Improving nitrogen use efficiency in irrigated cotton production

Abstract Irrigated cotton in Australia is mainly grown on heavy textured soils which are prone to waterlogging, resulting significant losses of nitrogen (N) via denitrification and surface run-off. This study investigated fertiliser use efficiency (fNUE) over three seasons five commercial farms using the 15 N tracer technique. Fertiliser NUE was consistently low across all fertilised treatments, with average 47% applied lost only 17% taken up by crop derived from fertiliser. There no effect different products rates lint yield. High yields (0.9–3.6 Mg ha −1 ) could be achieved even without application fertiliser, demonstrating mineralisation soil organic N, residual or returned residues, as key source these cropping systems. Using nitrification inhibitor DMPP overhead instead furrow irrigation showed potential reduce losses. The results demonstrate that under current on-farm management fNUE irrigated highlight need account for stocks when assessing optimized rates. substantial scope improve any impact yield, adjusting rates, particular combination DMPP. a promising approach not water efficiency, but also