Laboratory studies on losses of phosphorus, sulphur, and potassium from Te Kopuru sand

Abstract

Abstract Laboratory leaching studies on Te Kopuru sand, a mature podzol, showed considerable leaching of phosphorus, applied as superphosphate from two of the six samples examined. An inverse relation between leaching of phosphorus and phosphate fixation was found. IIence it is probable that a phosphate fixation test will indicate whether losses of phosphorus are likely to occur on a particular soil. Further studies revealed large losses of potassium and sulphur from a potassium chloride-superphosphate application. Leachin losses were much reduced when potassium and sulphur were applied as potassium bicarbonate plus elemental sulphur. Superphosphate accelerated losses of potassium from KCl, while basic slag did not. Very little potassium was leached when K was applied as K2HPO4. On this sand the use of a fertiliser, such as potassium phosphate, plus elemental sulphur, merits further study.