Nitrogen in temperate crop and pasture plants

Abstract

Nitrogen concentrations were determined in the tops of 24 annual crop and pasture varieties grown together in ungrazed plots on a lateritic gravelly sand at Gidgegannup, W.A., and sampled at three stages during growth and at maturity. All legumes had higher nitrogen concentrations in the tops than all non-legumes, but considerable variation was evident within each group. Among pasture legumes, Ornithopus compressus and O. sativus had the highest concentrations, especially towards maturity, and Trifolium subterraneum cv. Yarloop and Clare the lowest. Nitrogen concentrations in all Lupinus spp. fell rapidly towards maturity, and they were unique in suffering substantial net nitrogen losses from the tops. The herb Erodium botrys grew better and took up more nitrogen under conditions of deficiency than did the grasses. Its nitrogen concentration was nevertheless very low. Among the grasses, Bromus rigidus consistently had the highest nitrogen concentration and Lolium rigidum the lowest. There was some evidence among non-legumes of a correlation between high nitrogen concentrations and/or total uptake and observed adaptation to sandy soils. The superior adaptation of legumes in the experimental environment was demonstrated. It is suggested that crop legumes could make a more important agronomic contribution than hitherto in this and similar environments.