participation in collective action projects as central themes within a SFSE SP. By making these themes and their function explicit within a pedagogical framework, we seek to spur critical and creative thought regarding challenges of professional education in the field of sustainable food systems. Scholars and practitioners are encouraged to review, critique and implement our framework to advance the dialogue on SFSE theory and practice.

Agricultural expansion contributes to the degradation of biodiverse ecosystems and the services these systems provide. Expansion of urban and peri-urban agriculture (UPA), on the other hand, may hold promise to both expand the portfolio of ecosystem services (ES) available in built environments, where ES are typically low and to reduce pressure to convert sensitive non-urban, non-agricultural ecosystems to agriculture. However, few data are available to support these hypotheses. Here we review and summarize the research conducted on UPA from 320 peer-reviewed papers published between 2000 and 2014. Specifically, we explored the availability of data regarding UPA's impact on ES and disservices. We also assessed the literature for evidence that UPA can contribute to land sparing. We find that the growth in UPA research over this time period points to the emerging recognition of the potential role that UPA systems play in food production worldwide. However, few studies (n = 15) place UPA in the context of ES, and no studies in our review explicitly quantify the land sparing potential of UPA. Additionally, while few studies (n = 19) quantify production potential of UPA, data that are necessary to accurately quantify the role these systems can play in land sparing, our rough estimates suggest that agricultural extensification into the world's urban environments via UPA could spare an area approximately twice the size of the US state of Massachusetts. Expanding future UPA research to include quantification of ES and functions would shed light on the ecological tradeoffs associated with agricultural production in the built environment. As food demand increases and urban populations continue to grow, it will be critical to better understand the role urban environments can play in global agricultural production and ecosystem preservation.