3 March 2000

More N leaching than from grass

ENVIRONMENTAL concerns exist over excess nitrogen in maize fields leaching into water courses and run-off.

There is more leaching in maize fields than in grass fields, and one way to reduce environmental concerns and improve the visual appearance of harvested maize fields is to undersow grass, said ADAS Bridgets Martin Froment.

Undersowing provides post-harvest ground cover so reducing surface run-off and mopping-up surplus nitrogen, enabling early grazing the following year. But successfully establishing a grass sward can be difficult, said Mr Froment.

The best approach is to apply atrazine as a band spray over maize and sow ryegrass between maize rows. Some producers had successfully established grass cover even after an overall atrazine spray.

Based on trial work at ADAS Bridgets, Mr Froment said the gap between applying atrazine and sowing ryegrass is important. "When too much atrazine is applied significant amounts remain in the soil and hold back ryegrass growth."