Characterizing Goosegrass and Crabgrass in Pasture Based Dairy Systems.

The number of cows housed on pasture-based dairies has increased recently in Georgia. Pasture-based dairies utilize bermudagrass for summer grazing, which is overseeded with winter annuals for cool season grazing. Goosegrass and crabgrass are summer annual weeds that compete with bermudagrass and can cause stand decline. There is circumstantial evidence that winter annual forages suppress summer annual weeds. Thus, the objectives of this research are to determine whether winter annuals inhibit goosegrass and crabgrass germination and growth, and determine botanical composition of bermudagrass and goosegrass under different population densities. A small plot experiment was designed to investigate the effect of overseeding bermudagrass with winter annual forages and supplementary irrigation on species composition during spring and summer. Point-frame quadrat estimations of goosegrass, crabgrass, and bermudagrass indicated that annual ryegrass temporarily suppressed both weeds under irrigated conditions. Drought prevented seedling weed development under dry land conditions. A second experiment was designed to simulate competition between goosegrass and bermudagrass. Goosegrass seedling plants were established at 0, 2.7, 8.1 and 13.5 plants/m2 within Tifton-85 bermudagrass, irrigated, and harvested every 14 d. Increasing population density of goosegrass increased the probability of goosegrass presence, but frequent defoliation provided the bermudagrass with a competitive advantage. Observations on a commercial farm demonstrated that grazers preferred bermudagrass over goosegrass, thus providing goosegrass a competitive advantage. A greenhouse experiment was also conducted to determine the forage quality and anti-quality parameters goosegrass compared with crabgrass and bermudagrass.