Australia
June 16, 2014
Northern region grain growers should be soil testing at depth to obtain a clearer understanding of their fertiliser needs for key immobile nutrients like phosphorus and potassium during the winter season.
Dr Mike Bell (pictured), from the University of Queensland’s Alliance for Agriculture and Food Innovation (QAAFI), says soil testing is important to understanding the status of these key nutrients, of which native stocks in the soils have been run down over time.
“Across the region there is huge variability in P status. “Some soils have a heck of a lot and still have a lot; others started with not much and now the well is dry, particularly in the sub soils,” Dr Bell said.
“Knowing what you’re on is absolutely critical. Soil testing in the subsoil (10-30cm layer) as well as in the topsoil (0-10cm) for potassium and phosphorus is really important.
“Before you lurch into a fertiliser program, you’ve got to know what you’re sitting on.”
A team led by Dr Bell is conducting trial work supported by the Grains Research and Development Corporation (GRDC) assessing the costs and returns of deep P placement in cropping systems using simulated crop yields in combination with trial data from sites in northern NSW and Queensland.
Dr Bell said applying P at sowing was still an important practice for grain growers, but it only supplied a small amount of the nutrient to the crop.
Click on the audio icon above to hear Dr Mike Bell from the University of Queensland’s Alliance for Agriculture and Food Innovation (QAAFI) discussing sub-soil testing. This will open the file in a web browser. Right click on this web page and select ‘Save as’ to download the mp3 file for playback.
Longer term strategies, including deep placement of nutrients, were required to manage levels over the full cropping cycle, rather than on a needs basis crop-by-crop.
“Residual value of applied P for subsequent crops is generally good, and responses are recorded over multiple crop seasons,” he said. “This holds the key to profitability of deep P applications, which can be made infrequently to cater for varying seasonal conditions and stubble loads.”
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