Legumes as suppliers of nitrogen to pasture.

Nitrogen losses ranging between 0, 16 and 0, 26 kg/ha/day may occur direct from the soil of grazed legume pastures while removal of animal products from the system represents a major loss of N from the system in the form of protein. On a global basis it has been estimated that annully 200 million tons of N are fixed abiologically (e.g. by lightning) whereas 175 million tons are fixed biologically. Estimates for the fixation of N by clover in a grass/clover mixture range from 100 to 200 kg N/ha/year. Under certain specific circumstances N fertilisation of legume/grass pastures may be advantageous but generally nodule formation and N fixation is depressed by N fertilisation. In many cases failure of legumes to perform adequately in pastures has been due to poor inoculants but strict quality control now ensures the availability of more reliable inoculants in South Africa.Keywords: availability; biological fixation; formation; legumes; lightning; nitrogen; pasture; pastures; protein; quality; range; south afric