Growth and nitrogen fixation by subterranean clover in response to inoculation,molybdenum application and soil amendment with lime

Liming an acid soil increased the yield and N content of subterranean clover in both field and glasshouse experiments. Application of Mo increased the N concentration of field-grown subterranean clover which corresponded with observed colour and growth differences, but did not change C₂H₂ reduction activity. Herbage Mo was not increased by liming, suggesting an absolute deficiency of Mo in these acid soils. In the glasshouse liming increased nodulation which increased the amount of N₂ fixed but the lime had no direct effect on nitrogenase activity as measured by C₂H₂ reduction. In the field both inoculation and lime application increased soil populations of R. trifolii, but clover yield was greater with liming alone than with inoculation alone, indicating the sensitivity of the host plant to soil acidity.