REGROWTH OF S24 RYEGRASS AND ITS RELATION TO YIELD MEASUREMENT OF GRAZED SWARDS

The re growth of S24 ryegrass (Lolium perenne L.) plants was studied during 4 days, following defoliation to stuhble heights of 2, 4, 6, 8, 10 and 12 cm. The weight of regrowth produced by plants cut to 6-cm stubhie heights and higher was equal to the weight increment of uncut plants above the same heights. During the 4 days the weight of the stubble segment between 0 and 2 cm decreased in plants cut to 2 or 4 cm, but was maintained or increased in plants cut to 6 cm or higher. Weights of the 2- to 4- to 6-cm stubble segments were just maintained at the lower cutting heights, but were increased by the same amount as in uncut plants at the highest cutting height. The percentage of water-soluble carbohydrates in all stubble segments decreased following defoliation, but the percentage of N did not change. Root weights were either maintained or increased, depending on the severity of cutting. In relation to grazing experiments, it is pointed out that where DM disappearance is taken as the difference hetween yield on a protected site and residue on a grazed site, too close cutting of the sample areas will give an overestimate of yield.