Toward Effective and Sustainable Fertility Management in Organic and Low Input Indiana Vegetable Production Systems: An Integrated Approach.

Consumer demand for organically produced crops is on the rise. As a result, organic vegetable production in Indiana has steadily expanded in acreage and number of producers. These growers generally rely on fertilizers that are not readily available to plants. Such amendments must be mineralized and transformed by soil microorganisms before being taken up by the crop. We seek to determine the impact of commonly used alternative fertility practices on common indicators of soil quality, soil microbial ecology and plant productivity. Over three growing seasons, application of composted chicken manure and a green manure (hairy vetch) will be compared to a conventional fertility treatment and an unamended control in open field and high tunnel settings. Baseline and seasonal soil samples will be collected to determine treatment impacts on common indicators of soil quality. In the open field setting, overall microbial community composition will be estimated using T-RFLP of 16S rDNA, and the abundance of genes involved in nitrogen transformations (amoA, nirS, nirK and nosZ) will be quantified using qPCR. Sweet peppers (Capsicum annuum) will be grown to determine treatment impacts on plant productivity and disease pressure as well as act as a biological indicator of nitrogen availability. In 2011, crop yield (Swiss chard, Beta vulgaris) was greatest in the urea treatment, followed by the composted chicken manure, while the green manure and unamended control produced similar yields in both fresh and dry weights. Analyses of soil samples collected during the 2011 growing season are in progress. We expect greater soil quality, microbial community diversity and nitrogen cycling gene abundance in the alternative fertility treatments compared to the conventional and unamended control. Assessing how alternative fertility practices influence ecological functioning and plant productivity will broaden the understanding of the scientific community on how alternative fertility practices impact soil microbial ecology, and lead to improved fertility management for organic and low input growers.