The response of 19 forage grasses to three cutting intervals in the humid mountain region of Puerto Rico was evaluated. Nine Brachiarias, nine Digitarias, and one Cynodon species were evaluated during a 2-year period under cutting management at the Corozal Substation for green forage (GF), dry forage (DF), and crude protein (CP) yields and for dry matter (DM), crude protein (CP), Ca, P, K, and Mg contents. In terms of green forage yield (GFY), the most productive species at the 30-day harvest interval was D. setivalva (PRPI 6402) with 86,794 kg/ ha/year. At the 45- and 60-day harvest intervals, Brachiaria sp. (PRPI 9626) produced 102,116 and 109,213 kg/ha/year, respectively. This species also produced the highest DFY at the 30-day harvest interval with 18,430 kg/ha/year. C. nlemfuensis, var. nlemfuensis (PRPI 2341), stargrass, and B. decumbens (PRPI 5365) produced the highest DFY at the 45- and 60-day intervals with 21,758 and 27,238 kg/ha/year, respectively. The highest CP content at the 30-, 45-, and 60-day intervals was observed on the three Digitaria hybrids, D. pentzii x D. smutzii (PRPI 9621), D. pentzii x D. milanjiana (PRPI 9619), and D. pentzii x D. pentzii (PRPI 9620) with 14.3, 12.0, and 11.1 %, respectively. D. decumbens (PRPI 6439), 'Transvala' Digitgrass, produced the highest CP yield at the 30-day harvest interval with 2, 179 kg/ha/year. Stargrass had the highest CP yield at the 45- and 60-day harvest intervals with 2,141 and 2,030 kg/ha/year, respectively. The P, Ca, Mg, and K contents of the 19 grasses on the average decreased as the harvest interval increased. A sharp decrease (from 1.81 to 1.47 to 1.42%) of the K content of the grasses was observed at the 30-, 45-, and 60-day intervals, respectively. The GFY, DFY, and DM of the 19 grasses increased on the average with the length of the harvest interval. On the other hand, the CP content and yield of the 19 grasses decreased as the harvest interval increased. No significant correlation was obtained between total rainfall, CP, and DFY of the 19 grasses. Significant positive correlations were obtained between DFY of the 19 grasses and average temperature. A significant negative correlation was obtained between average temperature and CP content.

No abstract

Eighteen alfalfa (Medicago sativa) cultivars were evaluated as to dry forage and crude protein yields at the Lajas Research and Development Center; there were 6 cuttings during a 232-day period. Dry forage yields ranged from 4,673 kgfha for Tanverde (lowest) to 11,675 kg/ha for Maracay (highest) cultivar. Good yields were also obtained with Florida 66, Moapa, Peruvian, Certified Mesa Sirsa, and Hayden PX-1 cultivars. Stand persistence declined markedly after the fifth harvest due to Phytophthora root rot infestation. Maracay, Florida 66, and Certified Mesa Sirsa showed the best persistence through the sixth cutting. Mean overall values for neutral-detergent fiber, acid-detergent fiber, lignin, cellulose, silica, crude protein, phosphorus, and potassium contents for the 18 cultivars were 34.86, 29.13, 10.22, 17.08, 1.42, 21.86, 0.36, and 2.08%, respectively. Insects were not a major problem in this study.

Common guinea grass and new accessions of Panicum and Cenchrus grasses were evaluated in a cutting experiment in the semi-arid Lajas Valley over three periods: 126 days of cool weather and short days; 378 days; and nearly 2 years (672 days). The grasses were fertilized with 3,360 kg.ha-1 of a 15-15-10 fertilizer, divided in eight equal applications. The grasses were irrigated. The grasses were harvested every 42 days. In the 126-day period of short cool days, buffel 13084 and guinea 12917 were the highest dry forage yielders, with 11,371 and 11,061 kg.ha-1, respectively. In the 378-day period, guinea #13093, #12917 and #13092 produced statistically similar dry forage yields, which were higher than those of the other grasses. Among the Panicum grasses, guinea 13093 was the highest dry forage yielder (45,574 kg. X-1); among the Cenchrus grasses, buffel 13084 was the highest yielder (35,247 kg. X-1). In the 672-day period, guinea #13093, #13092, and #12917 outyielded var. common and all buffel grasses.

Five Napier grass cultivars (Pennisetum purpureum Schum.) were evaluated under cutting management on a Bayamón sandy loam soil on the northwestern coastal plains of Puerto Rico for a period of 2.05 years without irrigation. Grasses received a high input of fertilizer (4,484 kg/ha/yr) and were harvested every 5') days. Mean dry forage yield for cultivars PRPI 13079, 7350, Merker, 13078, and 532 were 46755, 45449, 39439, 38816, and 37581 kg/ha/yr, respectively. Cultivars 13079 and 7350 had similar dry forage yields, which were significantly (P < .05) higher than those of the remaining cultivars. Cultivar 7350 was the highest crude protein yielder, with 5413 kg/ ha/yr. Mean crude protein, P, K, Ca, and Mg contents for the 5 cultivars were 11.44, .37, 2.56, .31, and .34%, respectively. Leaf/stem ratios for all cultivars ranged from a maximum of 60 to a minimum of 52%. Cultivars 13079 and 7350 are the most outstanding grasses for this region of Puerto Rico. Cultivars 13078 and 532 are recommended as substitutes for the Merker cultivar. However, cultivar 13078 yields can be adversely affected by prolonged droughts.