Construction projects have been booming in the Southeast and grass is starting to hit the ground. Putting greens are often established with one pound of nitrogen per thousand square feet per week (1 lb. N/1,000/week). Although this rate will provide a rapid grow-in, some fertilizer probably won’t get used by the plants, and surface quality will probably not be optimal when the putting greens are opened for play. When I conducted putting green grow-in experiments at the University of Florida with ‘TifDwarf’ and ‘TifEagle’ bermudagrass, ‘SeaDwarf’ seashore paspalum, and ‘PristineFlora’ zoysiagrass, I observed some interesting results in speed of establishment and surface quality depending on the rate of nitrogen applications.
For the first few weeks, there is typically very little difference between 0.25, 0.50, 0.75 and 1.0 lb. N/1,000/week, regardless of the grass. This could mean a couple of things. Either a preplant complete fertilizer was sufficient over this time frame and/or the 0.25 lb. rate of nitrogen was providing adequate nutrition when sprigs are still trying to take hold. Regardless, it is clear that nitrogen rates should at least be lower than 1.0 lb. N/1,000/week during the first few weeks to avoid waste and possible runoff.
Although the ‘PristineFlora’ zoysiagrass was slower to establish in cooler weather, most plots were only about 10% behind the other grasses when they started reaching 100% cover in an experiment initiated in July in South Florida. All of the different nitrogen rates performed rather similarly for this grass and the 0.25 lb. rate was only about 5% behind the other rates in turfgrass cover.
Seashore paspalum was among the fastest of the grasses studied to reach full cover, regardless of the season, and it did so with as little as 0.25 lb. N/1,000/week. This made it clear that the rate of nitrogen could certainly be reduced below 1.0 lb. N/1,000/week for paspalum and that even lighter weekly rates of nitrogen in the range of 0.1-0.25 lb. N/1,000/week would likely provide similar grow-in speeds.
The bermudagrasses, ‘TifDwarf’ and ‘TifEagle’, grew in rather quickly and similarly with 0.5-1.0 lbs. N/1,000/week. Although about one week slower to reach full coverage, the 0.25 lb. rate of nitrogen provided higher-quality putting surfaces that were firmer and had less mower scalping once established.
In warm weather the bermudagrass, seashore paspalum and zoysiagrass all generally obtained full coverage around the same time with as little as 0.25 lb. N/1,000/week and the lighter fertility rates often provided higher surface-quality ratings. If you are growing in new putting greens this summer, consider applying as little as 0.25 lb. N/1,000/week since grow-in time will be similar to higher nitrogen rates and surface quality will be optimized for opening day.
Southeast Region Agronomists:
Chris Hartwiger, director, Agronomy – chartwiger@usga.org
Jordan Booth, Ph.D., director, USGA Course Consulting Service – jbooth@usga.org
John Rowland, Ph.D., agronomist – jrowland@usga.org