Forage Yield, Nonstructural Carbohydrate Levels, and Quality Trends of Caucasian Bluestem

Information is limited on growth pattern and the effects of management on regrowth yield, quality, and total nonstructural carbohydrate (TNG) levels of Caucasian bluestem [Bothriochloa caucaslca (Trin.) C.E. Hubb.] grown in the southern Corn Belt. Field studies on a Creldon silt loam soil (fine, mixed, mesic Mollic Fraguidalf) were conducted to determine trends of the above parameters under various primary growth harvests (one-time harvests at 0, 14, 28, 42, and 56 d after 4 June) and summer and late-season regrowth harvests (initial harvest on 18 June and 16 July, respectively, with regrowth harvests 14, 28, 42, 56, 70, and 84 d later). Yield increased linearly (104 and 55 kg ha−¹ d−¹, respectively) for primary growth and summer regrowth, while late-season regrowth yield had a cubic trend (y = 201 − 11x + 2.3x² − 0.02x³; x = days after initial harvest). In vitro dry matter digestibility declined linearly with time (2.9 g kg−¹ d−¹) in primary growth, but the rate of decline varied depending on length of delay for summer and late-season regrowth (y = 548 − 4.0x + 0.26x²; y = 436 + 0.9x − 0.19x², respectively). Crude protein declined quadratically under all treatments (y = 125 − 1.0x − 0.005x²; y = 137 − 3x + 0.001x²;y = 71.2 + 1x − 0.001x², respectively, for primary growth and summer and late-season regrowth). Neutral detergent fiber levels increased linearly for primary growth and late-season regrowth (y = 668 + 1.9x;y = 662 + l.lx, respectively), while summer regrowth response was quadratic (y = 637 + 2.7x − 0.002x²). Digestible dry matter yield increased throughout the season until it declined in late September. Total nonstructural carbohydrate levels were lower than previously found in native C₄ grasses and may not be as important for survival in Caucasian bluestem. Our data indicate that a mid-June defoliation, with further defoliation up to late summer, may optimize Caucasian bluestem's potential in livestock grazing systems. Missouri. Contribution from the Missouri Agric. Exp. Stn. Journal Series no. 10131