Long-term effects of fertilizers on herbage production: I. Yields and botanical composition

In a factorial experiment on a mixed grass/clover sward, continued over 13 years, D.M. yields were strongly affected by N and K, which showed a marked interaction. P had very little effect on yield. There was evidence of a depressing effect on yield of continued application of KC1 at low rates of N input: this is thought to be due to excess Cl. It may be associated with the effect of Cl on clover growth, since it did not occur in predominantly grassy swards heavily dressed with N, in spite of high Cl content in the herbage. The botanical composition of the herbage was strongly affected by the fertilizer treatments.