Mefluidide effect on Caucasian bluestem leaves, stems, forage yield, and quality

Abstract

'Caucasian’ bluestem [Rothriochloa caucasis (Trin.) C.E. Hubb.] provides high quality forage during early summer but growth of floral stems causes a rapid decline in forage quality. In 1985 and 1986 mefluidide [N-(2,4-dimethyl-S-{[(trifluromethyl)sulfonyl] amino)-phenyl)acetamide, a growth regulator, was applied to Caucasian in late May, early June, aud mid June at 0.00, 0.28, 0.56, and 0.84 kg/ha to determine which combination of date and rate of application would effectively decrease number of floral stems and yet increase forage quality. Caucasian was grown on a Pratt fine sandy loam (Thermic Pasammentic Haplustalfs) soil 6 km north of Fort Supply, Okla. Plots (1.5 by 5 m) were replicated 4 times in a randomized complete block design with a factorial treatment arrangement. Forage was harvested above a 6-cm stubble height in late July. On the control plots, the in vitro dry matter digestibility (IVDMD) and crude protein of leaves was 6.5 and 2.0 percentage units higher than stems. Leaves accounted for 40% of the forage yield the first year and 64% the second year. Mefluidide was most effective if applied late May. Response surface analysis showed that mefluidide (0.56 kg/ha) application in late May decreased number of floral stems 35 to 509, forage yields 20 to 251, and leaf yields 7 to 25%. In 1985, mefluidide had no effect on IVDMD and crude protein of leaves, stems, and whole plants. In 1986, application of 0.56 kg/ha mefluidide in late May increased leaf, stem, and whole plant IVDMD by 1.2, 2.7, and 2.0 percentage units and crude protein by 0.5 to 1 percentage units. Mefluidide did not decrease number of floral stems enough nor increase leaf yield and forage quality enough to be economically used on Caucasian to improve livestock gain during late July.