Regrowth characteristics of an S. 23 perennial ryegrass sward defoliated at early stages of reproductive development

Abstract

Summary Patterns of stem development in late spring/summer regrowths after initial cuts at three growth stages are described. The stages at which the initial cuts were taken were: ( a ) before stem apices were raised to defoliation level (5 cm), ( b ) two weeks later when the apices of about 90% of the stem tillers were raised above this height, and ( c ) four weeks after ( a ), when the apices of all stem tillers were raised well above cutting height. Following an initial cut at stage ( a ) stem development was quickly resumed, the most advanced tillers being devoid of leaf blades. After initial cuts at the later stages there was virtually no stem development until after the fourth week of regrowth. The greater proportion of stem tillers in the earlier regrowth was not reflected in reduced digestibility during the first six weeks from cutting. Reproductive (apical) development was generally weak in tillers in which stems developed in midsummer (after cutting at stages b and c ); at least two-thirds of these tillers were indeterminate. The significance of the distinct batch of stem tillers developing in spring is discussed, and the data are also considered in relation to (i) avoiding stemmy regrowths in spring, (ii) stem development and herbage quality, and (iii) summer stem extension and the perennation of the sward.