Abstract
Three varieties of sorghum [Dynagrow: 705F (MED), F73FS10, (TALL) and F72FS25BMR (BMR)] were evaluated for their potential as a late season silage crop as part of a corn/sorghum/annual ryegrass crop rotation program. The experiment was conducted in Kinder, LA. After harvesting of corn silage in August, the field was planted (d 0) at 4 kg/ha in early September. Atrazine (1 L/ha) and Parallel (1 L/ha) were applied pre-plant for weed control. Liquid urea ammonium nitrate (32% N, 33.6 kg/ha) was side-dressed on d 30. Two applications of insecticide (Kendo, 18.7 L/ha) were applied on d 14 and 30. Three adjacent 4 ha plots were each planted with a single variety of sorghum. On d 90, 3 samples (2.7 m X 1.5 m) from each plot were evaluated for plant population, yield, stalk diameter, and plant height. Three 3.8 L plastic bags were filled with a homogenized sample of each variety of sorghum and analyzed (Agri-King Nutrition, Inc., Fulton, IL) for plant composition and digestibility. At harvest, the BMR variety was the most mature (hard dough stage) with MED and TALL varieties in milk to soft dough stage. The BMR variety had the lowest yield (P < 0.05). Crude protein content was greatest (P < 0.05) in the MED variety. Plant maturity negatively influenced the CP content of the BMR variety. Although yield was greatest (P < 0.05) in the TALL variety, the resulting plant height increased the susceptibility to lodging. Lodging was exclusive to the TALL variety with approximately 15% (based on visual appraisal) slightly or completely laid down. The MED variety produced nearly equal yield and was the greatest (P < 0.05) in percentages of CP, starch, and fat content. The BMR variety was greatest (P < 0.05) in digestibility and lowest (P < 0.05) in lignin content.