The effect of grassland renovation and break up on nitrogen losses.

This paper focuses on a series of experiments we conducted over an 8-year period (1999 till now) on sandy soils concerning the renovation of grassland and its break up for arable use. Our main interest was the effect of such break up or renewal on the environment, namely nitrate leaching, soil mineral nitrogen (SMN) and related soil processes. Among the factors we considered were: the influence of season of renewal, of previous N management (including clover), of N fertilization for the new sward, and of technique of renovation; the influence of the crop and N management following a grassland break up, and of soil characteristics on SMN and nitrate leaching. We also compared permanent grassland with long intervals of renewal, or break up with regular forage farming using Italian ryegrass and maize. Our findings suggest that spring renovation is preferable to autumn renewal, and actual N application should be reduced in order to minimize nitrate losses. After break up for arable use, spring barley followed by a catch crop was favourable to the cultivation of silage maize in storing mineralized N and controlling N leaching.