The value of Nauru rock phosphate as a source of phosphorus for some tropical pasture legumes

Abstract

Using soils known to be grossly deficient in phosphorus, and with a basal dressing of sulphur (and other deficient nutrients) plants were grown in pots and in the field with single superphosphate or Nauru rock phosphate. The plants fell into two groups, those that gave moderate yield responses to rock phosphate as compared with superphosphate (Lotononis bainesii, Stylosanthes guyanensis, Centrosema pubescens, Indigofera spicata, and Medicago sativa) and those whose response to rock phosphate was poor (Desmodium uncinatum and Phaseolus lathyroides). In no case was the response to rock phosphate as good as that to superphosphate, even when twice as much phosphorus, in the form of rock phosphate, was applied. The residual value of rock phosphate was low with Desmodium, high with Lotononis, but never as high as that of superphosphate.