RATOON CROPPING FORAGE SORGHUM FOR SILAGE - YIELD, FERMENTATION, AND NUTRITION

Two field experiments were conducted on Lexington silt loam soil (fine -silty, mixed, thermic Typic Paleudalf) to identify a harvest regime t hat would improve the nutritive value of ensiled whole-plant sorghum [ Sorghum bicolor (L.) Moench] while maintaining silage yield. In a 1-yr preliminary study, first-cut sorghum was harvested at mid-vegetative, late-vegetative, boot, bloom, and hard-dough stages of maturity. Regr owth was harvested in late August. In a 2-yr experiment, yield, ensili ng losses, intake, and in vivo apparent digestibility of vegetative so rghum (initial and ratoon cuts wilted 24 h) were compared with direct cut hard-dough-stage sorghum. Forages were stored in 1.8-Mg-capacity ( fresh wt.) experimental sites and, upon opening, were fed to lambs (Ov is aries). Results from the preliminary experiment indicated that dry matter (DM) yield of first-cut sorghum was greatest at the hard-dough stage; however, nutritional value was greatest for the mid-vegetative stage. Maximum yield for the combined harvests was obtained when first harvest was made at boot stage, The 2-yr experiment average DM yields were 7.3 Mg ha(-1) for combined initial (mid-vegetative stage) and ra toon crops, compared with 6.7 Mg ha(-1) for the single hard-dough-stag e harvest. Ensiling losses did not differ with harvest regime. Vegetat ive sorghum was more digestible than sorghum harvested at the hard-dou gh stage (670 vs, 570 g kg(-1)). These studies suggest that sorghum ha rvested twice per season (with wilting) will produce a higher quality silage than a single hard-dough stage cutting, without yield reduction .