Utilising leaf number as an indicator for defoliation to restrict stem growth in rhodes grass (Chloris gayana) cv. Callide

Abstract

A plot experiment examined the yield response of a nitrogen-fertilised rhodes grass (Chloris gayana) sward to defoliation using the production of a set number of leaves after the last defoliation, as the indication, for defoliation harvesting. Two factors, defoliation frequency and nitrogen, fertiliser rate, were imposed on the rain-grown sward in south-east Queensland over 2 defoliation cycles. Defoliations occurred when an average of 2, 4, 6 and 8 leaves were produced on tillers, and the rates of nitrogen fertiliser were 150 and 300 kg/ha N. Total and leaf yields of rhodes grass were unaffected by defoliation frequency (P>0.05). Stem yield increased only once 4 leaves had been regrown; hence, leaf: stem ratio was highest at the 2- and 4-leaf defoliation intervals. This response was most pronounced when coupled with the higher rate of nitrogen fertiliser. The results suggest leaf number per tiller can be used as an indication of time to harvest rhodes grass pastures to limit the production of stem and increase the leaf: stem ratio. Further studies are required to examine this principle under grazing.