Subsequent applications of nitrogen during the first fall can help to speed establishment. Applying urea – i.e., 46-0-0 – at a total rate of 1 to 1.5 pounds per 1,000 square feet spread out over several weeks is worthwhile in situations where getting to a complete green sward as soon as possible is of the utmost importance. With that said, you do not have to fertilize after the initial starter application until the following year, when turf growth resumes in spring. For annual maintenance, nitrogen should be applied in the range of 2 to 3 pounds per 1,000 square feet. Using primarily slow-release nitrogen sources can help to avoid flushes of growth. The turf should be fed consistently from spring through fall so one species is not favored. Applying fertilizers in spring and fall only could hurt the bermudagrass whereas a summer-only schedule would put the Kentucky bluegrass at a disadvantage.
Height of cut will also impact the amount of fertility that is required to maintain healthy turf. Lower heights will necessitate more fertility inputs. The lowest recommended height of cut is 0.5 inch, though many superintendents with bluemuda seem to prefer a slightly higher cut of 0.75 to 0.875 inch. This range seems to provide the most favorable lie in bluemuda fairways and the turf is better able to withstand environmental stresses.
Watering practices will need to be adjusted when going from a pure stand of bermudagrass to bluemuda. The Kentucky bluegrass will likely require some added irrigation during the heat of the summer, so be on the lookout for wilting. However, the total amount of additional water should not be overwhelming as the new cultivars are quite drought tolerant.
Regular cultural practices like aeration and verticutting should occur when both grasses are growing. Late spring is the best timeframe to complete such tasks. Don’t be too aggressive if the forecast calls for high temperatures as you do not want to cause significant injury to the bluegrass. Waiting until fall to complete such work is less than optimal as this timing could limit bermudagrass recovery prior to winter dormancy. Therefore, a mid-to-late May window is advised.
Plant growth regulators like trinexapac-ethyl can be safely applied to bluemuda. A rate of 9 fluid ounces per acre on four-week intervals is appropriate. Yet, under most scenarios plant growth regulators are not needed as bluemuda offers good quality without them. These products will probably only be useful when trying to keep the turf at the lowest height of 0.5 inch.
Although having to manage both cool- and warm-season turf within the same stand might seem like a challenge for herbicide selection, it is not of great concern as weed development is typically minimal with bluemuda. Some amount of Poa annua can be expected during the initial establishment period but it should wither away during the summer heat and not be a repeat issue. Once the bluemuda has matured, its density seems to do a good job at preventing future weed infestations. If you do find it necessary to utilize herbicides, a formulation of prodiamine for preemergence and Trimec Southern – i.e., dicamba + MCPP + 2,4-D – for postemergence broadleaf weed control are good options. Just be cognizant of the different rate thresholds for both bermudagrass and Kentucky bluegrass as they will vary on the label. Go with a rate that is within the acceptable range for both species to prevent unintended turf injury.