Wayne Foot, Northern Regional Manager Summit Fertilizers, with local Area Manager Tracey Hobbs in the 2021 Wyalkatchem potassium and nitrogen trial.

There has been a lot of talk in recent months on potassium (K) nutrition and current prices. Growers obviously want to make the best fertiliser choices for 2023, and they can only make those decisions based on the best information we have at hand.

It led me to recalculate the returns based on Tracey Hobbs’ 2021 nitrogen (N) x K trial in Wyalkatchem. The information in the graph and table below compares three K rates (applied up-front) and five N rates. The phosphorus rate for all treatments was 10kg/ha.

I thought it would be interesting to compare the return on fertiliser investment (ROI = grain value less K and N cost) for the prices that existed in 2021 against January 2023 values.

Coming off some good summer rains the trial was sown on May 13 to Scepter wheat. February to October rainfall for the area was 445mm with some excellent yields achieved.

In scenario 1, the Summit Fertilizers list price in April 2021 was used to calculate K and N costs. Grain values were based on Kwinana deliveries on November 18, 2021. For scenario 2, 2023 January prices for fertiliser and Kwinana grain deliveries were used.

The trial graph shows yield responses to both K and N. Importantly, the ROI calculations (see table) showed yield alone didn’t tell the whole story, and grain quality also had a significant influence on fertiliser returns.

The key message would be that well balanced nutrition will remain the best nutrition for the coming season.

For example, while the grain yield for the K0 x N120 treatment was relatively good, the cost of extra N and downgraded grain quality punished the ROI.

Increasing the fertiliser cost in scenario 2, didn’t really change the order of results when it came to ROI, because there was more to be factored into the equation than just the direct cost.

If your soil has shown it is K responsive, it will remain an important nutrient this season.

Article by Wayne Foot, Northern Regional Manager