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EAGESTAD INRACover crops play an important role in agricultural sustainability. Unlike commodity cash crops, however, there has been relatively little cover crop breeding research and development. We conducted an online survey to evaluate: (a) the perspectives of organic and conventional farmers in the USA who use cover crops and (b) the specific cover crop traits that are important to farmers. We recruited participants from both organic and conventional agriculture networks and 69% of respondents reported that they farmed organic land. In addition to demographic data and information on management practices, we quantified farmer perspectives on four winter annual cover crops: (1) Austrian winter pea, (2) crimson clover, (3) hairy vetch and (4) cereal rye. Overall, respondents represented a wide range of states, farm sizes, plant hardiness zones and cash crops produced. Of the 417 full responses received, 87% of respondents reported that they used cover crops. The maximum amount farmers were willing to spend on cover crop seed varied by farmer type: 1% of conventional farmers versus 19% of organic farmers were willing to spend over US$185 ha−1 (US$75 acre−1). Organic and conventional farmers differed in terms of the reasons why they grew cover crops, with organic farmers placing greater value on the ecosystem services from cover crops. More organic (63%) than conventional (51%) farmers agreed that participatory breeding was important for cover crop variety development (P = 0.047). Both groups shared strong support for cover crop research and considered many of the same traits to be important for breeding. For the legume cover crops, nitrogen fixation was considered the most important trait, whereas winter hardiness, early vigor, biomass production and weed suppression were the most important traits for cereal rye. Our results illustrate common interests as well as differences in the perspectives between organic and conventional farmers on cover crops and can be used to inform nascent cover crop breeding efforts

Overwintered cover crops mechanically terminated into mulch can be a weed management tool for reduced-tillage organic agriculture. However, the impacts of management options for cover cropping are not well understood, including cover crop variety, termination timing and termination method. In a field experiment, conducted in 2012 and 2013 in Western Washington, we examined three grains, four vetches and one barley-vetch mix terminated with two mechanical methods and at two different times. We determined the influence of cover crop variety and termination time on cover crop biomass production and tissue nitrogen (N), effectiveness of cover crop termination, soil nitrate-N and percent weed cover. We also determined the influence of termination method on percent weed cover. Cover crop biomass ranged between 3 and 9 Mg ha − 1 and was not influenced by termination time; the greatest production was from three varieties of grain. Rye varieties were more effectively terminated with a roller-crimper than barley. Mean soil nitrate-N levels ranged from 1.9 to 18 mg kg − 1 and were the greatest with vetches. Post-termination weed cover was greater in 2013 than in 2012 and the cover crop variety influenced weed cover at the Late termination time only. Neither plant N concentration in the cover crop mulch nor soil nitrate influenced weed cover. The results of this study indicate that cover crop biomass and termination timing are important factors influencing weed cover and termination effectiveness in cover crop mulch.

Switchgrass is a promising bioenergy source that is perennial, productive, native to a broad geographic region, and can grow on marginal, nitrogen (N)-poor soils. Understanding N dynamics in switchgrass is critical to predicting productivity, conserving N, and optimizing the timing of harvest. We examined seasonal changes in N distribution in above-and belowground tissues in switchgrass to quantify N retranslocation rates. Above-and belowground biomass from three sites (two in PA and one in NE) were collected and analyzed for biomass growth and N concentrations at 30-day intervals from June through October. Total living plant mass ranged from 10.3± 2.4 standard error (SE) to 14.9±2.5 SE Mg ha −1. Belowground mass comprised 52-57 % of total mass. Blades had the highest N concentration during summer, ranging from 6 to 22 g kg −1 N.