20 March 1998

Benefit mix may lift compost value

FERTILISER value could make composted waste worth up to £2/t on farms, but take into account other benefits and it might fetch £5 delivered.

That is the conclusion of a report by Levington Agriculture on field trials for the Environment Agency on behalf of the then Department of the Environment.

The research suggests that the organic matter and trace element content of compost, in this case made of separated green waste from Suffolk civic amenity sites, and the better plant establishment it encourages, can be worth £3/t.

The compost, made by Needham Market-based County Mulch Company, was found to have some slight liming value. At 25-50t/ha it also supplied enough potassium for normal maintenance.

But because the soils were already relatively fertile and alkaline, some of the advantages, like better release of phosphorus, may have been masked.

Main finding was that oilseed rape plant populations were much better in the autumn on the heavier soil given at least 25t/ha. As little as 12.5t/ha improved plant vigour in November. But by spring only plots with the higher amount remained more vigorous.

On the light soil the compost did not affect plant populations but did boost autumn vigour. However, by spring only the highest rate (100t/ha) was still showing any signs of improvement. &#42

COMPOST VALUE

&#8226 £2/t for fertiliser.

&#8226 £3/t for other benefits.

&#8226 More OSR plants on heavy land.

&#8226 Most benefits transient.

&#8226 Yield unaffected short term.