Nutrient responses of an indigenous Poa tussock and Lolium perenne L. grown separately and together in pot culture

In the first of two glasshouse experiments, Lolium perenne and Poa labillardieriwere grown separately with three levels of nitrogen, four levels of phosphorus, four levels of sulphur and two levels of potassium in all factorial combinations. There were no major differences in the relative responses of the two species. The root/shoot ratio of Lolium was twice that of Poa at the final harvest. Uptake of sulphur was higher in Lolium at high levels of applied sulphur. In the second experiment, Lolium and Poa were grown in pure and mixed culture at five levels of applied nutrients. Grown alone the yields of both grasses were similar to the first experiment but in mixed cultures the shoot yields of Poa were reduced to 20% of those in pure culture. The success of Lolium was attributed to its larger seed and more rapid early growth. Normally Poa increases in size and numbers to dominate natural grasslands if superphosphate fertilizer is applied and white clover develops. The results suggest that the dominance of Poa in these grasslands could be restricted by establishing a vigorous stand of Lolium at the beginning of arable pasture improvement.