The chemical composition of pasture species of the northeast region as influenced by fertilizers

Chemical analyses of over 300 samples of pasturage from 17 variously fertilized permanent, grazed plots were made from 1932 to 1936. The fertilizers ranged from superphosphate alone to complete minerals (PLK) plus 94 pounds of N per acre annually. Superphosphate caused the greatest improvement in important nutritional characteristics, namely, a 25% increase in protein, a 5% decrease in fiber, and a 50% increase in P. In these respects, further advances were due to adding limestone and, or, nitrogenous fertilizers with superphosphate. Superphosphate (16%) at 500 pounds per acre in 1924 was responsible for a 40% increase in the P in the pasturage in 1938. This emphasizes the importance of conducting pasture experiments over long periods. The Ca:P ratios varied from 1.4 for the PLK plus high N plots to 2.9 for the non-phosphated pastures. The Si, Fe, and Al contents of the unfertilized vegetation were each approximately double those found in the P or P+ pasturage. Mn was consistently 60% higher in the grasses from the unlimed plots. S, Cl, and Mg did not vary so much as the elements just mentioned and the effects of fertilization were much less evident. Intra-seasonal variations m composition of samples from the same plot were equivalent to 25% frequently and 40% occasionally, of the annual means. These facts illustrate the difficulty of obtaining fresh pasturage of uniform quality for feeding trials. The N content of timothy, mowed June 1, was not increased by 28 pounds of N but was raised by 56 pounds of N per acre applied annually in April. In this case, early cutting was a much more important factor than nitrogenous fertilizers. On seeded, lawnmowed plots, the N, P, K, Ca, and Mg contents of pure stands of Kentucky bluegrass and Rhode Island bent grass were influenced appreciably by the source of fertilizer nitrogen. Materials carrying Na increased the K in the grasses, while magnesic fertilizers had the opposite effect. On this soil (pH 5.3), the use of physiologically neutral or alkaline N carriers resulted in higher N, P, and Ca contents in the grasses. It is concluded that many carefully conducted feeding trials will be required before the results of chemical analyses of pasturage can be interpreted in terms of nutritional values.