WARM-SEASON GRASS PRODUCTIVITY AND GROWTH-RATE AS INFLUENCED BY CANOPY MANAGEMENT

Warm-season grasses adapted to cool-temperate environments can improve the seasonal distribution and supplement the productivity of forage systems in the northeastern USA. Management practices concerning clipping regimes for warm-season grasses grown in the region, are not well understood. A 2-yr field study was conducted to determine productivity and growth rates of flaccidgrass (Pennisetum flaccidum Griseb.), switchgrass (Panicum virgatum L.), bermudagrass (Cynodon dactylon L.), and Caucasian bluestem [Bothriochloa bladhii (Retz.) S.T. Blake] clipped according to sward height criteria. Treatments were replicated three times and included; first clipped at full heading; or 50% removal of short canopy and 50% and 75% removal of tall canopies at vegetative stages. Cumulative yields of warm-season grasses were influenced by a complex clipping treatment, species, and year interaction. When first cut was made at a mature stage, 1990 and 1991 yields were similar, but were greater in 1991 than 1990 when cut early. Cumulative herbage yield of bermudagrass and Caucasian bluestem exceeded that of switchgrass and flaccidgrass when clipping was begun early in the growing season (species x treatment interaction; P less than or equal to 0.01). Mean growth rates were greatest when canopies were managed as hay or when 75% of a tall canopy was removed, and were greater in 1991 than in 1990. Instantaneous growth rates suggest that bermudagrass and Caucasian bluestem appear to be better adapted to repeated defoliation than the tall-growing species. Switchgrass and Baccidgrass may be best used in limited-defoliation or conserved forage situations.