The Behavior of Applied Phosphorus and Potassium in Organic Soil as Indicated by Soil Tests and the Relationship between Soil Tests, Green-Tissue Tests and Crop Yields
1953
Bigger, T. C. | Davis, J. F. | Lawton, Kirk
Phosphorus and potassium were extracted from organic soils by rapid test methods using 0.1 N HCl — 0.03N NH₄F, 0.135 N HCl, and 0.018 N CH₃COOH for phosphorus and 23% NaNOₐ, 0.135 N HCl, and 0.018 N CH₃COOH for potassium. The extractable phosphorus was determined by a colorimetric method and the extractable potassium was determined with a flame photometer, except for the sodium nitrate extracts in which case a cobaltinitrite procedure was employed. A highly significant correlation exists between the amount of phosphorus and potash applied and the amount of phosphorus and potassium extracted from the soil. Applied phosphorus remained in the surface soil while potassium was found in the 12 to 18-inch depth. Periodic green-tissue tests of sugar beets and peppermint revealed a seasonal variation in the composition of water extractable phosphorus and potassium in these plants. Sugar beets contained 1,800 ppm and peppermint 1,000 ppm of potassium when the plants showed foliar symptoms of potassium deficiency. In correlating rapid soil tests, green-tissue tests, and crop yields, it was impossible to establish optimum levels of phosphorus and potassium for maximum yields of sugar beets and peppermint because of the following factors: the physiological nature of the plants, the seasonal variations in plant composition, the differential response of the crops to the fertilizer ratios, and the limitation of the fertilizer analyses and rates of application in this experiment.
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