FERTILIZER RATES AND YIELD AND QUALITY OF GRASS HAYS IN SOUTHERN PUERTO-RICO

The mean dry matter yield (DMY), in vitro organic matter digestibility (IVOMD), crude protein (CP) content, and mineral concentrations of ha ys from four tropical grasses, each receiving four fertilizer levels, were studied at the Agricultural Experiment Station at Juana Diaz in t he semiarid southern region of Puerto Rico. Significant (P = 0.05) dif ferences in the mean DMY were observed among the grasses receiving the four fertilizer levels during all periods studied. Total DMY of the C ynodon dactylon cultivar, PRPI 11504, was superior to that of the Digi taria eriantha and two Digitaria decumbens cultivars under evaluation. Fertilizer level had little effect on the levels of trace elements, p hosphorus and magnesium content of hays, but hay CP, calcium, sodium a nd potassium content were significantly (P = 0.05) affected by the lev el of fertilization. An increase in the rate of fertilizer was always followed by a decrease in the iron content.