Delaying soil nitrate availability reduces nitrogen loss when growing sorghum on Vertosols

Abstract

Key findings • Nitrogen can be lost from the soil as gases, including the greenhouse gas nitrous oxide (N2O) particularly between when N fertiliser is applied at sowing and when plants establish a strong demand for N uptake. • To reduce the risk of this loss occurring, we trialled delaying the availability of soil nitrate supply to until the crop was well established through (a) using ENTEC® (urea coated with DMPP, a nitrification inhibitor), and (b) by applying urea at the booting growth stage. • Compared to urea applied at sowing, using ENTEC® reduced N2O emissions by 65–100%. However, since there was not waterlogging events, there was no grain yield benefit of the ENTEC®. • Delaying urea application until booting reduced N2O emissions by 95–100% compared to at‑sowing urea, but the dry conditions meant that the late applied N was not used to improve grain yield or protein above that of the nil‑N control.