Effects of Nitrogen Fertilization and Frequency of Cutting on the Yield and Composition of Para Grass in Puerto Rico

Abstract

The effects of rates ranging from 0 to 1,600 pounds of nitrogen per acre yearly and of 40-, 60-, and 90-day harvest intervals on the yield and composition of Para grass were determined over a 1 year period. Yields increased with nitrogen fertilization up to the 800-pound level, while protein content and protein yields increased up to the 1,600-pound level. About half of the fertilizer nitrogen was recovered in the forage when 800 pounds or less were applied per acre. Efficiency of utilization in terms of dry matter produced per pound of nitrogen, decreased rapidly with increasing rates. The phosphorus content of the forage decreased while the lignin content increased with nitrogen rates. Nitrogen fertilization had no pronounced effect on the calcium, potassium, or magnesium contents of the forage. Yields and lignin content of the forage increased while protein, phosphorus, calcium, magnesium, and potassium contents decreased with length of harvest interval. There are marked seasonal variations in yield due primarily to rainfall. With a 60-day harvest interval and 800 pounds of nitrogen per acre yearly, Para grass yielded 30,841 pounds of dry forage, or about 70 tons of green forage, with a 9.5-percent protein content. With this treatment Para grass removed 52.4 pounds of P, 120 of Ca, 524 of K, 77 of Mg, and 469 pounds of N per acre yearly. It is not advisable to use rates of more than 400 pounds of nitrogen per acre per year during dry weather.