Plant litter variability and soil N mobility

Laboratory incubation studies were used to investigate whether and how variability of different plant litters modifies the mobility of nitrogen in soil. Fallen plant foliage from native New Zealand plants of diverse fibre and nutrient content were selected, with C:N ratios ranging from 14 to 102. Different litters provided substantially different inputs of macro-and micronutrients to soil that affected the mobility of N. Both fibre content and C:N ratios were influential. A primary effect of litter addition to soil was modification of pH, largely attributable to calcium enrichment. Nitrate in soil was reduced by up to 85% following litter amendments. Incorporation of five native plant litters into soil significantly suppressed emissions of nitrous oxide. We interpret these findings in the context of plant residues from naturalistic planting on the borders of farm paddocks that may play a role in tightening the N cycle and restricting spillover of nitrogen pollutants to the wider environment.