Nitrogen Immobilization and Mineralization Kinetics of Cattle, Hog, and Turkey Manure Applied to Soil

Nitrogen mineralization and immobilization following manure application are critical processes influencing plant N supply and offsite N losses. We conducted laboratory experiments to examine the influence of these two processes in addition to N oxide gas production on N availability for 180 d following manure addition. A Tara loam (fine-silty, mixed, superactive, frigid Aquic Hapludoll) and a Webster clay loam (fine-loamy, mixed, superactive, mesic Typic Endoaquoll) amended with liquid dairy (Bos taurus) manure (LD) were incubated at 25 and 10 degrees C, while Tara soil amended with solid dairy manure (SD) and turkey (Meleagris gallopavo) manure (T), and Webster soil amended with liquid hog (Sus scrofa) manure (H), were incubated at 25 degrees C. Maximum net N immobilization was 14 and 40% of the initial NH4+ concentration in H and LD, respectively, and persisted for 35 to 180 d. In LID, H, and T-amended soils, net manure N mineralization was not apparent, and there was good agreement between initial NH4+ content and available inorganic N from the manure. These data suggest that, for these manure types, estimates of first-season available N would be improved by measuring manure NH4+. In contrast, in soil amended with SID, which had the lowest initial NH4+ content, 22% of organic N was mineralized. Gaseous N losses were <1% of the added N in all treatments. The previously developed model NCSOIL was used to predict plant N availability and NO3- leaching potential with various manure incorporation dates. Under climate conditions typical of the Upper Midwest, no clear advantage of late fall compared with spring incorporation of manure with regard to N availability could be shown, but NO3- leaching potential seemed high with early fall incorporation.