Methodologies for estimating nitrogen transfer between legumes and companion species in agro-ecosystems: A review of 15N-enriched techniques

Abstract

Methodologies based on 15N-enrichment for estimating the transfer of nitrogen (N) between legumes and companion non-legume species in agro-ecosystems are critically reviewed and classified according to whether they (i) are direct or indirect (ii) are dependent or independent of the measurement of yield and (iii) are estimating transfer of legume N, biologically-fixed legume N, or non-legume N. The two most commonly used methods are the indirect 15N isotope dilution method and the direct 15N shoot-labelling method. Published estimates both within and between agro-ecosystems are very variable, ranging from 0 to >50% of the N present in a companion species estimated to have been derived from a ..