Short-term nitrogen transformations in soil amended with animal manure

An improved understanding of N mineralisation and immobilisation processes in soil amended with animal manure is important for improving the prediction of net mineralisation of manure N. The gross N mineralisation rate was measured in two differently textured soils following incorporation of sheep manure under laboratory conditions. The gross N mineralisation resulting from the decomposition of incorporated manure was compared to the mineralisation of identical, but N-15-labelled manure, to test if the mean pool dilution method and a numerical approach (FLUAZ model) would give reliable estimates of gross N mineralisation in soil with incorporated manure. There was good agreement between the methods, indicating that they are suitable for estimating gross mineralisation of manure N. About 12% of the organic manure N was gross mineralised after 7 days of decomposition, but there was no net N mineralisation due to the manure. The soil type did not influence the gross mineralisation of manure N during the first 7 days following application, and the gross nitrification rate was not significantly influenced by the manure amendment. The results suggest insignificant influence of manure on the gross mineralisation of soil N. (C) 2001 Elsevier Science Ltd. All rights reserved.