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Title: Compost: a potential value-added product for dairy operations?

item SHANE, ERIKA - University Of Minnesota
item ENDRES, MARCIA - University Of Minnesota
item Russelle, Michael
item ROSEN, CARL - University Of Minnesota
item JOHNSON, DENNIS - University Of Minnesota

Submitted to: Applied Engineering in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/3/2010
Publication Date: 3/1/2011
Citation: Shane, E.M., Endres, M.I., Russelle, M.P., Rosen, C.J., Johnson, D.G. 2011. Compost: a potential value-added product for dairy operations? Applied Engineering in Agriculture. 27(2):225-233.

Interpretive Summary: Many farms import more nutrients in fertilizer and livestock feed than they export as products. This can result in excess nitrogen or phosphorus accumulating in the soil, increasing the risk of environmental contamination. Manure produced by livestock is an excellent product for recycling nutrients on the farm, but it is difficult to transport away to improve the farm's nutrient balance. A partial solution may be for farmers to compost the manure into a commercial product that can be purchased by others. We evaluated the composting process in a new type of dairy cow manure from deep-bedded packs based on different bedding materials, from wood chips and sawdust to corn cobs. As expected, these mixtures composted at different rates. Mixtures based on woody materials did not begin active composting for 2 to 4 weeks, while those based on crop residues heated quickly. All mixtures reached temperatures high enough to kill pathogenic organisms. Despite active management of the compost piles, none completed the process during the nearly 5-month-long study. It appeared that composting may have been slowed when too much moisture was lost from some mixtures. Composting this new type of manure appears to be feasible, but farmers will need to monitor and adjust compost temperature and moisture frequently.

Technical Abstract: The objective of this study was to evaluate the composting potential of various bedding materials that were previously used in experimental compost-bedded packs for dairy cows. Each material was placed in windrows (1.8 m high, 9.1 m long, and 2.3 m wide) from April 2007 to September 2007 and managed as needed to promote composting. Materials included: sawdust (SD) (control), corn cobs (CC), woodchip/sawdust mix (WC/SD), soybean straw (SS), woodchip/soybean straw mix (WC/SS), and soybean straw/sawdust mix (SS/SD). Replicated samples were taken weekly and analyzed for dry matter (DM). Carbon:nitrogen ratio (C:N ratio), pH, total C, total N, NH4-N, and NO3-N were measured once monthly. Temperature was measured twice weekly. Total P, total K, and EC were measured at initial and end of period. None of the windrows had a significant decrease in temperature from day 1 to day 141, but all materials had a major reduction in coliforms. CC, SS/WC, WC/SS, and SS were the only materials that decreased (P < 0.05) in moisture content from day 0 to day 138. Materials were similar when comparing day 0 and day 138 for NH4-N, NO3-N, and inorganic N concentrations. SS, SS/SD, WC/SS, and WC/SD all decreased (P < 0.05) from day 0 to day 138. Some of the observed C:N ratios were slightly below 20:1, with the exception of SD and WC/SD at the end of the period. Based on these results, all materials composted during the time period and would potentially work as a soil amendment/mulch if proper composting takes place.