Abstract The relative effectiveness of superphosphate and equal weights of alternative phosphate fertilisers has been determined on two Waikato soil types over a period of 4 years. Nauru rock phosphate gave approximately half the yield increases obtained with superphosphate on Hamilton clay loam and one–third on Horotiu sandy loam. (The superphosphate responses were of the order of 16% on Hamilton clay loam and 32% on Horotiu sandy loam). North African phosphate gave yields similar to superphosphate on unlimed ground, but was less effective on limed ground, markedly so in the case of Horotiu sandy loam. Oxalic acid superphosphate gave inferior results on Hamilton clay loam, yielding in eight seasons significantly less than superphosphate. Serpentine superphosphate yielded slightly but consistently less than superphosphate. “Super compound” (75% superphosphate, 15% Nauru rock phosphate, 10% serpentine rock) gave similar results to superphosphate, exce...
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