PERSISTENCE AND COLONIZATION OF GAPS IN SOWN SWARDS OF GRASS AND CLOVER UNDER DIFFERENT SWARD MANAGEMENTS

The effects of extensive sward management and patch size on the persis tence and colonization of gaps in sown swards was examined by creating gaps of five different sizes (2.3, 7, 10, 14 and 19 cm in diameter) i n four different award treatments: a fertilized sward grazed to 4 cm, i.e. relatively intensive management, and three extensively managed un fertilized swards, which were not grazed or grazed to 4 cm or 8 cm. Th e swards were originally sown with ryegrass (Lolium perenne L.) and wh ite clover (Trifolium repens L.), but had developed differences in spe cies composition as a result of the management treatments imposed 2 ye ars before and during the experiment. Light quality measurements, i.e. red-far red (R/FR) ratio, were used to determine when the light envir onment in the gaps no longer differed from that in control, uncut patc hes and this was used as an estimate of gap persistence. Persistence o f gaps depended on both sward management and gap size. Gaps disappeare d most rapidly in the ungrazed sward and fertilized 4-cm sward, and mo st slowly in the unfertilized 8-cm award. Small gaps persisted for up to 2 weeks in all but 8-cm swards, whereas larger gaps were estimated to persist for up to 20-25 weeks in unfertilized, grazed swards. There was no evidence that the number of grass or dicotyledonous species in creased in the gaps compared with the control areas. There were signif icant positive linear relationships between the vegetation that develo ped in gaps and that in the control, uncut patches, reflecting the dif ferent species composition of the established sward of the grazed (gra ss-dominant) and ungrazed (Ranunculus repens-dominant) treatments. For total grass dry matter and tiller numbers, as well as L, perenne till er numbers, there was a small, but significant, effect of both patch s ize and sward management on the slopes of the regressions between the controls and gaps. The results are discussed in relation to the potent ial for species composition of sown swards to change as a result of ga p creation.