Improving Soil Quality with Organic Amendments.

Environmentally sound and productive crop and soil management practices that promote soil organic matter content, use crop rotation and reduced tillage, and reduce pesticide inputs are essential for maintaining the soil resource. Surveys have verified the relationship between on-farm practices that promoted soil organic matter accumulation and increased soil quality. The objective the current study was to assess soil biological activities (bioindicators) for describing soil quality under sustainable agricultural practices. In controlled field studies organic amendments (poultry litter, municipal compost, commercial compost, cover crop residues) were applied in the spring in 2002, 2003, and 2004 to a Mexico silt loam (fine, smectitic, mesic, Aeric Vertic Epiaqualf) under soybean production in central Missouri. A biodynamic fertilizer (Effective Microorganisms [EM]) was included in split-plot treatments. Biological indicators including soil enzymes (selected to represent C and N transformations), soil respiration, water-stable aggregation, and microbial diversity were measured to assess impacts of organic amendment. Changes in soil microbial diversity due to organic amendment were detected and indicated direct effects of the amendments on soil biological processes by influencing the composition of the soil microbial community. Analyses of soil quality bioindicators demonstrated that organic composts and cover crops are of considerable value for use in improving soils in agroecosystems.