SOLUBILIZATION OF PHOSPHATE BY RICE PLANTS GROWING IN REDUCED SOIL - PREDICTION OF THE AMOUNT SOLUBILIZED AND THE RESULTANT INCREASE IN UPTAKE

被引:46
作者
KIRK, GJD
SALEQUE, MA
机构
[1] International Rice Research Institute, Manila, 1099
关键词
D O I
10.1111/j.1365-2389.1995.tb01833.x
中图分类号
S15 [土壤学];
学科分类号
0903 ; 090301 ;
摘要
Previous work has shown that rice plants growing in reduced soil are able to solubilize P by inducing an acidification in the rhizosphere through H+ produced in Fe2+ oxidation by root-released O-2, and by the direct release of H+ from the roots to balance excess intake of cations over anions. In this paper, equations for the diffusion and interaction of P and acid in soil are developed to predict the resultant increase in P uptake by the roots. Good agreement was obtained between the profiles of P and pH in the rhizosphere measured in the previous experiments, and those predicted using the equations with independently measured parameter values. The equations showed that solubilization accounted for over 80% of the P taken up. Measurements of the solubilization parameters in a range of reduced rice soils showed that H+ addition increased the quantity of P that could be desorbed per unit weight of soil and the concentration of P in solution, in all the soils tested. The quantity of P solubilized per unit H+ added at a given solution P concentration varied about 50-fold between soils, with a median of 11.9 mmol P per mol H+. The native soil solution P concentration varied 50-fold (median=0.91 mu M) and the soil pP buffer power (the quantity of P desorbed per unit decrease in -log of the P concentration in solution) varied 100-fold (median = 0.36 mmol kg(-1) pP(-1)); the soil pH buffer power varied 7-fold (median = 0.075 mmol kg(-1) pH(-1)). Calculations indicated that, in most of the soils tested, rice plants would depend upon solubilization for the bulk of their P.
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页码:247 / 255
页数:9
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