Cover Crops as Carbon Sources for Anaerobic Soil Disinfestation In a Vegetable Production System.

In a raised-bed plasticulture vegetable production system utilizing anaerobic soil disinfestation (ASD) in Florida field trials, pathogen, weed, and parasitic nematode control was equivalent to or better than the methyl bromide control. Molasses was used as the labile carbon source to stimulate microbially-driven anaerobic soil conditions. Warm-season cover crops can fill a summer-fallow niche in Florida vegetable production systems, which can have agronomic and environmental benefits. These cover crops can subsequently serve as on-farm carbon sources for ASD. To test whether cover crops could replace molasses in ASD, a greenhouse trial was conducted using field soil in which several warm-season legumes and grasses were grown and incorporated with or without composted broiler litter. Pots were then irrigated to fill porosity, allowed to drain, and covered with a clear plastic film to initiate a 3-week ASD treatment prior to planting tomatoes. Soil anaerobicity (Eh) was monitored during treatment and soil fertility was assessed throughout the experiment. In nearly all cases, ASD treatment utilizing cover crops resulted in cumulative Eh values that were equal to ASD treatment with molasses and greater than a fallow control without added carbon source. Immediately following ASD treatment, soil inorganic nitrogen in all treatments was primarily comprised of NH₄-N (85 to 97%) rather than NO₃-N, and was greatest in pots where a legume cover crop (sunn hemp or cowpea) was grown and/or composted litter applied. Throughout the study, germination of yellow nutsedge tubers introduced at treatment was highest in control pots without added carbon (75% tuber germination), lowest when molasses was applied (8% tuber germination), and intermediate from cover crop treatments (41 to 64% tuber germination). The number and weight of tomatoes harvested, and height and weight of tomato plants did not differ among ASD treatments.