Trial studying the timing of late nitrogen applications in wheat post-flowering at Brookstead, Queensland.
PHOTO: Linda Bailey
Figure 1 Mean impact of late foliar application of nitrogen on grain protein in 2012.
GRDC-funded trials through the Northern Grower Alliance (NGA) from 2012 to 2014 evaluated the effectiveness of applying nitrogen to wheat crops from full flag-leaf emergence onwards.
The trials assessed the effect of nitrogen on grain yield and quality, and profit, and whether there was an optimal method or timing for late nitrogen application. The two wheat varieties evaluated were EGA Gregory and Suntop – both consistently high yielding, but with generally lower protein levels than other varieties.
Richard Daniel, chief executive officer of NGA, says the results suggest that trying to increase wheat protein with late foliar nitrogen application is a high-risk tool, particularly in areas where spring rainfall is erratic.
“Economic benefits from targeting nitrogen budgets to maximise yield is, in most cases, far easier and more profitable than trying to manipulate protein levels with late nitrogen applications,” Mr Daniel says.
“The trials clearly showed that late foliar applications of nitrogen are capable of lifting protein levels but we were generally unable to generate any net benefit,” he says.
to two per cent increases in protein. However, benefits of this level occurred when the wheat protein, without additional nitrogen was less than 10 per cent. Increasing nine per cent grain protein to 10 or 11 per cent frequently doesn’t have any impact on grain price.”
Out of the 15 trials (Table 1), net benefits were only obtained in one trial, and at that site from only four of 14 foliar nitrogen treatments. The level of net benefit ranged from $9 per hectare to $33/ha.
“Unless we can improve the efficiency of the conversion of applied nitrogen to protein dramatically, grain grade price differentials of at least $20 to $40 per tonne are probably necessary before even considering this type of approach,” Mr Daniel says. “Unfortunately, we only experience these sorts of returns in two or three years out of every 10, making it economically unviable.”
In eight of the 15 trials, applying the same level of additional nitrogen earlier in-crop (at planting or in-crop at jointing) was shown to be a more economic option to improve both protein and yield.
Figure 2 Mean impact of late foliar application of nitrogen on grain protein in 2013.
Figure 3 Mean impact of late foliar application of nitrogen on grain protein in 2014.
||Fertiliser and application cost
|Croppa Creek 2012
||No change ASW
||ASW to H2 (+$9/t)
||No change HPS1
||No change HPS1
||GS60–65 (20kg N/ha rate)
||ASW to APW (no change in grain price)
Table 1 Economic analysis of the largest net benefit foliar treatments that provided a significance increase in grain protein – over the series of 15 trials.
Urea solution cost 2012 and 2013 $0.46/L ($76/ha at 40kg N/ha), 2014 $0.43/L ($72/ha at 40kg N/ha).
Application cost: $8/ha.
Grain prices/t: 2012 ASW $237; 2013 HPS1 $251, APW $256, H2 $265; 2014 ASW and APW $267.
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