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Effect of Rainfall and Fertilization on the Yield and Chemical Composition of Alfalfa over a 10-Year Period in North Central Oklahoma¹

ABSTRACT

Climatic environment had a greater influence than soil treatment on the quantity of nitrogen, calcium, potassium, magnesium, and phosphorus in 26 cuttings of alfalfa hay grown on the Oklahoma Agricultural Experiment Station, Perkins Farm, from 1937 to 1946. The protein content of the first cutting of alfalfa was equal to, or higher than, the protein content of the second or third cuttings of hay in 8 out of 9 years. The calcium content of the hay was usually high when soil moisture was low, and low when soil moisture was high during the growing period. The minimum and maximum percent of calcium in different cuttings varied nearly 100%. The potassium and phosphorus content of different alfalfa cuttings varied more than 100%. A luxury potassium consumption by alfalfa occurred on this soil. Lower phosphorus percentages usually were observed in the alfalfa hay when rainfall was low for several weeks before the crop was cut. Factors which increased or decreased the quantity of phosphorus obtained by the alfalfa plants from the natural phosphates in the soil had a similar influence on the uptake of applied phosphates. The average absorption of phosphorus from rock phosphate by alfalfa was similar to the quantity of phosphorus obtained from superphosphate on unlimed soil, but was slightly lower on the limed plots. A greater variation occurred in the nitrogen and phosphorus content of the stems than in the leaves of mature alfalfa plants grown on variously treated plots.

¹ Contribution of the Department of Agronomy, Oklahoma Agr. Exp. Sta.

² Assistant Director, Oklahoma Agr. Exp. Sta., formerly Professor of Soils.

Received for publication August 8, 1955. Accepted for publication May 1, 1956.