Nitrogen application key to increased yield for Tasmania’s cereal crops
Nitrogen fertiliser is a key determinant of grain yield and the ability of cereal crops to achieve yield potential in Tasmania.
In this article, senior agronomist Simon Nowell of Elders Devonport discusses why predicting nitrogen supply is complex but necessary.
“Because nitrogen fertilisers are one of the largest variable cost inputs (especially in Tasmania) accurate predictions of nitrogen requirements are critical for grower profitability,” says Simon.
“Predicting nitrogen supply to crops is complex because nitrogen demand by the crop is related to actual yield, which is determined by seasonal conditions including the amount and timing of the growing season rainfall.”
Simon finds that there is generally a poor relationship between pre-sowing soil-test nitrogen and yield response of wheat to applied nitrogen, usually caused by an effect from stored water and in-season rainfall.
“This season has seen most areas in Tasmania receive above average rainfall, so top-dressing nitrogen into wheat crops is very important,” says Simon.
“The pattern of crop demand for nitrogen during the growing season also has to be considered. The highest demand is when the crop is growing most rapidly. In-crop soil sampling can help to identify how much N is being mineralised,”
“Fertiliser recommendations for nitrogen are generally based around a budgeting approach, using a series of relatively simple, well developed equations that estimate plant demand for nitrogen supplementation and the soil’s capacity to supply the fertiliser.”
Simon says that Tasmanian wheat crops chasing higher yield may wish to consider top-dressing nitrogen at growth stage, GS 30-31, and again at GS32-33. The amounts applied can be calculated with the results of an in-crop soil test.
“Growers should work with their agronomist to determine a soil testing strategy. An agronomist can make all the difference in helping to interpret and analyse the test results to determine a crop nutrient strategy for the season.”
For further advice contact your local Elders agronomist.