Competition of Erodium botrys and Trifolium subterraneum for Phosphorus

Abstract

Differential response to phosphorus by broadleaf filaree (Erodium botrys) and subclover (Trifolium subterraneum) in competition was studied in a phosphorus-deficient soil and in sand culture in pots. The data show the superior competitive ability of filaree, a resident annual forb, over subclover, an introduced annual legume, both at high fertility levels including abundant nitrogen, and in soils low in N, P, and S. Under high fertility, the rapid growth of filaree enables it to develop considerable leaf area and interfere with the light reception of subclover. Since most of the range soils in California are nitrogen-deficient, however, subclover, with its ability to fix atmospheric nitrogen, is able, when P and S are adequate, to outcompete filaree and assume a dominant role. In order to maintain a proper balance among grasses, legumes, and filaree, most California range soils must be topdressed periodically with superphosphate; otherwise, subclover soon becomes subordinate or disappears.