Defoliation Management of Tifton 85 Bermudagrass Used as Greenchop in North Florida Dairies.

Tifton-85 bermudagrass adoption by dairymen is increasing because of its potential to remove excess soil nutrient and reduce feed costs when used as greechop.  Defoliation management is critical for yield production as well as persistence of this grass but it has not been evaluated for greenchop production.  To determine the effects of harvest interval and stubble height on herbage yield of Tifton 85 bermudagrass, a randomized complete-block design with a split-plot arrangement of treatments was established in a commercial hay field in north central Florida. Stubble height (8 and 16 cm) was assigned to main plots, and harvest frequency (21, 24, 27 and 35 days) to sub-plots. Across harvest interval, total herbage yields were greater for 8-cm compared to 16-cm stubble (5820 vs. 4430 kg ha^-1, respectively). Comparing defoliation frequencies, total herbage yields were greater when harvested at 27 days (7410 kg ha^-1), followed by harvests at 21 and 24 days (6390 and 6190 kg ha^-1, respectively), and they were lowest at 35 days (5630 kg ha^-1). Under Florida conditions, short stubble heights maximize forage yields, however, taller stubble should be considered to guarantee stand persistence.