HARVEST FREQUENCY AND BURNING EFFECTS ON MONOCULTURES OF 3 WARM-SEASON GRASSES

Harvest frequency and burning can affect forage yield of monocultures of switchgrass (Panicum virgatum L.), big bluestem (Andropogon gerardi i Vitman), and indiangrass [Sorghastrum nutans (L.) Nash], Current inf ormation is based largely on results from mixed stands, A field experi ment was established in 1986, and from 1988 to 1991 treatments were ap plied with burning in March, April, or May plus an unburned control, G rowing-season yield was measured by harvesting 1 (June), 2 (June and J uly), or 3 (June, July, and August) times with unharvested control plo ts included, End-of-season standing crop from all plots was determined after plants became dormant, Treatments were applied to the same plot s annually and were arranged in a split-split plot, randomized complet e block design, The main plot was species, subplot was burn date, and sub-subplot was harvest frequency, Burning reduced yields (P<0.01), an d yields were lowest in plots burned in May, Burning reduced yields of indiangrass most (57%) and big bluestem least (15%), In 1989, plots h arvested three times produced yields similar to plots harvested once f or all species, By 1991, yields of plots harvested 3 times per growing -season were reduced (P=0.08) below those of plots harvested once, Yie ld response of species also varied across the study, Growing-season yi elds in 1991 were 113, 67, and 89% of 1989 yields for switchgrass, big bluestem, and indiangrass, respectively, Regardless of burning and ha rvest frequency combination, switchgrass produced as much or more herb age than the other species.