Delaying nitrogen fertiliser application improves wheat 15N recovery from high rainfall cropping soils in south eastern Australia

Abstract

Improving nitrogen (N) fertiliser uptake of crops growing in soils susceptible to waterlogging could potentially reduce fertiliser input costs and harmful losses of N to the surrounding environment. The fate of 15N labelled urea applied to wheat cv. Bolac was studied on brown chromosol soils at Hamilton and Tarrington, in the high rainfall zone of south western Victoria, in south eastern Australia. Wheat was fertilised with 15N-urea solution, either deep banded 0.1 m below the seed at sowing or top-dressed with or without the nitrification inhibitor DMPP (3,4-dimethylpyrazole phosphate or ENTEC®) later in the crops development. Daily temporal topsoil (0–0.1 m) water was monitored, throughout the growing season, and at physiological maturity the recovery of 15N-urea in straw, grain and soil (to 0.4 or 0.6 m depth) was measured. Delaying untreated 15N-urea application until top-dressing at mid-tillering to first node stage of growth resulted in significantly (P 2.8 %) and the potential for large rates of mineralisation during the growing season.