The effect of defoliation on inflorescence production, seed yield and hard-seededness in swards of subterranean clover

Abstract

Swards of three strains of subterranean clover (Seaton Park, Yarloop, Midland B) were subjected to a range of defoliation treatments. In all strains, cutting at weekly intervals at a height of 1.5–2 cm from 1 month after sowing until the onset of flowering led to a slight delay in flower initiation but the time of flowering was little affected. The rate of inflorescence production, however, was always increased, as was the total number of inflorescences produced by the end of flowering. In particular, seed yields were increased by at least 30% compared with uncut controls. This effect was attributable partly to increased inflorescence numbers and partly to increases in other yield components as a consequence of the burial of a large proportion of burrs. Cutting increased the initial level of hard-seededness in Seaton Park and Yarloop; in addition the rate of breakdown of hard-seededness in all strains was slower in seed from the defoliated swards. When cutting was continued until midway through flowering (with the cutting height progressively raised) the seed yield in Yarloop and especially in Midland B was much lower than that obtained when cutting was stopped at the beginning of flowering; but in Seaton Park there was no reduction. With further cutting-until the end of flowering-seed yields were less than when cutting was stopped midway through flowering. Extending cutting into the flowering period (compared with cutting only until the onset of flowering) resulted in a decline in the initial level of hard-seededness and an increase in the rate of breakdown of hard-seededness in Midland B but had little effect in Yarloop or Seaton Park.

Seed Bank Dynamics in a Mediterranean Grassland

“…An estimate of the average number of seeds set per plant showed that there was a tendency for all species to set more seeds per plant under high stocking rate than under low stocking rate (Table 1). A possible explanation could be that defoliation increased seed production probably because of increased branching, as reported, for example, in Trifolium subterraneum (Rossiter 1961(Rossiter , 1972Collins 1978).…”

Evaluation of clovers in dry hill country 4. Components of subterranean clover regeneration at Whatawhata, New Zealand

“…Flowering time, physiological seed dormancy, and hardseededness are important plant factors (Donald 1960;Rossiter 1966;Collins et al 1976). However, their relative importance mayalterdepending on summerrainfall, grazing management, and plant competition (Quinlivan 1965;Ragon 1974;Collins 1978).…”

Effect of timing of forage conservation on forage yield and quality, seed yield and seedling regeneration of four subterranean clover (Trifolium subterraneum) cultivars

“…Defoliation once flowering has commenced is lower, with in vitro digestibility declining to 42-50% and crude known to reduce seed set with reductions becoming greater the protein (CP) to 9% (Mulholland et al 1996;Ru and Fortune later and more severe the defoliation (Collins 1978;Conlan 2001;Norman et al 2005). Rainfall over summer further et al 1994;Stockdale 2005).…”

“…defoliating before flowering commences on seed set is most The excess of herbage in spring is also a problem in pastures likely a result of increased branching of the runners and locked up for clover seed harvesting as the residues interfere promotion of burr burial (Rossiter 1961;Collins 1978; Collins with the recovery of the clover burr containing the seed. et al 1983).…”