Growth Characteristics of Guinea Grass on the Semiarid South Coast of Puerto Rico, and the Effect of Nitrogen Fertilization on Forage Yields and Protein Content

The stocking level and hence the productive capacity of pastures in the nonirrigable, semiarid region of Puerto Rico is limited by the pasturage available during the approximately 5-month dry season of December to April. This, in turn, largely depends on the quantity and quality of the roughage carried over in the field from the wet season when an excess of forage is produced. The application of 100 pounds of nitrogen per acre to a closely grazed Guinea grass pasture toward the end of the wet season, November 1, resulted in a marked increase in the dry matter from 3,555 to 5,520 pounds per acre of protein yields from 238 to 486 pounds per acre, and in the protein content from 6.7 to 8.8 percent, of the forage carried over in the field for grazing toward the end of the dry season. Total yields of dry forage produced during the year following application of the fertilizer were increased from 9,710 to 12,645 pounds per acre. Total yields of protein were also increased by this treatment from 608 to 921 pounds per acre. About 50 percent of the nitrogen applied was recovered in the forage. Heavier applications of nitrogen tended to increase protein yields and also the protein content of the forage, but did not affect yields of dry matter. Through good management and proper fertilization with nitrogen it appears possible markedly to increase the carrying capacity of Guinea grass pastures in this area