On-farm Research Using Soil Amendments for Soil Quality and Disease Suppression in Organic Vegetable Systems

Demand for organic vegetables continues to rise yet growers struggle to effectively manage nutrients and plant disease. Soil microbes regulate nutrient cycling and help plants resist pathogens through intimate associations with plant roots. The composition and activity of these communities is influenced by organic fertility amendments as well as site-specific soil and environmental conditions. The objectives of this research project are to: 1) identify soil amendments that improve soil quality and increase crop productivity on organic vegetable farms, 2) identify how resident microbial communities interact with soil amendments to regulate nutrient cycling and suppress plant pathogens, and 3) demonstrate and increase the practice of on-farm research. Growers and researchers participated in a workshop in spring 2013 to develop a research plan. Annually repeated applications of four organic soil amendments (pelletized chicken manure, animal byproducts, mixture of animal and plant byproducts, and vermicompost) are being evaluated on three farms in Indiana and Ohio over a period of three years using a randomized complete block design with four replicates. In 2013, cabbage was grown in the plots and evaluated for stand establishment, disease incidence and severity, leaf nutrients, yield and size. Impacts of treatments on soil quality were evaluated using laboratory assays to determine nutrient availability, labile carbon, microbial activity, and microbial community diversity; and pathogen bioassays are on-going. On-farm assays were used to determine water infiltration and soil respiration. An organic soil management workshop and accompanying field day were held at one of the farms in July 2013 to discuss soil quality and on-farm research. Results from the first year show large differences in soil quality between the three farms, but little effect of soil amendment. Black rot (Xanthomonas campestris) was greater in the treatment that received vermicompost + pelletized chicken manure relative to the treatment that received a mixture of plant and animal byproducts across the three farms, and at one farm this reduced crop yield. Acorn squash is being grown in these plots in 2014 and a solanaceous crop will be grown in 2015. Field days will be held at the other farms in 2014 and 2015, and all collaborators will share their experience with participatory on-farm research in a workshop at a state-wide conference in 2016.