Cover Crop, Mulch, and Organic No-till Effects on Organic Vegetable Production Systems

This project addresses critical stakeholder needs for improving organic vegetable farming practices to optimize pest management, crop quality, and profitability, while enhancing soil quality. Treatments include three tillage comparisons: tilled followed by straw mulch, tilled without straw mulch, and organic no-till; and two organic fertility treatments: composted animal manure alone and with cover crops. In 2013, experiments were continued in Iowa and Florida across two contrasting soil types and climatic conditions using vegetable rotations appropriate for the region. A modified experimental design was used at the Florida site to include a plastic mulch vs. straw mulch comparison. Fall cover crops were planted in Iowa at a rate of 25 lb/acre hairy vetch and 90 lb/acre  rye, while in Florida, only cereal rye was used. Cover crops were disked under or terminated with a roller/crimper. Because of extensive spring rains in 2013, cover crops were not disked until June 8 and not rolled until June 20, leading to a planting date three weeks behind schedule. Compost was applied at a rate of 100 lb N/acre and organic fertilizer side-dressed after vegetable crop establishment at 50 lb N/acre. In Iowa, organic crops performed similarly to the 2012 drought year, with tilled plots providing higher sweet corn yields, at 3,595 lb/acre, than organic no-tillage plots, at 1,554 lb/acre. While the tilled crops were more productive, the mulched and no-till tomatoes had higher quality fruit. In the Florida trial, the total marketable fruit number and weight of summer squash were significantly higher in the reduced till plots as compared with other treatments.  Soil quality comparisons show greater soil carbon sequestration with cover crops and compost. Soil quality at the Florida site in January 2013 found total soil N, particulate organic matter C, extractable K and Mg, and electrical conductivity significantly lower in the tilled soils. Bulk density and extractable P were significantly greater with cover crops. Mulching and cover crops resulted in more extractable P and Mg and higher electrical conductivity. Overall, soil quality data in 2013 for these relatively un-structured Florida soils showed enhanced storage of soil N and biologically active soil C, and higher concentrations of plant nutrients in the no-till organic vegetable rotations compared to the tilled rotations.