Influence of soil faunal communities on nitrogen dynamics in legume-based mesocosms

Abstract

Soil invertebrates play an important part in nutrient supply. It has been suggested that invertebrates have the greatest influence on nitrogen (N) availability in soils of low N fertility, and therefore invertebrates may be less important in pastoral systems with high N inputs. The influence of invertebrates on N cycling, and the fate of 15N-labelled plant litter, in a low- or high-N environment and in a soil with low or high bulk density were explored by the introduction of different elements of the invertebrate community in constructed soil ryegrass–white clover mesocosms. At high bulk density and low N, the N made available by invertebrates resulted in higher plant growth, without any increases in N losses to the environment. At high N, where pasture growth was not limited by N, the N made available by invertebrates increased both herbage N% and the amount of N in leachate. More of the 15N-labelled plant litter decomposed in high-N than low-N mesocosms. Invertebrates increased the plant uptake of surface-applied 15N plant litter. The influence of invertebrates was dependent on bulk density, suggesting that invertebrates in compacted soils improved soil structure and N availability. This mesocosm study highlights the important role of invertebrates in N supply across a range of soil conditions.