Effect of Shading on the Regrowth of Lolium perenne Swards in the Field

Abstract

Simulated swards of Lolium perenne cv. S.23 growing in the field were shaded at various stages of regrowth during August and September, when insolation was most likely to be limiting. Reduction of ambient illumination to 50 per cent for periods up to 24 days had little effect on the current production of herbage (mainly leaf blade), which progressed at the expense of root and stubble growth. After defoliation, however, previously shaded swards transferred to full light regrew relatively slowly. Leaf area and leaf extension were increased by shading, but leaf appearance rates were only slightly affected. Shading decreased tiller densi ties, and hence stubble yields, but did not affect mean tiller weights. The dangers of relating herbage yield to current rates of insolation and photosynthesis, and the relevance of these findings to other grass varieties are discussed.