The influence of temperature and soil water potential on the leaf extension rate of perennial ryegrass in Northern Ireland

Abstract

Summary: The rate of leaf extension in swards of the perennial ryegrass cv. Perma was monitored continuously from March 1976 to September 1977 in Northern Ireland. In this period air temperature and soil water potential were shown to be closely correlated with leaf extension rate. Simple linear expressions are shown to adequately describe the relationship between temperature and leaf extension rate when the year is divided into a winter phase, in which sward growth is very slow, and the remainder of the year in which temperature is high enough to allow significant sward production. Leaf extension growth occurred at all temperatures above freezing point. Soil water potentials of 0·15 MPa are shown to be capable of significantly reducing leaf extension rate. However, the occurrence of such soil water potentials are sufficiently rare in Northern Ireland as to permit prediction of leaf extension rates in perennial ryegrass from simple daily temperature records.