Farm Table says:
What is the problem?
Nitrogen (N), phosphorus (P), potassium (K) and sulfur (S) fertilisers are key inputs to maintain a productive, profitable and sustainable cropping industry in Western Australia (WA). However, excessive fertiliser use or inappropriate application practices can lead to significant nutrient pollution of land, water and air. Both under and over fertilisation may lead to economic losses.
What did the research involve?
The BFDC-WA project has collated and analysed relevant data from over 1890 trials to determine critical soil test values and critical ranges for P, K, S and N for wheat, lupin and canola grown in the WA wheat belt.
This study was the most comprehensive one ever completed for soil test information in WA and should serve as the benchmark for soil test interpretation for grain cropping in WA.
What were the key findings?
From the large data base assembled in this study, there is clear evidence of the value of increasing soil sampling depth to 30 cm rather than 0-10 cm as is current practice. Where relationships could be defined, they
have recommended critical soil test values for 0-10 cm sampling depth. However, users should be aware that often the soil test values in 0-10 cm were not reliable predictors of likely crop response to a nutrient (e.g. soil S
test for canola) or that soil test critical values varied among soil types for soil tests on 0-10 cm depth. They recommend greater frequency of sampling for the 0-30 cm depth when using soil tests for predicting the need for fertiliser for the no-till cropping systems of WA.
The soil test –crop response relationships presented are the best available information at this time but there is evidence that N and S relationships in particular can be improved by accounting for nutrient leaching and impact of
The cropping systems of WA continue to evolve as new technology is implemented. Also over time there are changes in the form, distribution and availability of nutrients that can have positive or negative impacts on nutrient availability.