N.J. BRANDON and R.A. DATE

CSIRO Tropical Agriculture, St Lucia, Queensland, Australia

Abstract

Nutrient-omission and addition trials, in pots, were used to determine whether nutrient deficiencies were responsible for stunting and chlorosis in stands of Desmanthus virgatus growing in a black earth soil at Gayndah in south-east Queensland. After 11-weeks growth, omission of S or Mo, relative to a complete treatment, reduced yield by 55% and 42%, respectively, in inoculated plants and 92% and 14%, respectively, in N-fertilised plants. Omission of P, Cu or Mn reduced growth of inoculated plants by 8–24% but had no significant effect on yield of N-fertilised plants.
The combined addition of P, S, Mo, K, Ca, Mg, Zn, Cu, Mn and B to inoculated plants almost doubled yield of plant tops 11 weeks after planting, but there was no significant yield response when P, S or Mo was applied alone.
The results suggest that S, Mo and possibly P, Cu and Mn may contribute to the development of chlorosis and low yield of inoculated desmanthus at Gayndah. A critical S concentration in leaf tissue of 0.20% was determined in an S-rate trial.