The calcium and phosphorus content of pasture herbage and of various pasture species as affected by fertilization and liming

Calcium and phosphorus, and in some cases total nitrogen and "excess base", were determined on samples of pasture herbage and of pure species of Kentucky bluegrass, white clover, poverty grass, and broomsedge collected during the period of 1931 to 1936. The samples were obtained from variously fertilized and limed plats on two different soils. The herbage from the unproductive soil at Morgantown was only 60% as high in phosphorus as the herbage from the untreated plats of the fertile soil at Moorefield. Liberal fertilization increased the phosphorus content of the herbage to about the same level on the two areas. The percentage increases, however, were 29 at Moorefield and 101 at Morgantown. The calcium content of a mixed herbage is apparently determined largely by the botanical composition of the pasture, which in turn is related to the lime and fertilizer treatments. White clover and some of the common weeds are much higher in percentage of calcium than are the grasses. When grown in association on a number of untreated and of variously treated plats, white clover was found to average 88% as high in phosphorus as bluegrass, but 248% higher in calcium. Phosphorus fertilization increased the phosphorus content of white clover an average of 10% as compared with an average of 40% for Kentucky bluegrass. Broomsedge contained 68 to 86% as much phosphorus and 54 to 76% as much calcium as Kentucky bluegrass. The percentage increase in phosphorus from the use of phosphate fertilizers was approximately the same for broomsedge as for bluegrass. The use of lime on the acid Morgantown plats increased the percentage of calcium in broomsedge by an average of 19 as compared to an average of 36 for bluegrass. Poverty grass averaged less than 70% as high in phosphorus as bluegrass on the untreated plats, but approximately 85% on plats receiving a high amount of phosphorus fertilizer. The percentage increase in the phosphorus content of poverty grass from phosphate fertilizers was approximately twice as high as that for bluegrass. Poverty grass was 49 tO 70% as high in calcium as bluegrass and the average increase in the calcium content of poverty grass from liming was 25% as compared to 36% for bluegrass. The "excess base" content of white clover was 195% higher than of Kentucky bluegrass, whereas broomsedge and poverty grass averaged only 67 and 62% as high as bluegrass, respectively. Broomsedge and poverty grass averaged 76 and 74% as high in nitrogen, respectively, as did bluegrass. It is concluded from a consideration of the data obtained with both the mixed herbage and the individual species that the herbage from many West Virginia pastures is likely to be insufficient to meet the phosphorus requirements of the grazing animal, but probably contains, in general, a sufficient amount of calcium. The minimum and average percentages of calcium and phosphorus for Kentucky bluegrass and white clover obtained in this study are compared with the values obtained by other investigators, and the phosphorus content of bluegrass discussed in relation to Macy's theory. The data indicate that the minimum percentage of phosphorus for bluegrass in the vegetative stage of growth is approximately 0.16% and the critical percentage approximately 0.30%.