Effects of defoliation management on the productivity of an irrigated Persian clover sward

Abstract

A field experiment investigated the effects of frequency and height of defoliation on the productivity of an irrigated Persian clover (Trifolium resupinatum) sward. Combinations of 4 intervals of harvest (3, 6, 9, 12 weeks) and 2 heights of defoliation (to ground level or 5 cm above ground level) were used in a randomised block experiment, with 2 additional treatments of 4 and 18 weeks between harvests defoliated to ground level. Total herbage accumulation ranged from 8.46 to 13.90 t DM/ha and varied according to defoliation management. Except for the very short defoliation intervals, harvesting to 5 cm was less productive than harvesting to ground level. The effects of leaf area index, herbage yield, and infection with leaf fungal disease on growth rates were assessed. Leaf area had a positive effect, and fungal disease a negative effect, on herbage growth rates, while maximum growth rates in autumn-winter were achieved when herbage yield reached about 2.0 t DM/ha. Dead matter accumulation increased with the interval between harvests, and weeds invaded the plots at both the shortest and longest defoliation intervals. The quality of seed produced (seed weight) was not influenced by defoliation treatment (0.1112 g/100 seeds, on average). Defoliation interval was positively related to number of inflorescences and quantity of seed set, but height of defoliation did not significantly affect these variables. It was concluded that the optimum interval of harvest was 6-9 weeks. Height of defoliation had only minor effects, due to the small difference in residual dry matter between the treatments.