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Relationships of yields of maize and cotton, and their response to phosphate fertilizer, with soil phosphate potentials in Tanzania

Published online by Cambridge University Press:  27 March 2009

T. M. Addiscott
T. M. Addiscott
Affiliation:
Western Research Centre, Ukiriguru, Mwanza, Tanzania*
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Summary

Yields of maize and cotton given N, and sometimes K but no P, were related to equilibrium values of the monocalcium phosphate potential (½pCa+pH2PO4)eq', at which P is neither lost nor gained by the soil. The responses to phosphate fertilizer were not clearly related to phosphate potentials though small responses at large values of (½pCa+pH2PO4)eq were sometimes explained by very small values of δI/δQ (the rate of change of ½pCa+pH2PO4with change in the amount of P on the soil) or by soil reaction. In only one set of maize experiments, response to P was related to δI/δQ. (½pCa+pH2PO4)0 and (pH2PO4)0', determined without adding P to the solution, were equally useful and both were just as well related to yields without P as (½pCa+pH2PO4)eq' (pH2PO4)0 appeared more useful than the logarithm of the total P concentration measured without added P. It wa not necessary to find the equilibrium phosphate potential, or to measure Ca concentration, but correcting the phosphate concentration for pH (so that only H2PO4-ions were taken into account)was worth while.

Type
Research Article
Information
The Journal of Agricultural Science , Volume 72 , Issue 3 , June 1969 , pp. 401 - 403
Copyright
Copyright © Cambridge University Press 1969

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References

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