Roughstalk Bluegrass Suppression in Alfalfa-Grass Seedings
Project Leader: Russell R. Hahn, Department of Crop & Soil Sciences
Type of Grant: Cultural methods; sanitation; physical controls
Project locations: Findings might be applied throughout the Northeast
A field experiment was established April 30, 2001 at Caldwell Field, Tompkins County, NY to determine 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 treatment effectiveness was collected in 2001 since the bluegrass was not present during the establishment year. Bluegrass did invade the plot area in the fall of 2001. The plots were harvested four times in 2002 and three times in 2003. Total forage yields and the percent of the botanical components (alfalfa, timothy or orchardgrass, bluegrass, and other weeds) were determined for each harvest date. In the alfalfa check plots, roughstalk bluegrass was responsible for 46, 12, 3, and 5% of the total forage yield for the first, second, third, and fourth cuttings respectively in 2002 and for 30, 18, and 13% of the total forage yield for the first, second, and third cuttings respectively in 2003. Since bluegrass was mainly a problem in the first cutting, forage quality analysis was conducted on the botanical components for those cuttings only. In 2002, first cutting forage yield from the alfalfa check was 2.51 tons dry matter/acre (T DM/A) with 46% of that yield from bluegrass. In 2003, first cutting forage yield from the alfalfa check was 1.68 T DM/A with 30% of that yield from bluegrass. The use of Select herbicide provided 100% bluegrass control both years but reduced forage yield to 1.39 and 1.11 T DM/A in 2002 and 2003 respectively. 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 in 2002. In 2003, the alfalfa/timothy yields averaged 1.71 T DM/A and were similar to the alfalfa check. The alfalfa/orchardgrass mixtures yielded more than the alfalfa check and averaged 2.08 T DM/A. Each of these alfalfa/grass mixtures effectively suppressed the bluegrass. There was no bluegrass in either of the alfalfa/orchardgrass treatments in either year and bluegrass made up no more than 8% of the first cutting yield for either of the alfalfa/timothy treatments either year. Forage from the alfalfa check, which had 40 and 55% alfalfa in 2002 and 2003 respectively had a crude protein (CP) value of 16.6% in 2002 and 17.4% in 2003 due to the bluegrass in this treatment, while the alfalfa/Select herbicide treatment, had 77% alfalfa and 22.1% CP in 2002 and had 82% alfalfa and 19.3% CP in 2003. The alfalfa/timothy treatments averaged 14.8% CP in 2002 and 16.9% CP in 2003. Alfalfa/orchardgrass treatments averaged 12.8% CP in 2002 and 11.1% CP in 2003. Milk yield in 1b/T DM and in lb/A were calculated using the yield and forage quality data. Although the milk yield/T DM was among the highest for the alfalfa/Select herbicide treatment both years, this treatment would have produced less milk/acre than the alfalfa/timothy mixtures in either year. These alfalfa/timothy treatments were favored by higher yields and moderate CP values. In 2002, the alfalfa check and the alfalfa/orchardgrass treatments would have produced 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. Results from 2003 showed all of the alfalfa/timothy and alfalfa/orchardgrass mixtures, as well as the alfalfa check, would have produced more milk/acre than the alfalfa/Select treatment. 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. They also suggest that the ÒrecommendedÓ seeding rate of 5 lb/A of timothy or orchardgrass in alfalfa/grass seedings is adequate for suppression of the bluegrass and suggest that even lower seeding rates might be adequate. A new experiment using 2.5 and 5 lb/A of timothy or orchardgrass was established in August 2003.