Dry matter yields and nutritional composition of corn and sorghum for silage in Florida

The objective of this retrospective study was to determine the effect of forage type and planting season on DM yield and nutritional composition of corn and sorghum for silage. Data were obtained from hybrid test trials performed by University of Florida. Evaluated forages included corn, forage sorghum (FS), and sorghum Sudan (SS) planted during spring and summer of each year from 2008 to 2014. Plantings occurred on March 17 (±13 d) and July 17 (±3 d) for corn and April 16 (±9 d) and July 18 (±2 d) for sorghum species during spring and summer seasons, respectively. Nutritional composition of harvested and nonensiled samples was determined using NIRS (Dairyland Labs, WI). Data were analyzed using Proc MIXED of SAS. The statistical model included the effects of year (random; df = 6), the treatments (fixed; df = 5), and the residual error (df = 30). Orthogonal contrasts were used to test the effect of planting season (contrast 1), corn vs. sorghum (contrast 2), interaction of season and corn vs. sorghum (contrast 3), FS vs. SS (contrast 4), and the interaction of season (FS vs. SS; contrast 5). Dry matter yield was greater (P < ?? ) for corn than for sorghum. Summer planting resulted in 30 to 35% lower (P < ??) DM yields than spring planting in all forages. Dry matter yields did not differ (P > ??) between sorghum species. Corn had lower (P < ??) concentrations of NDF, greater (P < ??) concentrations of starch, and greater (P < ??) NDF digestibility than sorghum species. Sorghum Sudan had greater (P < ??) concentrations of NDF than FS. In conclusion, spring season forages yielded more DM of better nutritional quality than summer season forages. Also corn yields more DM of better nutritional quality than sorghum forages.