Transformation of nitrogen and nitrous oxide emission from grassland soils as affected by compaction

Animal trampling is one of the main factors responsible for soil compaction under grazed pastures. Soil compaction is known to change the physical properties of the soil thereby affecting the transformation of nitrogen (N) and the subsequent of release of N as nitrous oxide (N2O). The form of N source added to these compacted soils further affects N emissions. Here we determine the interactive effects of soil compaction and form of N sources (cattle urine and ammonium, nitrate and ureafertilizers) on the loss of N through N2O emission from grassland soil. Overall, soil compaction caused a seven-fold increase in the N2O flux, the total N2O fluxes for the entire experimental period ranged from 2.62 to 61.74 kg N2O-N ha(-1) for the compacted soil and 1.12 to 4.37 kg N2O-N ha-1 for the uncompacted soil. Among the N sources, the highest emissions were measured with nitrate application, emissions being 10 times more than those from other N sources for compacted soil, suggesting that the choice of N fertilizer can go a long way in mitigating N2O emissions in compacted grasslands. (C) 2006 Elsevier B.V. All rights reserved.