Influence of defoliation on some aspects of regrowth and senescence of Persian clover herbage grown in pots

Abstract

This experiment investigated the effects of defoliation management of Persian clover (Trifolium resupinatum) on herbage production, and in particular, regrowth and losses of production due to senescence. Three heights of defoliation of Persian clover (0, 5, 10 cm above soil level) were superimposed on 3 frequencies of defoliation (4, 6, 12 weeks between harvests until early October; 3, 4.5, 9 weeks subsequently) in a completely randomised pot experiment with 3 replicates. Defoliation management had a large effect on yield of harvested herbage, in agreement with earlier studies with Persian clover in mixed swards or as a monoculture in the field. The amount of herbage that grew below defoliation height and subsequently died was 0-21% of the total herbage grown. The amount of dead and dying matter in herbage above and below defoliation height increased as both defoliation height and interval increased. This represented up to 61% of the total herbage grown. Aspects of regrowth (leaf area, petiole number, petiole extension rate, yield of herbage during growth, biomass of root relative to shoot) were measured. Except at very long defoliation intervals, vegetative growth of Persian clover herbage was positively associated with all of the above variables. The pattern of change with time in the rate of green herbage accumulation following defoliation reflected the balance between changes in the growth of new plant tissue and the loss of mature tissue to senescence and decomposition.