How Requirements Increase with Yield Potential
Crop requirement for potassium will increase with higher yield potentials due to improvements in:
• plant breeding
• farming systems
• application of other limiting nutrients.
In the years following World War II, average Australian wheat yields were just over 1.0 t/ha. Today the Australian average is over 2.0 t/ha because of agronomic improvements including pest and disease control, mechanisation and improved nutrition, varieties and rotations.
More recently, conservation farming systems which protect soil structure and improve soil water storage have improved yields in dry years and increased opportunities for double cropping. These improvements have increased both crop demand for potassium and its export from the field.
Where wheat yield is improved by the application of nitrogen and phosphorous, potassium uptake rates can be much higher. (See graph.)
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Potassium uptake of wheat increases dramatically where nitrogen and phosphorous are supplied. |
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Improved yield potential due to nitrogen and phosphorous fertilisation may not be achieved if adequate potassium is not also applied. (See photo.)
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In this on-farm experiment, one plot received nitrogen, phosphorous and potassium fertiliser, while the other plot received only nitrogen and phosphorous. |
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