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Effectiveness and Recovery of Phosphorus and Potassium Fertilizers Topdressed on Meadows¹

ABSTRACT

A two-year experiment was conducted in which phosphorus and potassium fertilizers were topdressed each year on an alfalfa-timothy meadow. In 1950, rates of 0, 60, and 120 pounds per acre of P₂O₅ and K₂O were applied alone and in all combinations. In 1951 each plot was split with a factorial of 0 and 60 pounds per acre of P₂O₅ and K₂O. Determinations of yield, botanical composition and chemical composition of the hay were made. Soil analyses were made to determine depth distribution of available nutrients in the soil.

The soil was very low in "available" phosphorus and potassium and large increases were obtained from the fertilizer applications.

There was competition between the alfalfa and timothy for both phosphorus and potassium. Alfalfa was the dominant competitor for phosphorus while timothy offered the most competition for potassium.

Very efficient recovery of the topdressed phosphorus was indicated.

The apparent recovery of applied potassium was as high as 100% from several treatments. The chemical data indicate that even the maximum application of 180 pounds of K₂O per acre in the two years was not sufficient for maximum yield on this very potassium deficient soil.

Soil tests at the end of the experiment indicate a considerable increase in "available" phosphorus in the surface layer from applications of 120 or more pounds per acre of P₂O₅. The residual effect of potassium applications could not be detected by soil tests.

¹ Journal Paper No. J-2227 of the Iowa Agr. Exp. Station, Ames, Iowa, Project 1189. Presented before Section IV, Soil Science Society of America, Nov. 20, 1952.

² Assistant professor, professor and associate professor of soils, respectively.

Received for publication May 8, 1953.