10 April 1998

SP rating only a guide

WITH good spreader management, farmers should be able to achieve good levels of accuracy – even with cheaper fertiliser products, insists Amazones Rod Baker.

This, however, is at odds with a statement made by merchanting company Cargill, which suggested that in a system using 24m tramlines and a twin spinning disc fertiliser spreader, only true granular ureas and UK ammonium nitrates can be spread with any degree of certainty to a Coefficient of Variation (CoV) close to 10%.

But Mr Baker, while conceding that an SP5-rated fertiliser will give least problems in application, is adamant that cheaper products can be spread to similar consistency – given proper setting data and careful management.

"The suggestion that savings from not using SP5-rated UK product may prove false economy is not entirely true," says Mr Baker.

And Mr Baker goes on to question the degree farmers should rely on spread pattern ratings (SP).

"Farmers should use a fertilisers SP rating only as a guide; a products definitive rating still appears to be based on the test results of a single batch, in spite of the fact that there are a number of factors which can alter the specification of a product during the season," he says. &#42