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Roughstalk Bluegrass Suppression in Alfalfa-Grass Seedings 2002

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Project Leader: Russell R. Hahn, Department of Crop & Soil Sciences

Cooperators: None

Type of Grant: Cultural methods; sanitation; physical controls

Project locations: Findings might be applied throughout the Northeast

Abstract:

A field experiment was established April 30, 2001 at Caldwell Field, Tompkins County, NY to evaluate the value of using recommended and double seeding rates of timothy or orchardgrass for suppression of roughstalk bluegrass (Poa trivialis L.) in alfalfa/timothy and alfalfa/orchardgrass seedings. No data on the effectiveness of the treatments was collected in 2001 since the bluegrass was not present during the establishment year. Bluegrass did invade the plot area in the fall of the 2001 growing season. The plots were harvested four times during the 2002 growing season with cuttings on May 29, July 11, August 28, and October 24. Total forage yields and the percent of the botanical components (alfalfa, timothy or orchardgrass, bluegrass, and forbs) were determined for each harvest date. Roughstalk bluegrass was responsible for 46, 12, 3, and 5% of the total forage yield for the first, second, third, and fourth cuttings respectively. Since the bluegrass was mainly a problem in the first cutting, forage quality analysis was conducted on the botanical components for that cutting only. First cutting forage yield from the alfalfa check was 2.51 tons dry matter/acre (T DM/A) with 40, 4, 46, and 10% of that yield from alfalfa, timothy, bluegrass, and forbs respectively. The use of Select herbicide provided 100% bluegrass control but reduced forage yield to 1.39 T DM/A. Forage yields for the alfalfa/timothy and alfalfa/orchardgrass treatments ranged from 2.36 to 2.97 T DM/A and were similar to the alfalfa check. Each of these alfalfa/grass mixtures effectively suppressed the bluegrass with less than 4% bluegrass in each of the four alfalfa/grass mixtures. Forage from the alfalfa check, which had only 40% alfalfa, had a crude protein (CP) value of 16.6% due to the bluegrass in this treatment, while the alfalfa/Select herbicide treatment, which was 77% alfalfa, had 22.1% CP. The alfalfa/timothy treatments averaged 14.8% CP and the alfalfa/orchardgrass treatments averaged 12.8% CP. Milk yield in 16/T DM and in lb/A were calculated using the yield and forage quality data. Although the milk yield/T DM was highest for the alfalfa/Select herbicide treatment, this treatment would produce less milk/acre than either of the alfalfa/timothy mixtures which were favored by higher yields and with moderate CP values (14.8%). The alfalfa check and the alfalfa/orchardgrass treatments would be expected to produce milk yields/acre between the low for the alfalfa Select herbicide treatment and the high yield for the alfalfa/timothy treatments but not statistically different from either. The reduced milk yield from the alfalfa/orchardgrass treatments can be attributed to lower CP values than with the alfalfa/timothy treatments. The results demonstrate the value of perennial forage grasses, either timothy or orchardgrass, for suppression of roughstalk bluegrass compared with chemical control of this weedy grass.

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