Field Research & Agronomy

Grain protein & nitrogen response in cereal varieties

AIM:

‍To assess the nitrogen response of wheat and barley varieties and the accuracy of the nitrogen calculators in season recommendation to achieve 10.5% and 12.5% grain protein on heavy red soil.

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• Due to the lack of growing season rainfall, there was very little growth and minimal nitrogen response when NDVI was measured on the 20th July.
  Subsequently, after above average rainfall in August, the N-calculator had underestimated yield and N requirements.

Summit’s In-Season Nitrogen Calculator aims to calculate a precise N rate to maximise the yield potential of a paddock where a crop is starting to run into N limitations, using NDVI as a real-time growth measurement.
It is designed to utilise comparisons between crop growth without N limitations beside paddock practice to determine optimal N application for yield and returns.

After above average rainfall in August and September, actual yields were between 1.75 and 3 t/ha where the N-Calc had predicted 1.12 to 1.89t/ha.

Notable also is the yield and protein response to the N-gauge treatments of 104 kg/ha of nitrogen upfront.
Under a normal growth pattern, upfront N would have been utilised to grow tillers, however limited rainfall until August meant N was remaining to be converted into protein.

BARLEY

CONCLUSIONS:

• Due to the lack of growing season rainfall, there was very little growth and minimal nitrogen response when NDVI was measured on the 20th July.
  Subsequently, after above average rainfall in August, the N-calculator had underestimated yield and N requirements.
• Protein responded positively to nitrogen although N-calc top-ups were below the 10.5% and 12.5% protein targets, attributed to the underestimated yield prediction in July.
• There was a significant yield response to nitrogen rate, with barley varieties (2.31-2.97t/ha) yielding greater than wheat (1.74-2.59 t/ha).
• Gross returns were maximised by the higher yielding barley varieties and from ASWN wheat with the noodle price premium.