Effect of phosphorus supply on three perennial Stylosanthes species in tropical Australia. I. Vegetative and reproductive growth

Abstract

Three perennial Stylosanthes species (S. scabra cv. Seca, S.guianenis cv. Schofield and S. viscosu CPI 34904) were grown on a soil of low acid-extractable (0.005 M H2SO4) P status (4 mg/kg) and supplied with either 0 (P0) or 50 kg P/ha (P50) to test their ability to grow under phosphorus-deficient conditions. Plants were grown in the field for two years (1978 and 1979), during which time dry matter yields of standing plant shoots, leaves, stems, inflorescence, podded seed and litter were recorded regularly.Perennial stylo, but especially Seca, grew well and produced high seed yields under conditions of low soil phosphorus. Based on their growth rates during the second wet season, tolerance to low phosphorus conditions decreased as follows: Seca> Schofield >CPI 34904. Two factors favouring Seca were its ability to allocate much of its dry matter to stem and its high yield of fine roots. Positive effects of phosphorus application occurred with leaf, stem, inflorescence, seed and litter yields, but were generally similar for the three species. There were large differences in dry matter distribution between species and little effect of applied phosphorus. Features were the high percentage of stem in Seca, and of inflorescence and seed in CPI 34904.