Assessing the Suitability of Biofumigation and Anaerobic Soil Disinfestation to Improve Vegetable Crop Performance in Michigan

Pressure to improve alternative pest management practices has risen in intensive cropping systems due to the loss of broad-spectrum fumigants. Adding to this is the variable and inconsistent efficacy of alternative management including biofumigation (BF) and anaerobic soil disinfestation (ASD). These practices were selected for evaluation based on amenability to environmental conditions of the upper Midwest. Biofumigation and ASD can be combined through the use of brassica cover crops and virtually impermeable films (VIF). Used in concert, these practices have the potential to confer the advantages realized from each system separately, including: improved nutrient cycling, soil warming, water retention, and disease suppression. The objective of this study was to evaluate the impact of BF and ASD on vegetable crop yield/quality while monitoring soil temperatures, nitrogen and CO₂ concentration. In 2012,  a field experiment was conducted at the Horticulture Teaching and Research Center (HTRC) in Holt, MI. Fifteen treatments were evaluated as a fully factorial combination of 5 cover crops [oilseed radish (Raphanus sativus ‘Defender’), Oriental mustard (Brassica juncea ‘Pacific Gold’), yellow mustard (Sinapis alba ‘Ida Gold’), oat (Avena sativa ‘Excel’) and a bare ground control] with 3 mulching practices applied following cover crop incorporation (standard black plastic film (BP), VIF, and no mulch (NM). Prior to incorporation, the cover crops were evaluated for dry biomass and nutrient content. Following mulch application, soil temperature, CO₂ concentrations, and soil nitrogen were monitored. Fresh-market tomato (Lycopersicon lycopersicum cv. ‘Big Beef’) was then transplanted, grown, and evaluated for plant biomass and crop yield/quality. Cover crop (and residual weed) biomass at incorporation was 1939, 1229, 1210, 2030, and 651 kg/ha for R. sativus, B. juncea, S. alba, and A. sativa and bareground treatments, respectively. No differences were observed in yields among cover crop treatments, possibly due to lower than normal biomass accumulation. During ASD, soil nitrate and ammonium were higher under plastic treatments while CO₂ levels were highest under VIF and lowest under NM. Tomato fruit yield and shoot biomass was significantly lower on BP and VIF treatments compared with NM.  Mulch treatments provided favorable soil temperatures early in the growing season, however, unusually high mid-season temperatures led to root-zone temperatures above optimal for tomato growth.  Our initial results suggest that under low disease pressures and high temperatures, combining practices may result in lower yields