The residual value of superphosphate on a red-brown earth in South Australia

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Abstract
The residual value of superphosphate on a red-brown earth naturally deficient in phosphate has been determined by means of a field experiment. pot trials. and chemical extractions . In a field experiment on a site where 24½ cwt of superphosphate per acre had been previously applied over a period of 23 years, it was found that wheat. in a wheat-barley-fallow rotation. could be grown for 5 years before a clearly defined response developed to superphosphate currently applied at 11 lb (P1) or 22 lb (P2) phosphorus pentoxide (P2O5 ) per acre . Stubble-sown barley showed a response after the first year.