STRATEGIES TO DECREASE NITRATE LEACHING IN THE BRIMSTONE FARM EXPERIMENT, OXFORDSHIRE, UK, 1988-93 - THE EFFECT OF STRAW INCORPORATION

Nitrate lass in drainwater and cultivated layer flow was measured over 5 years on two pairs of hydrologically isolated plots, one pair with cereal straw incorporated for 4 years and burnt in the fifth, and the other with straw burnt in all 5 years. Although straw incorporation de creased nitrate leaching and probably decreased net mineralization of soil organic matter in the first winter, these effects were apparently diminished or even reversed in later winters, and the straw had no be nefit on cereal yields or N-uptakes. The results suggest that the pres ent practice on UK farms of regularly incorporating cereal straw is un likely to decrease nitrate losses and in the long term may increase th em, especially on clay soils and in wet winters after long dry periods . On clay soils it is also unlikely to increase crop yields in the sho rt or medium term.