Q & A WITH DR . GRADY MILLER

We are expecting a high amount of use on our bermudagrass fields this spring . Do you have any fertilizer source and rate advice considering our fields will be dormant probably the first two months during this period ?

Increased winter and spring play on fields is a concern for many sports field managers this year . Nitrogen ( N ) fertility programs should be part of the management plan to promote growth , which may help prevent damage from excessive wear . Grasses that are actively growing are generating a wearable surface . So anything that keeps the turfgrass growing should provide a more wear-tolerant field .

While N can promote growth anytime of the year , the larger limitation to growth during the winter is likely to be cool temperatures . And although you did not mention protective covers in your comments , their use is something that you may want to consider . The downsides to covers are the initial investment cost , the labor needed to put them on and remove them , and the required storage space when not in use .

To get back to your question , research suggests that to maintain turfgrass density during periods of its most active growth , bermudagrass could easily take advantage of one-quarter to a half pound of N per 1,000 square feet every seven to 14 days . In your current situation , there is no reason to apply N to dormant bermudagrass , but it is good you are looking ahead to spring . Nutrient uptake has a positive relationship with temperature and sunlight , driving forces in photosynthesis . With cooler temperatures and short day lengths , there is a lower capacity to take up nutrients . So rates should be well below what would be used in summer .

My suggestion for early spring is to use light applications of N that balance applications with field use and turfgrass growth . I would resist putting out a single application that is more than half a pound of N per 1,000 square feet ( about 22 pounds N per acre ) until after the predicted last frost date for your area .

Getting a functional quantity of N to the rootzone can be achieved in many ways . A soluble granular fertilizer can be applied at light rates on a weekly basis to match the

uptake . Slow-release products are great for use during the warm parts of the year , but are less effective when the soil temperature is cool since most rely on microbial activity for nutrient release . So I would save those products for use later in the spring .

I suggest that turfgrass managers begin spring using low rates ( quarter to half pound per 1,000 square feet ) of soluble inorganic fertilizers ( example : Urea , Ammonium sulfate , and Potassium nitrate ) so the N is readily available . The application frequency would depend on the potential growth response with rates and frequency increased with warming temperatures . Slow-release products and higher rates can be incorporated more as temperatures climb . Aggressive bermudagrass growth does not usually start until nighttime temperatures are in the 60s for a week or more .

From a nutritional standpoint , that is about the best you can do . If the field is damaged during spring , use the long , warm days of summer to push bermudagrass recovery . And do not forget to get a soil test to make sure other nutrients are in adequate supply .

I would like to dispel one N fertility myth before ending this discussion . A lot of older turfgrass literature stated that late-season soluble N increased bermudagrass winterkill . But research conducted over multiple years in Alabama , Arkansas , Mississippi , Texas and Virginia all found that late-season soluble N promoted better fall color and better spring greenup of hybrid bermudagrass . None experienced an increase in winter damage . So do not be afraid to fertilize your bermudagrass in the fall . Moderate fall rates may play big dividends in fall color and spring turfgrass health . SFM

Grady Miller , Ph . D . Professor and Extension Turf Specialist North Carolina State University

Questions ? Send them to Grady Miller at North Carolina State University , Box 7620 , Raleigh , NC 27695- 7620 , or e-mail grady _ miller @ ncsu . edu Or , send your question to Pamela Sherratt at 202 Kottman Hall , 2001 Coffey Road , Columbus , OH 43210 or sherratt . 1 @ osu . edu

50 SportsField Management | March 2021 sportsfieldmanagementonline . com