Mind your Ps and Ks HGCA

By FWi staff

THERE are strong financial and environmental reasons for reducing or omitting potassium (K) and phosphate (P) inputs to some cereal crops, a Home-Grown Cereals Authority funded research review has concluded.

P and K inputs in cereals account for 10-15% of viable costs, amounting to a total £185 million a year.

Regular use of these nutrients has greatly improved the fertility of arable soils in England and Wales, but such generous use of PK fertilisers is now being questioned due to financial pressures to reduce variable costs, and environmental concern over eutrophication.

P and K inputs could be reduced by taking full account of soil PK residual levels and the nutrient value of organic manures, said a spokesman from the HGCA.

“Cereal crops do not respond to additional inputs once a critical residual level is reached,” he added.

Field evidence from the research indicates that standard soil tests and the traditional `maintenance approach to PK management do not work well on all soil types.

As a result the review has called on new principles of precision farming to be developed.

Paul Withers of ADAS Bridgets said that the recent introduction of the revised Code Of Good Agricultural Practice For The Protection Of Water (MAFF 1998) restricts the use of phosphates in UK agriculture.

“There is increasing justification for more precise information on P fertiliser strategies, for economic and environmental sustainability,” he added.