RESPONSE OF GRASSLAND TO NITROGENOUS FERTILIZER IN THE WEST OF ENGLAND

Extensive replicated plot experiments were carried out at Henley Manor Farm from 1956–1961 to obtain accurate measurements of herbage production and response to nitrogenous fertilizers under West of England conditions. 356 plots were used; use of the herbage by both cutting and grazing was studied. The principal results are: Grass/ clover swards (containing approx. 35% clover) grown without nitrogenous fertilizer averaged 75 cwt dry matter per acre per annum. Application of nitro-chalk to initially grass/clover swards reduced the clover content of the herbage. About 133 lb N/annum was required by an all-grass sward to equal the production of a grass/clover sward without N. Attempts to increase production of grass/clover swards by using N for early growth and relying on clover for mid-season growth were unsuccessful in 2 out of 3 years. Swards (initially grass/clover) gave significant increases in total dry-matter production from regular use of the lowest level of N (26.0 or 34.7 lb N/acre/cut or graze) in 44 out of 49 cases. Extremely high yields were obtained from the heaviest use of N (104.2 lb N/acre/silage cut). 52.1 lb N/acre/cut or graze was the optimum rate of application on ail-grass and grass/clover swards. Up to about 350 lb N/acre/annum the dosage-response curve was very nearly straight for all-grass and grass/clover swards. On the grazed plots herbage left ungrazed amounted on average to only 6% of the total. The health of all stock on the high nitrogen plots (as well as all others) was excellent.