The effects of season, stage of growth, and soil type on the chemical composition of grasses in the Queensland “wet belt ”

Abstract

Three cultivated perennial grasses, namely Para grass (Brachiaria purpurascens [Brachiaria mutica], Raddi), molasses grass (Melinis minutiflora, Beauv.) and Guinea grass (Panicum maximum, Jacq.) and 2 adventitious indigenous perennials, namely sour grass (Paspalum canjugatum, Berg.) and Russell River grass (Paspalum paniculatum, L.) were examined. The material was collected from 14 paddocks, at the ' pre-wet ' period, ' mid-wet ' period, ' late-wet ' period and ' mid-dry ' period of the season. Detailed data are given for the percentages of the proximate constituents as well as for CaO and P2O3. The average annual rainfall in the area is 150 inches, 75 per cent of which falls in the first 6 months of the year. The relative humidity is 75 to 85 per cent, and the mean maximum and minimum temperatures for the year are 83 and 65° F. Only the leafy parts of the grasses, such as are eaten by cattle, were taken for analysis. The dry matter content of the first 3 grasses was higher in long than in short grass and was higher in the dry season than at the end of the wet season for Para and molasses grass. Crude protein rose with the progress of the wet season and then fell sharply during the dry period; the Ca content usually rose in the dry season. There was no marked seasonal variation in P content. Certain other variations were noted. There was a significant correlation between the protein and P contents of Para grass during the whole of the wet season, December to July, but not in the dry period. Para grass showed a general superiority over the other grasses studied in respect of protein, fibre, and Ca and P contents. There was an indication that the P content of the herbage might be inadequate in drought periods.-W. Godden.