Soil Physical Properties, Nitrogen, and Crop Yield in Organic Vegetable Production Systems

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.