Nutritive Value, Fermentation Characteristics and Aerobic Stability Assessment of Soybean (Glycine max L.)-Sorghum (Sorghum bicolor L.) Mixture and Soybean Treated with Molasses.

Soybean (Glycine max (L.) Merrill) produced mainly for grain has potential for use as forage (either hay or silage).  A forage soybean (PR 22-3) produced high quality hay when baled 84-d after planting (R₆ full seed development).  Its potential to supplement protein in diets of ruminants as silage has not been evaluated.  The objectives of this study was to assess crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF) concentrations, fermentation characteristics (pH, % lactic, acetic and butyric acid) and aerobic stability of ensiled soybean-sorghum (Sorghum bicolor L; SS) mixture (50:50) , soybean treated with molasses (SM) and soybean alone (control).  Replicated soybean (R₆) and soybean-sorghum plots were harvested at 84-days after planting. The harvested above-ground plants were chopped at 2-cm length and ensiled in 15-lt micro-silos. Molasses was applied at 6% concentration of fresh soybean plant weight.  Past twenty one days, the micro-silos were opened and representative fresh samples taken, dried and ground for nutritive value. Frozen samples were sent to the lab for fermentation characteristics analysis. Highest dry matter yield resulted (P<0.05) in SS mixtures (4.0 Mg ha^-1).  Soybean-sorghum silage presented lowest dry matter (DM; 32%), CP (16%) and NE_L (1.13 Mcal kg^-1) and higher NDF (56%) than either SM or control. However, SS improved fermentation characteristics resulting in lower pH (4.1), lactic acid (7.8%), and NH₃ (8.2%) than the SM or control. There were differences in aerobic stability between ensiled soybeans with pH values of 4, 4.4 and 4.8 for SS, SM and control, respectively. In conclusion, SS silage mixture had higher DM, better fermentation (lower pH) than either SM or control and would be a good option to produce high quality soybean silage in the tropics.