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

Abstract

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.