Evidencing overwinter loss of residual organic and clay-fixed nitrogen from spring-applied, 15N-labelled pig slurry

Chantigny, M. H., Angers, D. A., Rochette, P., Pomar, C. and Pelster, D. E. 2014. Evidencing overwinter loss of residual organic and clay-fixed nitrogen from spring-applied, 15 N-labelled pig slurry. Can. J. Soil Sci. 94: 1–8. In northern areas, it is assumed that soil residual mineral N measured at harvest represents the pool at risk of environmental loss during the non-growing season. Using 15N-tracing techniques we determined (i) the distribution of side-dressed pig slurry N in the mineral, organic and clay-fixed N pools of sandy loam and clay soils, and (ii) whether 15N found in each individual pool at harvest is retained or lost during the non-growing season. Pig slurry labelled with 15N was side-dressed to corn (four-leaf stage; 100 kg ha−1 total N) and traced in soil (0–60 cm) and plants for 2 yr. Pig slurry contained 60% of its N as NH4. During the growing season, applied N accumulated in the clay-fixed N pool in the clay soil, and in the organic N pool in both soils. At harvest, less than 5% of s...