Cut Phosphorus Fertiliser Costs

10 December 2007

FarmOnline Article 11th December 2007

Create biologically active soil by increasing organic matter and balancing nutrients - then monitor with regular APAL soil analysis to cut fertiliser costs.

Soil microbes can cut phosphorus costs

Australia
FarmOnline - Tuesday, 11 December 2007

With the cost of phosphorus fertiliser continuing to sit at record levels and farmers facing unprecedented fertiliser costs of up to $150 a hectare, any means of cutting down costs will be welcomed.

Researchers have found that a combination of building microbial activity and monitoring soil phosphorus levels to ensure expenditure is profitable are two good methods of minimising fertiliser bills next season.

South Australian scientist Ann McNeil, a researcher at the University of Adelaide, says soils contain organic phosphorus and by encouraging soil microbial activity, growers can encourage phosphorus cycling and increase its availability to the plant.

Traditionally, farmers have accessed in-soil nitrogen reserves, which become available through mineralisation following summer rain or through growing a legume, but have regarded phosphorus as an unavoidable expenditure.

Dr McNeil says growers can also make use of organic phosphorus in the long-term - with no-till systems improving the soil organic matter doing the best job of making extra P available.

Dr McNeill's research shows farming practices which build soil carbon also improve organic phosphorus levels and microbial activity.

However it is not a short-term fix – and that P levels must be maintained to promote microbial activity.

Even though as little as 20pc of applied phosphorus ends up in the plant, the "lost" fertiliser still has an important part in stimulating microbes and eventually becomes available to plants in other seasons.

Eighty to ninety per cent of phosphorus in the crop comes from the organic phosphorus reserves in the soil, converted by the soil microbes.

Dr McNeill says it takes a long time to achieve a nutrient balance in the soil but by encouraging the soil microbes growers can maintain a healthy system with a sustained ability to supply plant-available phosphorus.