31 May 1996

Sludge can be cash saver

SEWAGE sludge provides more nutrients than livestock manure and can reduce fertiliser costs.

Paul Withers of ADAS Bridgets, Matyr Worthy, Hants, claimed sludge applied to grassland could supply 150kg/ha (120 units/acre) of nitrogen, 100kg/ha (80 units/acre) of phosphate and 60kg/ha (48 units/acre) of sulphur. That was worth £80/ha (£32/acre).

Dr Withers added that nitrogen applications must be restricted to a years crop needs and when applied every three years most phosphate needs could be satisfied.

Sludge was best applied in spring to prevent water contamination and, on grassland, soil compaction must be avoided.

"Metals are a historic problem. Reduced metal contents and maximum application rates mean metal levels in most sludges are small. Spreading regulations state the permissible levels in soil. There is no effect on animal or human health."

Chris Rowland of the Water Services Association said more sewage sludge would be available for spreading on farm land after new EU legislation in 1998 which would prevent disposal at sea.

Sewage sludge could bring growers savings on fertiliser costs – ADAS.