RESIDUAL EFFECT OF PHOSPHATE SOURCES ON RICE YIELD AND ON PHOSPHORUS AVAILABILITY EVALUATED BY SEVERAL METHODS
Abstract
A greenhouse experiment was carried out in order to evaluate the residual effect of triple superphos- phate, magnesium thermophosphate (Yoorin), North Carolina rock phosphate and Arad rock phosphate on the rice yield, to determine the efficiency of five soil P extractants, and to test the "Y" leaf as a diagnostic leaf in the phosphated nutrition of rice. On the previous study, four P rates (0, 50 100 and 200 mg/dm 3) were applied to alfalfa grown in a Oxysol (dystrophic Red Yellow Latosol). The residual effect of P was observed by an increase in grain yield and P accumulation in the plant. Resin, Mehlich-1 and Mehlich-3 soil P extraction methods were similar indicators of available P. Soil P extracted by isotopic dilution and by the Bray extractant presenled lower correlation coefficients with the P accumulated in the plant tops. The "Y" leaf was a good indicator of the P nutrition of rice.
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