The effects of some pasture species on soil structure

Abstract

The effect of pure stands of six pasture species in restoring the structure of a red-brown clay loam at Canberra, A.C.T., that had been under cultivation for twelve years, was measured each spring for four years. The species used were Lolium perenne L., L. rigidum Gaud., Medicago sativa L., Phalaris tuberosa L., Trifolium pratense L. and T. subterraneum L. There was no measurable effect or difference between any of the pasture species in restoring structure during the five month establishment period, but thereafter soil aggregation improved, although after four seasons it was still substantially less than under adjacent virgin pasture. Differences between species and between years were variable and the variation appeared greater with legumes than with grasses. Soil aggregation was more closely correlated with the macro-organic content of the soil during the preceding year than that in the same year. The clay plus silt content of the water stable aggregates increased each year on all treatments and on the controls.