Impacts of soil amendment history on nitrogen availability from manure and fertilizer.

摘要

Repeated, long-term additions of organic materials not only increase stocks of mineralizable soil N, but also bring about changes in soil characteristics that influence N dynamics. We conducted an aerobic incubation to explore how soil amendment history affects the transformation and availability of recently added N. Soil was collected from plots under contrasting amended and nonamended soil management systems in a 13-yr cropping systems experiment. Nitrogen source treatments were: no added N (control), NH4+ fertilizer (Fert), a net mineralizing manure (MManure), and a net immobilizing manure (IManure). Soil NH4+ and NO3- concentrations were monitored for 282 d. A two-pool, first-order model with fixed rate parameters was fitted to the NO3- accumulation data. When no N was added, net mineralization in the historically amended soil was twice that in the historically nonamended soil, mostly due to differences in soil total N stocks. When N sources were added, NH4+ consumption, net N mineralization, and estimated N pools were affected by both soil amendment history and N source, with a significant interaction between the two factors. Historically amended soil reduced the availability of recently added N relative to the nonamended soil. This reduction occurred in the active pool (N1) for MManure and in the slow pool (N2) for Fert. It appeared to be related to the timing of C availability. Future work modelling N availability should consider soil amendment history not only for its effects on soil N supply capacity, but also for its effects on the availability of recently added N sources..