Availability of Phosphorus in Central Oregon Soils in Comparison with Selected Oregon Soils PDF Download

Author: Jose Fernando Araos
Publisher:
ISBN:
Category : Soils
Languages : en
Pages : 122

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Book Description
The objectives of this study were to evaluate and compare the availability of native and applied P in Central Oregon pumice soils with that in Willamette valley soils and calcareous soils from Eastern Oregon. The experimental work to meet these objectives included laboratory and greenhouse studies. The removal of P from solutions in one hour of eqilibration was much greater in the Willamette valley soils than in the pumice soils, and greater in the pumice soils than in the calcareous soils from Eastern Oregon. The ratio between the P removal by the Willamette valley soils and the removal by the pumice soils increased with the rate of P application, while the ratio between the removal by the pumice soils and that by the calcareous soils was fairly constant at different rates of P application. Generally more P was extracted from these soils by the method of Bray N[superscript o][subscript -]1 than by the methods of Olsen 1:10 (soil to extractant ratio = 10) and Olsen 1:20, and more P by these methods than by that of Morgan. On the Willamette valley soils the method of Olsen 1:20 extracted about 1.5 times the amount of P extracted by the Olsen 1:10 method, on the pumice soils the Olsen 1:20 method extracted slightly more P than the Olsen 1:10 method, while on the calcareous soils the Olsen 1:10 method extracted almost the same amount of P as the method of Olsen 1:20. When Morgan's procedure was compared with the methods of Bray N[superscript o][subscript -]1 and both Olsen's procedures, it extracted proportionally more P on the calcareous soils than on the pumice soils, and more P on the pumice soils than on the Willamette valley soils. With any group of soils and with all the soils considered together the values of available P obtained by the methods of Olsen 1:10, Olsen 1:20, and Bray N[superscript o][subscript -]1 were highly correlated. The correlation between the method of Morgan and the methods of Olsen 1:10, Olsen 1:20, and Bray N[superscript o][subscript -]1 varied with the group of soils considered, being higher on the Willamette valley soils and lower on the calcareous soils. In greenhouse experiments with oats, P applications did not increase yields but did increase the %P and mg. P/pot in the tops of plants. In most of the experiments, particularly those with the pumice and the calcareous soils, the oat plants showed disorder symptoms which increased with P application. It is possible that these symptoms had been related to an interaction between P and one or more essential nutrients. In the greenhouse experiments with subterranean clover, no disorder symptoms were observed, P application increased yield and %P in tops in almost all the experiments, and the mg. P/pot in all the experiments. Simple correlation coefficients between available P values by different methods and the percent P in tops and the mg. P/pot were in most cases high, but varied depending on the method, effect considered, and crop. The correlation values obtained by the method of Morgan were more variable than those obtained by the Olsen 1:10, Olsen 1:20, and Bray N[superscript o][subscript -]1 methods. The recovery of P applied to the soils was measured by short equilibration with P solutions, by the methods of Olsen 1:10, Olsen 1:20, Bray N[superscript o][subscript -]1, and Morgan, and by oats and subterranean clover in the greenhouse. These different procedures were generally in good agreement with respect to the relative recovery of P from the different soils. The recovery was larger in the calcareous soils, followed by the pumice soils, and last by the Willamette valley soils. The difference in recovery between the calcareous and the pumice soils was smaller than the difference between the pumice and the Willamette valley soils. In most cases a slightly larger percent of the added P was recovered at the rate of 50 ppm. P application than at the rate of 25 ppm. P. The recovery by plants in the greenhouse was more variable than the recovery by the laboratory methods in this respect. Among the different procedures used to measure the recovery of P, both by chemical extraction and by plants in the greenhouse, the highest recovery was obtained by the method of Bray N[superscript o][subscript -]1 and the smallest recovery was obtained by the method of Morgan.