, Volume 41, Issue 3, pp 541-547

The influence of phosphate deficiency on nitrification

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Summary

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.

This work forms part of a thesis approved by the University of London for the Ph.D. degree.
This work forms part of a thesis approved by the University of London for the Ph.D. degree.