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Managing soil quality is recognized as a cornerstone of maintaining crop production potential. Here we show that soil management that improves soil quality characteristics can also reduce year‐to‐year variation in yields. Thirteen years of data from the Maine Potato Ecosystem Project were used to investigate the long‐term effects of soil management, pest management, cultivar, and rotation in a factorial design on the yield and yield stability of potatoes grown in 2‐yr rotations. Potato (Solanum tuberosum L.) yields in the amended soil system (manure, compost, green manure, and supplemental fertilizer) were up to 55% higher than yields in the contrasting nonamended soil system (synthetic fertilizer) in all but 1 yr. Yield stability was also enhanced in the amended system compared with the nonamended system, as demonstrated by lower CVs of total and U.S. no. 1 potato tuber yield. Stability analysis indicated that yields in the amended system were less influenced by adverse growing conditions, particularly low rainfall. Total and U.S. no. 1 treatment yields in the poorest‐yielding year were 63 and 59% of maximum yields, respectively, in the amended system, compared with 45 and 46% in the nonamended system. Yields and yield stability were also influenced by pest management system and cultivar but not by rotation. These results indicate that management practices that improve soil quality can enhance potato yield stability by reducing the impact of adverse growing conditions.

Effective in-season weed management options are limited for organic cereal farmers. Two alternatives to current farmer practices are improving efficacy of physical weed control through use of interrow cultivation or increasing the competitive ability of the crop through elevated seeding rates and more uniform spatial planting patterns. It is unknown how these two methods affect yield, quality, and economic returns. Field experiments were conducted in the northeast United States to determine whether the yield gain from increased weed control from these contrasting weed management strategies resulted in increased net returns and how these different systems affected grain quality. Wheat was planted at two seeding rates (400 and 600 plants m−2), in three row spacings (11, 18, and 23 cm). A fourth crop arrangement that approaches a more uniform spatial distribution through a combination of drilling and broadcasting seed was included. For weed control, treatments received tine harrowing. Wheat sown in wide rows also received interrow cultivation. Each system was sown in the presence and absence of condiment mustard, which was sown as a surrogate weed. Increased seeding rate reduced weed density 64% compared to a crop-free check and 30% compared to regional farmers' practices of 18-cm rows and 400 plants m−2. Increased seeding rates lowered grain protein 5% compared to standard seeding rates. Wide rows, in combination with interrow cultivation, reduced weed density 62%, increased yield 16%, and net returns 19% compared to regional organic practices. Significant increases in grain N were limited to weed-free plots. While increased seeding rates improved weed suppression, the high input cost of organic seed make this an unsatisfactory alternative to interrow cultivation and current farmer practices, as yield would need to be. 15 t ha−1higher at elevated density to offset the extra cost of seed.

Cover crop performance depends largely on management factors that must be customized to particular farm situations and, therefore, is suited for on-farm research, with farmers involved in both management and evaluation. Cover crop sequences that were successful in a research station study were tested over a variety of soils and management strategies in collaboration withfarmers. The two-year cover crop sequences consisted of a short-season crop followed by a cover crop in year one and corn in year two. The cover crops themselves were evaluated by their agronomic and economic performance and their acceptance by farmers. Four cover crop systems (companionseeded red clover, sequentially seeded hairy vetch, sequentially seeded oat, and fallow) were compared for ground cover, above-ground biomass and above-ground nitrogen yield, subsequent corn grain yield, and N fertilizer replacement value (N-FRV). Cover crops were essential for erosion control following vegetable crops and tillage, but were not necessary following small grains. Companion-seeded red clover produced the most ground cover, yielded up to 133 kg N/ha, and had a higher average N-FRV than sequentially seeded hairy vetch on sandy loam soils, but was not preferred by farmers who harvested small grain straw as well as grain. Sequentially seeded hairy vetch gave excellent cover when no-till seeded, produced more than 125 kg N/ha in half the siteyears, and had a higher average N-FRV than companion-seeded red clover on silt loam soils. First-year N-FRV for the legume cover crops averaged 67 kg N/ha over both soil types. The participating farmers indicated that their decisions to adopt cover crops would be based primarily on their need for ground cover, and secondarily on the profitability of using cover crops as an N source. However, when valued solely as an N source for the next year's crop (and not for any potential long-term benefits), cover crops were not an economical alternative to N fertilizer. We suggest focusing future cover crop research and extension efforts on outreach to farmers growing crops that do not provide sufficient ground cover, such as short-season vegetable crops, and optimizing the cover crop system to maximize its erosion control benefits and increase its profitability over N fertilizer.

Ensuring adequate available N for grain protein development is a primary challenge for organic production of winter bread wheat (Triticum aestivum L.). Topdressing organic wheat in‐season may improve grain yield and quality. The objective of this study was to determine if supplemental N topdressing at key wheat developmental stages would improve organic hard red winter wheat yield and protein concentrations. Field experiments were conducted over 4 site‐years from 2009 to 2011 in Maine and Vermont, using the variety Harvard. Treatments were a factorial arrangement of two organic‐approved N sources (Chilean nitrate, CN, and dehydrated poultry litter, DPL) and three times of application (tillering, flag leaf, and boot stages). Plant N uptake, grain yield, and grain protein concentration were determined. Plant‐accumulated N was always higher in the CN treatments than in the DPL and manure‐only treatments. The CN topdress treatments yielded on average 11% more than the manure‐only treatment and 6% more than DPL treatments. Topdressing increased grain protein concentration in all cases, although none of the treatments reached the 120 g kg–1 milling standard, due in part to variety Harvard being a low‐protein, high‐yielding variety. Chilean nitrate was more effective at increasing grain protein levels than DPL, and for both N sources, later applications were more effective than earlier ones. Topdressing could be a cost‐effective strategy to boost grain protein levels for organic winter wheat production, but further work is needed to evaluate topdressing with higher protein varieties and identify additional rapidly‐available and economical organic approved N sources.