The effect of evaporative demand on the growth of well-watered kikuyu

Abstract

A study was made of the effect of evaporative demand (potential evapotranspiration, E t) on the growth of heavily fertilized and well-watered kikuyu pasture. Mean weekly growth rates on an irrigated pasture, adjusted for differences in temperature during the various growth periods, declined significantly when the mean E t increased above 3.5 mm day −1. Using growth rates at lower E t as a no-stress control, the maximum reduction in growth rate (57%) occurred at the highest E t (5.0–5.8 mm day −1). When frequent leaf wetting was used to modify the possible effects of evaporative demand on the internal water status of the plant, the growth rate still declined with increasing E t, but to a lesser extent than on irrigated pasture. The leaf wetting was done at 20-min intervals and evidently this interval was too long to fully ameliorate the evaporative demand effect when mean E t exceeded 4.5 mm day −1. It was concluded that the growth of kikuyu is sensitive to evaporative demand even on wet soil and that cloudy periods enhance growth by reducing E t.