Many farmers report spreading large amounts of fertilizer with no improvement in yield. Before blaming fertilizer quality, one thing deserves checking first: soil acidity.
What happens on acidic soil
Below pH 5.5, phosphorus binds with aluminium and iron in the soil to form compounds roots cannot absorb. The phosphate fertilizer you paid for stays in the ground, in a form the crop cannot use.
- Phosphorus uptake efficiency can drop below 30% on strongly acidic soil.
- Aluminium dissolved at low pH is toxic to root tips.
- Microbial activity that decomposes organic matter also declines.
The right sequence
Measure soil pH first. If it sits below 5.5, spread 1 to 3 tonnes of dolomite per hectare depending on acidity, then plough it in evenly. Allow two to four weeks before fertilising so the lime can fully react.
“Liming is not an added cost, it is the condition that keeps your fertilizer spend from going to waste.”
One detail is often missed: never spread dolomite together with urea or ZA. The reaction releases nitrogen into the air as ammonia gas, and your fertilizer evaporates before it can be absorbed. Leave at least one week between them.
Tags
- Soil pH
- Dolomite
- Fertilisation