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 15N-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.