The 2012 ASHS Annual Conference

Anaerobic soil disinfestation (ASD) is a non-chemical, pre-plant soil treatment developed to control soilborne plant pathogens, plant-parasitic nematodes, and weed populations in specialty crop production systems. Soil treatment by ASD involves the incorporation of a labile carbon source, tarping with plastic, and irrigation of the topsoil to saturation (~ 5 cm irrigation) in order to create conditions conducive to anaerobic decomposition of the added carbon source. A field study was implemented in March 2011 in Knoxville, TN to evaluate potential carbon sources for ASD prior to production of fresh-market tomato (Solanum lycopersicum cv. Red Defender) and bell pepper (Capsicum annum cv. Red Knight X3R). Carbon sources included: 1) dried molasses (5.6 Mg·ha^-1); 2) cereal rye (Secale cereale)  cover crop residue (9.3 Mg·ha^-1); 3) cereal rye residue supplemented with dried molasses (1.1 Mg·ha^-1); 4) mixture of mustard (Brassica juncea and Sinapsis alba) and arugula (Eruca sativa) cover crop residue (5.8 Mg·ha^-1);  5) mixture of mustard/arugula cover crop residue supplemented with dried molasses (1.1 Mg·ha^-1); 6) mustard seed meal (2.2 Mg·ha^-1, biofumigant control); and 7) an untreated control. Plots (22.3 m²) were arranged in a randomized complete block design. Following incorporation of amendments and cover crops, raised beds were formed in the center of each plot and irrigated. Treatment continued for a 3-week period, during which time soil redox potential (a measure of anaerobic activity shown to be correlated with pathogen mortality during ASD treatment), soil temperature, and soil moisture were continuously monitored. Following ASD treatment, tomato and bell pepper were transplanted on half of each plot and treatment impacts on vegetable yield, plant nutrition, soil fertility, weed control, and plant disease evaluated. Accumulation of anaerobic conditions was highest (P < 0.05) in both treatments which included cereal rye residue as a carbon source and lowest in the untreated and biofumigant controls.  Weed populations were low throughout the study, and all treatments were generally similar to the controls in numbers of monocot and dicot weeds.  Marketable yields of both tomato and bell pepper did not differ among treatments suggesting that pathogen and weed pressure were not high enough at this site to adequately evaluate ASD treatment.