Sward composition and output on grassland farms

Abstract

Abstract Records of grassland productivity were kept for 2 years on 136 lowland dairy farms and 131 lowland beef farms. The grassland on each farm was classified according to the proportion of sown (preferred) species. The farms were then ranked on this basis and divided into quarters: On dairy farms the lowest quarter had 31% sown species and utilized metabolizable energy (UME) output from grass of 40.8 GJ ha −1 , whereas the highest quarter had 70% sown species and UME output of 45.6 GJ ha −1 . Dairy farmers in the lowest quarter used least fertilizer N and differences in output were no greater than would be expected from differences in N input. On beef farms the lowest quarter had 28% sown species and UME output of 32.3 GJ ha −1 , and the highest quarter had 63% sown species and UME output of 45.9 GJ ha −1 On these farms differences in fertilizer N could not completely account for differences in output. It is concluded that on beef farms botanical composition of grassland is a good indicator of its productivity but is not necessarily a prime cause of differences in output. On dairy farms there is little evidence of a direct benefit resulting from a high proportion of sown species. On such farms the need for deliberate manipulation of the botanical composition of grassland by reseeding or chemical means is questioned.