16 January 1998

Aids help spot nutrient needs

GRASS nutrient needs could be met more precisely this spring using new soil test kits, computer programs and fertiliser tables to calculate applications.

The Institute of Grassland and Environmental Research project leader, David Scholefield, suggests that using these aids will allow applications to be cut by 25-30% while maintaining grass yields.

Dr Scholefield explains that the level of nitrogen available to grass is based on a complex of factors such as stocking density, soil type and local climate.

These affect leaching losses and the amount of nutrients received in the manure from grazing animals.

"A relatively small amount of nitrogen is removed from the farm when animals are sold and so as the season progresses there is a gradual accumulation of it in the soil," says Dr Scholefield. A proportion of the fertiliser applied is then wasted via leaching in the winter, an economic loss and a pollution risk.

Trials at IGER have sought to improve fertiliser efficiency by matching applications to soil indices using frequent soil analysis. As a result a simple test kit has been developed and will be available from spring.

"But this alone is not an accurate enough measure to base fertiliser regimes on, because nitrogen uptake changes according to grass growth, management policies and weather," he says.

This has led to the development of a computer program which has been undergoing farm trials for fine-tuning over the past two grazing seasons. Producers will be able to plug in data from their own units which can then be used in conjunction with the soil test kits to formulate fertiliser programmes.

For producers without a computer a ready reckoner table with the same parameters will also be available for use with the kits. &#42