2018 ASHS Annual Conference

Anaerobic soil disinfestation (ASD), based upon supplying a labile carbon (C) source, tarping, and watering the soil to field capacity to achieve soil anaerobic conditions, has shown to be a promising strategy for controlling soil-borne plant pathogens and parasitic nematodes and to improve vegetable production. To test the effectiveness of a summer leguminous cover crop, sunn hemp, as a potential carbon source for ASD, a pilot study of organic pac choi production was conducted at the University of Florida Plant Science Research and Education Unit in Citra, FL during the fall 2017 season. Summer-planted sunn hemp was used as the carbon source for ASD treatment using two approaches: terminated and incorporated into the soil in situ (SH_I) vs. aboveground biomass harvested and transported off site for soil incorporation (SH_T). In addition, composted poultry litter (CPL) was incorporated with sunn hemp (SH+CPL) or without (SH) in the ASD treatments. A standard ASD treatment with molasses and CPL and an untreated control (UTC) were also included. The raised beds for pac choi planting were irrigated to saturation and covered with black totally impermeable film (TIF) to initiate a 3-week ASD treatment beginning Oct. 19, 2017. Twenty-four-day-old pac choi seedlings were transplanted on Nov. 13 and the mature heads were harvested 38 days after planting. Two field trials each using a completely randomized design with four replications were conducted simultaneously. In trial 1, SH_I+CPL, SH_T, SH_T+CPL, and the standard ASD had significantly greater yields than SH_I and UTC. In trial 2, treatments that utilized CPL resulted in higher yields than treatments that included only the cover crop and UTC. Interestingly, yellow nutsedge, the predominant weed in the beds and planting holes, grew in significantly higher numbers in SH_I+CPL compared to UTC and other treatments in trial 1, while both SH_I and SH_I+CPL had significantly greater nutsedge counts than UTC and other treatments in trial 2. The crop yield discrepancy between the two trials might have resulted from the different levels of weed pressure present in the field. Nevertheless, the potential of using sunn hemp biomass as a carbon source for ASD treatment deserves more in-depth studies, together with analysis of the contribution of sunn hemp to soil fertility and quality