101 Questions answered
Adapting Fertiliser Strategies in Drought: Less Upfront, More Targeted
Yes. During dry periods, crops tend to use fewer nutrients because:
- There is less root growth and exploration to access nutrients, and
- Crop roots can only take up nutrients dissolved in water, and soil water is very limited during drought.
If it has been dry for a few years, there will be residual fertiliser not used by previous (failed) crops. Although crops are using fewer nutrients, soil organic matter continues to mineralise—albeit slowly—adding to the pool of available nutrients.
It might be possible to cut back on fertiliser applications. It is important to soil test to check nutrient stocks. For nitrogen, apply a smaller amount at seeding and see how the season pans out. If it starts to improve, there should be opportunities to apply in-season nitrogen to meet crop demand. If it remains dry, unnecessary fertiliser applications have been minimised.
Look at potassium stocks (soil testing) and paddock yields. Most potassium removal occurs after heavy crops, particularly hay. Higher yields remove more potassium so it can be assumed that during drought, less potassium is removed.
Phosphorus might be stratified, especially in soils that have been no-till for many years. A small amount of starter phosphorus is a good idea.
Consider placing fertiliser closer to crop roots (but not too close to avoid fertiliser burn) to make it easier for crops to access nutrients if dry conditions are limiting root exploration.
