The nitrogen and phosphorus concentrations of some pasture species in the Dichanthium-Eulalia Grasslands of North-West Queensland.

Abstract

The nitrogen and phosphorus concentrations of tops of the most common species at one site on the Dichanthium fecundum. Eulalla fulva grasslands of north-west Queensland were determined. The eight major grasses were sampled between 13 and 16 times over three consecutive dry seasons and three times during the growing season. Selected minor grasses and forbs were sampled on 30 occasions in both seasons over six years. Chrysopogon fallax and Iseilema spp. declined in phosphorus concentration during the dry season while the other major grasses remained constant. The nitrogen concentration of these two grasses and of Astrebla elymoides, A. squarrosa, D. fecundum and Sorghum australiense declined while that of E. fulra and Aristida latifolia was constant during the dry season. Both species of Astrebla had the highest concentrations of the two nutrients. The minor gasses had highest nitrogen and phosphorus concentrations in December at the start of the wet season and rapid declines in both nutrients occurred by March. These species were not intensively sampled during the dry season. The forbs had higher nutriant concentrations than grasses. The mean phosphorus concentration of major grasses in the dry season was highest (0.095%) in 1973 and lowest (0.065%) in 1974 following an abnormally wet summer. There was no difference in mean nitrogen concentration between years. It was 0.61% for the three dry seasons combined. The implications of these data for animal production are discussed.