While stubble burning provides many benefits to soil structure, weed control, pest and disease reduction, and cost to the farmer in terms of cultivation practices; it can also affect soil nutrient status:

1. Carbon that is not combusted to CO2 and CO (30-50%) is returned to the soil surface as a biologically inactive charred residue. This can decrease the quality and quantity of organic matter in the soil, reducing water-holding capacity and stores of nutrients.

2. Ash produced from burning stubble is alkaline, and can increase the pH at the soil surface rapidly.

3. Soil nutrient losses depend on the temperatures reached, however, the majority of nitrogen, carbon, and sulphur in burned residues will be lost to the atmosphere.

4. Further losses of nutrients can occur through wind and water wash of ash from paddocks.

Therefore, it is a good idea to have soil tests completed to determine what nutrients are lacking after post-harvest residual removal.

The above information was sourced from the Review of the role and practices of stubble burning in New Zealand, including alternative options and possible improvements, and can be found on the FAR website.