Effect of Two Cutting Heights, Four Harvest Intervals and Five Nitrogen Rates on Yield and Composition of Congo Grass under Humid Tropical Conditions

Abstract

The effect of cutting to heights of 2 and 6 inches from the ground, of harvesting every 30, 45, 60, and 90 days, and of applying 0, 200, 400, 600, and 800 pounds of nitrogen per acre yearly on yields and composition of Congo grass, were determined under humid tropical conditions over a 2-year period. Congo grass produced higher yields when cut to a height of 2 inches than when cut to 6 inches, at all harvest intervals and nitrogen rates. The following discussion is therefore limited to results obtained with low cutting. Yields of Congo grass increased, but crude; protein content of the forage decreased with increasing length of harvest interval. Harvest interval did not markedly affect protein yields. Phosphorus and potassium content of the forage decreased with increasing length of harvest interval but the calcium and magnesium content were not affected. Lignin content of the forage increased with increasing length of harvest interval. Yields of Congo grass increased with nitrogen application up to 600 pounds per acre yearly at all harvest intervals and during seasons of both fast and slow growth. Protein content of the forage and protein yields increased with nitrogen rates up to 800 pounds per acre yearly. Recovery of fertilizer nitrogen in the forage averaged about 60 percent at the 600-pound nitrogen rate. Dry matter and phosphorus content of the forage decreased with increased nitrogen fertilization. Nitrogen fertilization did not affect the calcium, magnesium, or potassium content of the forage. Much lower yields were produced during the shorter days and cooler, drier winter months. With close cutting every 45 to 60 days and 600 pounds of nitrogen applied per acre yearly, Congo grass produced about 30,000 pounds of dry forage (65 tons of green forage) containing 9.5 percent protein, or enough cut forage to feed over five 600-pound steers per acre. With high cutting every 30 days, which may approximate yields under grazing management, Congo grass fertilized with 400 pounds of nitrogen per acre yearly produced about 16,000 pounds of dry forage per acre yearly containing 9.7 percent of protein.