The effect of tree leaf litter on sward botanical composition and growth

Abstract

Freshly fallen leaf litter of sycamore and hybrid larch was applied in November to a variety of different swards including perennial ryegrass-white clover swards and white clover monocultures. Sycamore litter reduced ryegrass in the mixed sward and clover in the monoculture the following February. Although clover had returned to control levels by March, ryegrass remained suppressed. Herbage weight in the mixed sward was reduced as was clover stolon length in the monocultures. The effect appeared to be due to a smothering of the sward. In contrast larch litter had much less effect on the sward with only temporary reductions in grass and clover. In addition there was a general increase in herbage weight and clover stolon length in larch treatments. This apparent stimulation of the sward by larch litter does not appear to be a result of nutrients leaching from the decomposing litter. Larch litter made net gains in N, P and K whilst sycamore litter exhibited a net loss of P and K. It is suggested that differences seen between the two litter treatments are as a result of different leaf form: larch needles by settling at ground level did not smother the sward to the same extent as the broadleaved sycamore and so may have afforded some insulatory protection for the overwintering stolons.