The performance of a white clover based dairy system in comparison with a grass/fertiliser-N system. II. Animal production, economics and environment

The performance of a white clover based dairy system in comparison with a g rass/fertiliser-N system was studied during three years. Both systems had 5 9 cows, plus young stock, on an area of 40.6 ha for grass/clover and 34.4 h a for grass/fertiliser-N During the grazing season, the cows in both groups were supplemented with 3 .5 kg concentrates day(-1). The daily Fat and Protein Corrected Milk (FPCM) production was 25.7 and 26.5 kg cow(-1) for grass/fertiliser-N and grass/c lover, respectively. The difference in milk production occurred from July o nwards. Despite preventive measures in the grass/clover system, bloat occur red several times between August and October. During the housing season, co ws received ad libitum grass or grass/clover silage with 6 kg concentrates cow(-1) day(-1). Although the intake of grass/clover silage was consistentl y higher, there were no differences in milk production. The grass/clover system had a lower N surplus, but this was related to the lower intensity of the system. The overall N utilisation was 25% in both sy stems. The average nitrate concentration in drain water, measured on a sele ction of fields, was 26 and 28 mg l(-1) for grass/fertiliser-N and grass/cl over, respectively. The nitrate concentrations in drain water from grass/cl over fields were positively related with the clover content in the sward. T he energy use of the grass/clover system was 15% lower than that of the gra ss/fertiliser-N system, with the fertiliser use as the main source of diffe rence. Compared to the grass/fertiliser-N system, the gross margin per cow was slightly higher for grass/clover, but the gross margin per ha was 10% l ower for grass/clover. Considering agronomic and environmental aspects only, white clover based da iry systems are a viable option for the future, but from a financial Viewpo int the use of white clover will be restricted to systems which produce app roximately 12 t FPCM ha(-1) year(-1) or less.