The influence of phosphate deficiency on nitrification
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- Purchase, B.S. Plant Soil (1974) 41: 541. doi:10.1007/BF02185815
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Ammonium sulphate applied to savanna grassland stimulated nitriteoxidizers in some plots but not in others. Extracts from the contrasting soils differed in suitability as growth media for nitrite-oxidizers. This difference could be eliminated by adding KH2PO4 or Na2HPO4 to the extracts. The concentration of available P was highest in soils where nitrite-oxidizers had responded to (NH4)2SO4.
Various soils were mixed with (NH4)2SO4 and then incubated. In those containing less than 6 μg/g of available P, nitrate accumulation between days 4 and 11 was correlated with the concentration of available P. Between days 11 and 31 there was no such correlation.
When a mixture of ammonia- and nitrite-oxidizers was grown in media containing various concentrations of P, nitrite accumulation was abnormally high where the P concentration was low.
It is concluded that nitrite-oxidizers are more sensitive to P deficiency than are ammonia-oxidizers and that P deficiency is sufficiently severe in many Rhodesian soils to restrict the growth rate of nitrite-oxidizers, thereby restricting their ability to compete for nitrogen.