Tactical use of nitrogen in canola to manage risk and include break crops in northern Wimmera

A trial was undertaken to determine if N rates for canola can be reduced in the Wimmera without loss of yield. It also aimed to determine how late N can be topdressed. There was no response to a low rate of N, while 50 kg N/ha when applied at or near sowing gave a 54% yield increase, and 100 kg N/ha application raised yields a further 14%. Nitrogen rate is therefore very important, but timing—when applied even up until early flowering—had little effect. Soil test N at sowing was 41 kg N/ha, and this would have carried the crop through the early growth. The crop showed good recovery from N stress when N was applied as late as early flowering.

Growers in this region base the fertilizer program on expected N demand based on a water limited yield potential. A total 80 kg N/ha/tonne of grain yield—the popular “rule of thumb”—has stood up as the best treatment over a range of timings. However, results from this trial suggest a lower rate (60 kg) can provide similar yields as long as it is applied early.

This field experiment confirmed that canola can respond to late applied N (early flowering) but less efficiently than earlier applied N in a season with a dry spring. ANZ-12