Factors affecting the leaf extension rate of perennial ryegrass in spring

Abstract

AbstractThe effects of soil temperature and other factors on the early spring growth of perennial ryegrass (Lolium perenne) swards were studied in 1983, 1984 and 1985. Leaf extension was used as the measure of growth and soil temperature was recorded at 10 cm depth below bare ground. Measurements were taken before the first nitrogen dressing had been applied each spring on swards that had received annual dressings of 0, 200 or 400 kg N ha‐1 since 1982.On the pooled data temperature alone accounted for 604% of the variation in leaf extension rate, with an average increase of 0·4 mm d‐1 for each 1°C increase in temperature over the range studied. Considering the data for each year separately did not greatly improve the correlation but did indicate that leaves extended more rapidly in 1985 for each degree increase in temperature whereas the smallest response was recorded in 1984. A better correlation was achieved by grouping data according to the nitrogen rates previously applied to plots and there was evidence of residual effets of this nitrogen. It seems likely that the differences between years can be explained in terms of differences in radiation and other environmental parameters over the measurement period, whereas the effects of previously applied nitrogen may be more closely related to physiological changes in the sward.