Strategies to reduce nitrous oxide emissions from nitrogen fertiliser applied to dryland sorghum. Part 3. Residual impact of N applied in 2013−14 on sorghum grown in 2014−15

Abstract

Key findings • Very dry conditions during the 2013−14 summer meant that much of the nitrogen (N) fertiliser applied was not taken up by the sorghum crop, especially if it had been applied in-crop at booting. Between 46–65% of the applied N remained in the soil at harvest in 2013−14. • A following crop of unfertilised sorghum accessed the remaining N for crop growth and, at rates of 100 kg N/ha and above in the 2013−14 crop, increased grain yield and protein above the control. Late N application by topdressing in the 2013−14 crop gave similar crop production results to treatments where N was side-banded at sowing. • Two-year gross margins showed a significant benefit from N application as urea either at sowing or incrop.