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Title: COMPOST MINERALIZATION IN SOIL AS A FUNCTION OF COMPOSTING PROCESS CONDITIONS

Author
item Cambardella, Cynthia
item RICHARD, T - IOWA STATE UNIVERSITY
item RUSSELL, A - IOWA STATE UNIVERSITY

Submitted to: European Journal of Soil Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/16/2002
Publication Date: 1/4/2003
Citation: Cambardella, C.A., Richard, T.L., Russell, A.E. 2003. Compost mineralization in soil as a function of composting process conditions. European Journal of Soil Biology. 39(3):117-127.

Interpretive Summary: Swine production agriculture in the Upper Midwest has changed rapidly in the last 10 years, with equal numbers of animals being produced in fewer, larger facilities. A natural consequence of this is an increase in localized production of manure. Field application of liquid swine manure and storage of the manure in lagoons can potentially lead to environmental pollution of air, surface waters and groundwater. Alternative animal management systems, such as deep-bedded swine manure management systems, and especially hoop structures, allow economically competitive swine production and appear to also provide reductions in odor emission and water quality risks. Composting manure produced from these alternative systems can further reduce the cost swine production by decreasing the cost of transporting the material to the field. This laboratory study evaluated the impact of compost quality and composting process conditions on nutrient cycling after compost incorporation in soil. We found that compost quality and composting process conditions affected soil carbon and nitrogen cycling after compost incorporation by increasing C mineralization and delaying the release of inorganic N. This research provides scientists with new information about the effects of compost incorporation on soil C and N dynamics which will ultimately be used to optimize compost management practices.

Technical Abstract: Compost has been shown to have a range of positive impacts on soil quality and can provide an important source of nutrients for plants. While these benefits have been documented for many finished composts, there is presently little understanding of the impact of composting process conditions and the extent of compost decomposition on soil C and N mineralization after compost incorporation. This study investigated the effects of moisture content, C/N ratio, and the use of blended soil or biofilter covers on the composting of swine manure mixed with corn stalk bedding and the subsequent effects of these treatments on soil C and N mineralization after compost incorporation. Dried, ground composts were blended with equal parts of quartz sand and soil and incubated aerobically for 28 days at 30 degrees C. Cumulative respired CO2-C and net mineralized N were quantified. Results indicate that (1) organic substrates that did not degrade due to sub-optimal conditions during the composting process can readily mineralize after incorporation in soil; (2) C and N cycling dynamics in soil after compost incorporation can be affected by compost feedstock, processing conditions, and time; and (3) denitrification after compost incorporation in soil can limit N availability from compost. The composts used in this study were significantly altered by drying and grinding relative to moist the heterogeneous composts typically applied in agronomic settings. Further studies with unaltered compost in larger scale systems will be needed to better understand the nature and implications of C and N dynamics in compost amended soil.