The effect of repeated defoliation to three different levels on root growth of five pasture species

Abstract

Defoliating young plants of perennial ryegrass, cocksfoot, timothy, white clover, and red clover to 25 mm, 50 mm, or 100 mm above the base of the shoot every second day depressed root elongation in all cases. The 25 mm treatment caused complete or nearly complete cessation of root elongation in all species except white clover, in which the level was reduced to approximately five percent of that of undefoliated plants. The level of root elongation in the three grasses was related to the percentage of leaf lamina remaining after the initial defoliation, but this relationship did not hold in the two clovers. The percentage of roots which died as a result of defoliation was greater in perennial ryegrass than in red or white clovers, although the percentage leaf lamina remaining was higher in the ryegrass. Similarly, cocksfoot, with a greater percentage of leaf lamina remaining, had a greater percentage root death than did the other two grasses. © 1973 Taylor & Francis Group, LLC.