Responsive nitrogen (N) management optimises grain yield and grazing value from dual-purpose crops. Dual-purpose crops are sown early, grazed during winter, then grown on to produce grain. For dual purpose crops in the southern region the framework for N nutrition should be:
- Apply adequate N upfront to promote vigorous forage growth for grazing.
- Crops sown in February / March need 150 kg of available N /ha.
- Crops sown in April need around 100 kg N /ha.
- Topdress post-grazing for grain yield based on N budget.
- Additional N is usually required even though some N is recycled through manure and urine.
- Wheat needs about 40 kg, and canola around 80 kg of N for every tonne of grain produced.
- Yield increases often cover the cost of the additional N application.
- Exclude livestock for at least two weeks after topdressing N to reduce risk of nitrate poisoning.
John Kirkegaard is a farming systems agronomist at CSIRO in Canberra.