Subtropical Grass Species Response to Different Irrigation and Harvest Regimes

Perennial grasses can be grown in subtropical areas of the world having little frost damage, but, in many areas low temperatures (1 to 10 C) at higher elevations and lack of moisture may restrict growth of most subtropical forages and create critical feed shortages for livestock. A study of the seasonal distribution of forage production of subtropical grasses was conducted to determine production and quality and to develop improved management practices. Sixteen grasses (four Cynodons, three Paspalums, eight Digitarias, and one Brachiaria) were grown with and without irrigation and harvested at two stubble heights (5 and 10 cm) at 30-day intervals for 30 consecutive months (March 1973 through August 1975). The experiment was conducted at the Immokalee Research Center in south Florida on a sandy siliceous, hyperthermic, Arenic Haplaquod (Immokalee fine sand) soil. Winter forage production (October through March) was highest for Cynodon spp (27% of total annual yield) and lowest for Paspalum spp. (14% of total annual yield). Plants cut at a 5-an stubble initially outyielded plants harvested at 10 cm. However, after 2.5 years little difference was observed in dry matter yield between stubble heights, except for the Paspalum spp. and Brachiaria sp. which continued to produce more forage at the 5cm stubble height. Little difference was observed in percentage crude protein and IVOMD between grass entries harvested during the summer growth period with the exception of Brachiaria which was significantly higher in IVOMD. Both crude protein and IVOMD were much lower in forage harvested during the summer than the winter for all grasses, again with the exception of the IVOMD for Brachiaria which had a summer-winter range of 58 to 64%. This entry was one of the highest in dry matter yield, crude protein, and IVOMD percentage, but produced 83% of its dry matter during the summer. Irrigation had little effect on dry matter production at any season. Higher IVOMD was obtained from cut short with no irrigation. These data indicated that Cynodons harvested at a 5-cm stubble produced highest dry matter production during the cool winter season, containing high crude protein and IVOMD levels. Dry matter yields in summer were 200 to 300% higher than in winter, however, forage quality was much lower during the summer.