Yield and composition of alfalfa as affected by various fertilizers and soil types

The effect of various combinations of fertilizers upon the yield and upon the mineral and nitrogen content of alfalfa hay grown on various soil types was studied. With few exceptions, the application of fertilizers caused an increased yield on both eastern and western Washington soils, but the average yield on the eastern Washington soils was greater than that on the western Washington soils irrespective of fertilizer treatments. Likewise, the amount of nutrients absorbed per ton of hay was greater on the former soils, but the amount of nutrients removed per acre was very much in proportion to the yield in both areas. Nitrogen, phosphorus, and potassium fertilizers applied alone or in combination to the soils in western Washington had no appreciable effect on the percentage of those elements in the alfalfa hay in the majority of cases, but when applied to eastern Washington soils the phosphorus and potassium contents of the hay had a tendency to increase as a result of phosphate and potash fertilization. The calcium content of the alfalfa did not seem to be affected appreciably by the application of fertilizers, but had a tendency to vary inversely with the yield. On an average the higher percentages of nitrogen and calcium were found in the alfalfa from the eastern Washington soils and the higher percentages of phosphorus in the alfalfa from the western Washington soils. Climatic conditions exclusive of available water appeared to influence the composition of alfalfa in the two areas of the state and on the same experimental plat in successive years. Alfalfa grown in the humid area of western Washington generally contained a higher percentage of phosphorus than that grown in the arid area of eastern Washington. Also, the composition of the alfalfa in successive years on the same soil varied in either area. In the great majority of cases the alfalfa hay contained adequate amounts of the principal mineral elements, phosphorus and calcium, for general feeding purposes of livestock and for the high requirements of lactating dairy cows. In the few exceptional cases in which the phosphorus content of the alfalfa hay was below a certain assumed minimum, it was increased sufficiently by phosphorus fertilization to raise it above that minimum and at the same time result in appreciable increases in yield.