Impacts of Soil Amendment History on Nitrogen Availability from Manure and Fertilizer
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 transfor-mation 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, fi rst-order model with fi xed 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 non-amended 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 non-amended 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 modeling 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.
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| Publication | Soil Science Society of America Journal |
|---|---|
| Section | 035 |
| Author | E.B. Mallory, T.S. Griffin |
| Volume | 71 |
| Number | 3 |
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