Dairy manure N mineralization estimates from incubations and litterbags

• Published in: Biology and fertility of soils 2006-12, Vol.43 (2), p.145-152
• Main Authors: Cusick, P. R, Powell, J. M, Kelling, K. A, Hensler, R. F, Muňoz, G. R
• Format: Article
• Language: English
• Subjects: Biogeochemistry; Manures; Mineralization; Mineralogy; Nitrogen; Soil fertility
• ISSN: 0178-2762; 1432-0789
• DOI: 10.1007/s00374-006-0071-z

A laboratory incubation trial and a field litterbag study were conducted to determine the rate and magnitude of mineralization of dairy manure N components in a south central Wisconsin silt loam. Dairy manure components (urine, feces, or bedding, each ¹⁵N-labeled and the other components left unlabeled) were incubated in soil at 11, 18, or 25°C. Samples were taken at 14, 21, 42, 84, and 168 days and analyzed for mineralized N (NH4+ and NO3-) and ¹⁵N abundance in the inorganic and organic fraction (at day 168 only). In the field study, nylon mesh (38 μm) litterbags filled with ¹⁵N-labeled manure (2000) or unlabeled manure (2000 and 2002) were placed 7.5 cm below the surface and excavated at 7, 14, 21, 28, 35 (2000 only), 42, 56, 84, 98, and 126 days after burial and at corn (Zea mays L.) harvest, after 142 days in 2002 and 154 days in 2000. In the incubation study, 50-60% of applied urine N was mineralized showing the importance of this manure N component as a source of plant available N. About 14-19% of applied N was mineralized from the fecal and bedding components. In the litterbag experiment, approximately 70% of the dry mass and 67% of the N was mineralized from the litterbags with similar amounts measured using either labeled or unlabeled N. Rates of manure organic matter decomposition and N mineralization were best predicted using single exponential models for both years with most of the release occurring during the first 21 days.