Cover crop mulch-based no-tillage (MBNT) production is emerging as an innovative alternative production practice in organic farming (OF) to reduce intensive soil tillage. Although European organic farmers are motivated to implement MBNT to improve soil fertility and achieve further management benefits (e.g., labor and costs savings), low MBNT practice is reported in Europe. Thus, this paper aims to understand the challenges of both farmers and researchers limiting the further adoption of MBNT in organic farming in temperate climates. The primary no-tillage (NT) practices of organic European farmers and findings of organic MBNT studies conducted in Europe are reviewed, focusing on living or mulch cover crop-based NT (LBNT or MBNT) for arable crop production. Major conclusions drawn from this review indicate consistent weed control and an establishment of best practices for cover crop management as the two main overarching challenges limiting adoption. In view of substantial gaps of knowledge on these issues, additional research should focus on cover crop selection and management (species, date of sowing) to increase cover crop biomass, particularly in warmer climates. Lastly, further research is needed to optimize cover crop termination to prevent competition for water and nutrients with cash crops, particularly in wetter northern conditions which promote vigorous cover crop growth.

Sustainable cropping systems that balance agricultural productivity and ecological integrity are urgently needed. Overreliance on soil tillage and herbicides to manage weeds has resulted in a number of major environmental problems including soil erosion and degradation, biodiversity loss, and water quality impairment. Combining organic farming and conservation agriculture is a viable alternative to address these challenges. In particular, mulch-based no tillage systems can be used to reduce tillage in organic production, improving soil quality while decreasing labor and fuel requirements. This technique involves planting cash crops directly into terminated cover crops that remain on soil surface and serve as mulch to prevent weeds establishment and protect soil from erosion. Despite potential benefits, adoption of organic mulch-based no tillage is limited due to challenges with cover crop termination, weed suppression, and yields. Here, we (i) review international research on organic mulch-based no tillage systems (soybean and maize), (ii) identify production issues that limit the success of this technique, and (iii) outline research priorities. As result, organic mulch-based no tillage is knowledge intensive and requires advanced planning and careful management of the cover crop. Primary challenges include timely cover crop establishment and termination, nutrient management, reduced soil temperature and moisture at planting, and achieving adequate seed-to-soil contact when planting into thick mulch on soil surface. Long-term research is needed to better understand the effects of this technique production on soil health and on the broader environmental and economic impacts. To increase adoption of organic mulch-based no tillage, future research should focus on (i) screening species and cultivars to identify cover crop and crop combinations that optimize cropping system performance and (ii) developing equipment for improving cover crop termination and seed placement. Research conducted in partnership with farmers will be valuable for developing guidelines and increasing adoption of this technique. Keywords Direct seeding. Organic farming. Residue. Roller-crimper. Weed management Contents 1. Introduction 2. Scope of international research on mulch no tillage in organic farming 3. How can cover crop and cash crop management optimize organic mulch-based no tillage success? 4. Research agenda for the future 5. Conclusion References

Abstract:The organic industry continues to expand in the United States (U.S.), with 14,093 organic farms in 2014. The upper Midwestern U.S. has emerged as a hub for organic row crop production; however, the management of these organic row crop hectares heavily relies on tillage and cultivation for weed control. Faced with the soil quality challenges related to these practices, and cognizant of the benefits of conventional no-till practices, organic farmers have shown significant interest in the development of Cover Crop-Based Reduced Tillage (CCBRT) techniques to lessen soil disturbance while achieving successful weed management. To serve this farmer interest, significant research efforts have been conducted in the upper Midwestern U.S., focused on systems-based practices to ensure adequate suppression of weeds, through a combination of agronomic and cover crop species and variety selection. Within this review article, we discuss the agronomic successes that have been achieved in CCBRT using a combination of cereal rye and soybeans, resulting in consistent suppression of weeds while providing fuel and labor savings for farmers, as well as the continued challenges that have persisted with its implementation. Continued investment in research focused on cover crop breeding and management, optimization of CCBRT equipment and fertility management, and a greater understanding of rotation effects will contribute to the further expansion of this technique across organic farms.

The influence of tillage, carbon (C) and nitrogen (N) inputs and perennialization on labile fractions of soil organic matter (SOM) has been widely investigated, but research on the temporal and depth variation of labile C and N fractions in long‐term agroecosystems representative of the US Corn Belt is lacking. In this study, labile soil fractions as influenced by different agriculture management approaches common in the north‐central United States were characterized through measurements of potentially mineralizable N (PMN), mineralizable C (C‐min), and permanganate oxidizable C (POXC), which are known indicators of the biologically active pool of SOM. Soils were sampled five times in six different cropping systems at the Wisconsin Integrated Cropping Systems Trial: three annual cropping systems (continuous corn, strip‐till corn–soybean, organic grain) and three forage cropping systems (conventional forage, organic forage, grazed pasture). Across all sampling dates (May–September) and soil depth (0–15 and 15–30 cm), forage‐based cropping systems generally had greater PMN, C‐min, and POXC, with C‐min and PMN expressing the largest differences between forage and grain‐based cropping systems. Labile soil C and N fractions across cropping systems were typically greatest in July or August and were ∼50% greater in the top 0 to 15 cm of soil than the 15 to 30 cm. These results suggest sampling timing and depth for PMN, POXC, and C‐min need to be standardized to optimize their use as soil health indicators and that shifts in the system toward perenniality will be required to increase labile C and N fractions on the highly fertile Mollisols of the US Corn Belt.

The discovery of acrylamide in processed potato products has brought increased interest in the controlling Maillard reaction precursors (reducing sugars and amino acids) in potato tubers. Because of their effects on nonenzymatic browning of fried potato products, reducing sugars and amino acids have been the focus of many potato research and breeding programs. This study focused on changes in sugars and amino acids in diploid potatoes selected for their storage qualities and their effect on acrylamide formation in the fried product. In addition, a second study was performed using cultivated lines that evaluated the effect of nitrogen fertilization on amino acid levels in tubers. Glucose, fructose, sucrose, and asparagine concentrations in tubers increased upon storage at 2 degrees C. Glucose and fructose concentrations in the tubers were significantly and positively correlated with subsequent acrylamide formation in the products. Tuber sucrose and asparagine concentrations did not have an effect on acrylamide levels. Acrylamide levels in the products were significantly reduced if tubers were preconditioned before being placed in storage at 2 degrees C. Higher rates of nitrogen fertilization resulted in increased amino acid concentrations in the tubers.

Dual-use cover/green manure (CGM) crops and animal manure are used to supply nitrogen (N) and phosphorus (P) to organically grown field crops. A comprehensive review of previous research was conducted to identify how CGM crops and animal manure have been used to meet N and P needs of organic field crops, and to identify knowledge gaps to direct future research efforts. Results indicate that: (a) CGM crops are used to provide N to subsequent cash crops in rotations; (b) CGM-supplied N generally can meet field crop needs in warm, humid regions but is insufficient for organic grain crops grown in cool and sub-humid regions; (c) adoption of conservation tillage practices can create or exacerbate N deficiencies; (d) excess N and P can result where animal manures are accessible if application rates are not carefully managed; and (e) integrating animal grazing into organic field crop systems has potential benefits but is generally not practiced. Work is needed to better understand the mechanisms governing the release of N by CGM crops to subsequent cash crops, and the legacy effects of animal manure applications in cool and sub-humid regions. The benefits and synergies that can occur by combining targeted animal grazing and CGMs on soil N, P, and other nutrients should be investigated. Improved communication and networking among researchers can aid efforts to solve soil fertility challenges faced by organic farmers when growing field crops in North America and elsewhere.

Organic farmers have identified soil fertility and weed management as the two highest research priority areas. No review exists of research on soil nutrient management in organic field crop systems. We conducted a comprehensive review to identify the principles and factors governing nutrient management, knowledge gaps, and future research needs in organic grain and other field crop systems in Canada and the United States. We compared results from research conducted in different climates, soils, and crop rotational sequences. Results indicate that (i) dual‐use cover/green manure crops and/or animal manure are the most common sources of plant available N and other nutrients in organic field crop systems; (ii) soil nutrient deficiencies can develop through sole reliance on cover/green manure crops; (iii) dependence on animal manure can lead to N and P excesses; (iv) conventional soil testing procedures may not accurately predict crop nutrient needs; (v) greater knowledge of microbial processes governing nutrient cycling is needed; and (vi) better understanding of the impact of weeds on soil fertility may create weed and nutrient management synergies. Knowledge gaps include a lack in understanding of how the soil and plant biomes influence nutrient‐use efficiency and how crop diversity and rotations impact soil fertility, sustainability, and resilience in organic field crop systems. Likewise, interactions between weeds, crops, soil fertility, and weed management strategies are poorly understood. Core Ideas Soil, climate, fertility sources, and land use impact organic nutrient management strategies. Cover/green manure crops and animal manures are used to maintain soil fertility on organic farms. Conventional soil testing may not be ideally suited to organic systems. Tracking soil nutrient temporal changes can improve comprehensive nutrient management plans. More research of how weeds and soil microbial community structure/function impact nutrient cycling and crop production is needed.

Irrigated vegetable production dominates the landscape of the Central Sands region of Wisconsin, where sandy soil limits nutrient and water retention. Sweet corn (Zea mays L. var. rugosa) was managed organically in 2011 and 2012 growing seasons to evaluate effects of organic N input and weed management with respect to sweet corn yield and soil N content. The first treatment factor was early season manure, including spring‐seeded field pea (Pisum sativum L.) incorporated as a green manure cover crop, pelletized poultry manure, and no manure. The second treatment factor was weed management intensity. The last factor was varying N application rate, split applied as feather meal during the growing season. There was a positive yield response to feather meal in both years with yields reaching 18.6 and 21.5 Mg ha−1 in 2011 and 2012, respectively, with 224 and 112 kg N ha−1 feather meal application, respectively. Early season manure treatments did not clearly affect yields despite 90 kg N ha−1 applied as both manure types in 2012, and lower rates of 33 and 75 kg N ha−1 applied in 2011 as field pea and poultry manure, respectively. These results underscore the well‐known potential for rapid nutrient loss on coarse soil and management challenges associated with asynchrony between organic N release and crop uptake. Weed management contributed to an interaction effect on yield, with early tillage potentially controlling weeds in both treatments. This study demonstrated benefits of in‐season organic amendment use, though limited potential for early season application on loamy sand.Core Ideas Feather meal is a viable organic nitrogen fertilizer for sweet corn on loamy sand. Pre‐plant application of manures did not reduce optimum in‐season N application rate. Irrigated organic sweet corn can produce yields comparable to those of conventional methods.