The Effect of Fertilizer Nitrogen and White Clover on Herbage Production

The effect of a range of N rates on herbage production from grass/white‐clover and grass swards was investigated in two long‐term grazed experiments. The mixed sward yielded more than the grass swards over the range of fertilizer rates tested which were 0–120 lb N/ac (134.5 kg/ha), but the response of the mixed sward to fertilizer N was less than that of tbe grass sward. Tbis was due to the direct and indirect effect of clover, which was considerable with no fertilizer N but decreased witb increasing rates of application. However, clover was not completely suppressed by N at eitber site and contributed to berhage yields at all N rates. Rate and time of N application and the amount of clover in tbe sward affected tbe seasonal distribution of DM yields. The mid‐season decline was less marked at bigb‐ tban at intermediate‐levels of N supply.