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.

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Organic vegetable crops require intensive management, posing challenges for managing N and maintaining organic matter. This experiment was designed to evaluate effects of cropping systems, amendment N sources, and tillage types on soil organic matter, nutrients, physical properties, N availability, and crop yield in organic vegetable production. The experiment was established in 2003 in Puyallup, WA, with cropping system as main plots (fall‐planted cereal–legume cover crop, relay‐planted legume cover crop, and low‐input short‐term grazed pasture), tillage type as split plots (conventional and rotary spader), and amendment as the second split (broiler litter– low C input, and mixed compost–high C input). Vegetable crops were rotated across beds within plots. Yield, available N, soil C, nutrients, bulk density, infiltration, and compaction were measured. Soil C was greater with mixed compost (24 g kg−1) than broiler litter (18 g kg−1), and lower in the low‐input pasture than the cover crop systems. Soil physical properties were most affected by the presence or absence of tillage, and compaction was less with spader tillage. Short‐term N availability was similar between amendments and between fall and relay cover crops. Long‐term N availability was greater with mixed compost compared with broiler litter. Significant differences in crop yield occurred in 12 of 26 harvests. Yield differences among cropping systems were most common, with N availability and competition likely causes. Amendment and tillage affected yield in only 3 of 26 harvests. These results provide farmers with options for organic vegetable production in the maritime Pacific Northwest. Broiler litter and mixed compost soil amendments produced similar vegetable yields. Broiler litter maintained soil C, whereas mixed compost increased soil C. Cover crops did not increase soil C. Nitrogen supply from the fall and relay cover crops were similar. Spader tillage reduced soil compaction compared with conventional tillage.