Abstract

Plants of Lolium perenne, set up in a minisward in a glasshouse, were redefoliated at 3, 6 or 3 plus 6 days after defoliation at 2 or 5 cm stubble height. Regrowth, water soluble carbohydrate (WSC) content, and tillers per plant and tiller weight were measured. At the extreme, 70% of plants died when they were defoliated at 2 cm stubble height and redefoliated at 3 plus 6 days later. The mean total regrowth at the 3 leaves per tiller stage (and including the DM yield at each redefoliation) of the surviving plants was 4% of plants not defoliated and cut to the same stubble height. Redefoliation had a less marked effect on plants cut at 5 cm stubble height, reducing total regrowth by 55, 78 and 95%, for plants redefoliated at 3, 6 or 3 plus 6 days, respectively. There was a very significant relationship between tillers per plant and stubble WSC (mglplant) (Adj r2 = 0.90; P = 0.001) or stubble DM (g/plant) (Adj r2 = 0.89; P = 0.001) at the 1+ a leaf stage of regrowth on DM yields at the 3 stage of the regrowth cycle. These results confirm the dramatic effect of redefoliation on regrowth of ryegrass plants, and support the recommendation that grazing duration in the field be restricted to less than 3 days to prevent stock regrazing new leaf.