Seasonal production of Andropogon gayanus. I. Seasonal changes in yield components and chemical composition

Abstract

SUMMARYChanges in yield and quality of an Andropogon gayanus sward were traced throughout the 1964 wet season and part of the following dry season.Quality, in terms of crude-protein content, was highest at the beginning of the wet season, but yield increased to a maximum at the beginning of the dry season. Once flowering was completed in October, herbage quality fell to a very low level. It was concluded that the best time to cut for hay was in early October, at which time the crude-protein content showed a small but significant increase. Regrowth measurements taken in mid-November indicated the benefit of taking an early hay cut in July as a means of producing better quality hay at the end of the rains.During the early vegetative phase of growth leaf production was greater than stem production. Quality was high because the leaves contained a higher content of crudeprotein, calcium, phosphorus and carotene than the stems. During the reproductive stage of growth, comprising stem elongation in September culminating in anthesis in early October, quality was lower due to the high fibre content of the stems. The increase in crude-protein in early October, coincided with the expansion of new leaves on the flowering stems.It was concluded that throughout most of the latter part of the growing season A. gayanus did not provide adequate supplies of crude-protein, calcium and particularly phosphorus for normal cattle growth, especially after flowering was completed in late October.