Effect of Liming and Fertilization on Productivity and Species Balance of a Tropical Kudzu-Molassesgrass Pasture Under Grazing Management

Abstract

The effects of lime, phosphorus, potassium, and nitrogen applications on the productivity, species balance, and chemical composition of a tropical kudzu-molassesgrass mixture growing under grazing management on a latosol in the Humid Mountain Region of Puerto Rico were determined. Yields of tropical kudzu and molassesgrass, and the proportion of kudzu in the mixture were increased by combined applications of lime, phosphorus, and potassium. Yields and species balance were not affected by applications of phosphorus or potassium individually when no nitrogen was applied. However, when nitrogen was applied, the pastures responded in yield to applications of potassium but species balance was not affected. Liming increased both yields of kudzu and the proportion of this legume in the mixture about fivefold. Liming also increased the protein and calcium contents of tropical kudzu and sharply reduced the abnormally high manganese content of unlimed kudzu. The application of 200 pounds of nitrogen per acre yearly increased forage yields, but resulted in the virtual disappearance of tropical kudzu from the mixture. Heavier applications of nitrogen did not further increase yields, but resulted in a marked invasion of the pastures by Para grass. It is apparent that yields of tropical kudzu-molassesgrass pastures cannot be increased much by nitrogen fertilization without erradicating the kudzu. However, if kudzu becomes dominant, as is often the case, it may be possible to restore a desirable species balance by judicious applications of nitrogen.