8 March 2002

NVZ rules are set to hit farmers hard

USING maize areas for slurry disposal and applying manure to boost soil potash levels are the key areas where nitrate vulnerable zone (NVZ) rules will hit maize growers.

Large quantities of organic manures are often applied before maize is sown, said LEAF managing director Caroline Drummond at the MGA conference. "But applications must not exceed 250kg/ha (200 units/acre) of total nitrogen within the rules.

"In addition, maize grown continuously in the same area can lead to large amounts of nitrogen and phosphate building up in the soil. This increases the risk of nitrate and phosphate pollution of water."

Rotating maize with other crops is one solution to avoid this build up of soil nutrients. But care is still needed to avoid excess nutrient inputs as manure and fertiliser.

One key part of managing slurry nitrogen inputs is knowing the slurrys nitrogen content, said MGA agronomist Simon Draper. "Measuring nitrogen content can make up to 30% difference on the area needed to dispose of slurry, compared with book values."

Another problem faced by growers is confusion about the rules, said Environment Agency adviser Richard Smith. "Dung from weeping walls is exempt from the closed period, while the effluent is not and some units dont have the storage," he explained.