A new method to predict grain protein in milling wheat during the growing season

Growers receive a premium on their milling wheat if they reach protein levels above 12.5%. Usually the larger the yield, the lower the protein levels will be, unless extra Nitrogen is applied. It is difficult to ascertain mid-season whether more N is necessary to achieve the required protein level, because relatively small differences in N nutrition are involved; 30-40 kg of N might be enough to push protein over the threshold.

In this paper we describe the development of an accurate test to predict final protein in grain, using samples taken mid-May to mid-June, so that it is possible to add extra fertiliser if necessary. The test measures signals in the roots that are involved in the regulation of N uptake in response to the external N supply. Generally, when plenty of nitrogen is available, the N uptake efficiency will decrease and vice versa.

Measuring these regulatory signals provides a reliable assessment of the N status of the plant, and from this the final grain protein level can be predicted. Despite the difficult growing conditions in 2019, we were able to correctly predict protein levels as being < 12%, between 12 – 12.5%, and > 12.5% in 72% of samples, which all received between 180 and 360 kg/ha N fertiliser. Further field experiments have been conducted in 2019 and 2020, so that additional results can be presented in this webinar.