Graeme A. Sandral1, Ehsan Tavakkoli1, Felicity Harris1, Eric Koetz1 and John Angus2
1 NSW Department of Primary Industries, Wagga Wagga Agricultural Institute, Pine Gully Rd, Wagga Wagga, NSW 2650, Email email@example.com
2 CSIRO Agriculture and Food, PO Box 1700, Canberra ACT 2601 and EH Graham Centre, Charles Sturt University, Locked Bag 588, Wagga Wagga, NSW 2678
Experiments in controlled conditions have shown possible improvements in nitrogen use efficiency from concentrating ammonia-based fertiliser in bands mid-way between crop rows. The advantages result from delaying nitrification of fertiliser by suppressing nitrifying microbes. This is best achieved at high concentrations of ammonium resulting in a slow prolonged release of nitrogen (N) to the crop. This technique known as mid-row banding (MRB) offers potential to, reduce excess seedling growth, lower denitrification and nitrate leaching losses, reduce immobilisation and provide an opportunity for root proliferation around the ammonium band at a time of high plant N demand. These advantages have not been shown conclusively in field based studies.
In a preliminary field experiment, urea was banded at sowing between every second wheat row at concentrations sufficient to temporarily suppress nitrifying bacteria (Mid-row banding [MRB]). Nitrogen offtake in grain was higher with MRB urea than urea broadcast and incorporated by sowing for both Beckom and Spitfire at the 80, 120 and 160 kg/ha rates of N application. Apparent fertiliser recovery in grain was also higher from MRB urea than from urea broadcast and incorporated by sowing in five of the eight treatment comparisons. Soils cored at stem elongation from the MRB treatment showed higher ammonium levels in the top 20 cm and lower nitrate concentration at 60-100 cm than urea broadcast and incorporated by sowing. Roots proliferated around and below the original MRB. These results indicate potential for MRB to improve N use efficiency.