Denitrification contributing to crop N deficiencies in 2012: analysis using ‘NBudget’ and soil test data

Abstract

Key findings • Widespread N deficiencies of cereal crops were evident in northern NSW during the 2012 winter season, culminating in receivals of large amounts of low protein grain. • We used ‘NBudget’, the NSW DPI CropMate-based decision-support tool, to predict sowing soil nitrate levels for a number of the 2012 experimental sites and compared with measured values. • Greatest differences between predicted and measured soil nitrates were at the sites that either had the highest fallow rainfall or were inundated with floodwater, suggesting denitrification losses of N may have been a contributing factor. • Due to the difficultly in predicting denitrification losses, growers are advised to consider deep coring for nitrate testing, particularly following saturating rainfall or flooding as was experienced during the 2011–12 fallow.