Defoliation effects on production and morphological development of little bluestem

Abstract

Response of key warm-season grasses to time, frequency, and duration of defoliation is needed to develop grazing systems for the Nebraska Sandhills. A 3-year (1986 to 1988) study was conducted on a Valentine fine sand (mixed, mesic Typic Ustipsamments) at the Gudmundsen Sandhills Laboratory near Whitman, Nebraska, to determine the effect of defoliation on little bluestem [Schisachyrium scoparium (Michx.) Nash]. Treatments were: 1 defoliation (to 7 cm) on 10 June, 10 July, or 10 Aug.; 2 defoliations on 10 June and 10 Aug.; and 3 defoliations on 10 June, 10 July, and 10 Aug. Control plants were harvested only at the end of the growing season (October). All plots receiving summer defoliation were harvested in October to obtain aftermath yield. Treatments were initiated in 1986, 1987, and 1988 and the effects of 1, 2, and 3 years of defoliation on dry matter (DM) yield, bud and tiller numbers, and tiller weight were measured. Experimental design was a split block with 4 plants as replications. In the flrst year of treatment annual DM yield from control plants was 2 times greater than that from all defoliated plants, but bud and tiller numbers were similar. In the second year of treatment, all treatments reduced annual DM yield and morphological development below that of the control if precipitation was subnormal, but not if precipitation was above normal. In the third year of defoliation, with above-normal precipitation, single June or July defoliations produced DM yields and morphological development similar to that of the control, but single August or multiple defollations generally reduced yield and development. Little bluestem may not persist if exposed to multiple, close defoliatlons during the growing season.