Organic vegetable production in Florida is challenged by plant-parasitic nematodes and sandy soils subject to nitrogen (N) leaching. Researchers planted summer cover crops to enhance N cycling and soil health, suppress pest nematodes and weeds, and improve yield and quality of fall pepper, cucumber, or bok choy. Treatments included sunnhemp alone or with sorghum-sudangrass or millet and a four-way mix with sesbania versus no cover; and preplant organic fertilizer to meet crop N needs versus a half-rate preplant plus fertigation. A winter rye cover crop and spring chard followed vegetable harvest, then the same cover crop and fertility treatments were applied for a second season of fall vegetables. N transfer from cover crop to vegetable was tracked with 15N labeling; soils were analyzed for nutrients, carbon, nematodes, and microbial communities; and crop and weed biomass and yields were recorded.

Only 10-20% of cover crop N was recovered by the following vegetable crop. Cover crops suppressed summer weeds, reduced nutsedge in bok choy, and enhanced microbial-feeding nematodes but had little effect on crop yield, nutrient levels, or other soil health parameters. Applying all fertilizer pre-plant provided more carbon and boosted soil health parameters, available nutrient levels, and crop yields over the split application. However, split applications sometimes enhanced crop quality (soluble solids, acidity, vitamin C, antioxidants).