Salinity concerns in putting greens are common in the Southwest and Poa annua greens irrigated with saline water are especially susceptible to damage. Bermudagrass greens are at far less risk, but when those greens are overseeded with Poa trivialis the overseed grass is at great risk of decline from salinity stress and rapid blight disease.
While fungicides are an important part of the disease management program, an effective leaching program to push salts down past the rootzone is critical. Leaching is the process of percolating water through the soil profile to move salts below the rootzone. However, leaching with full-circle sprinklers creates wet green surrounds and approaches and floods bunkers with water. Part-circle sprinklers are more effective, but still result in wet areas around the greens where sprinklers change direction or throw beyond the putting surface. With either type of sprinkler, it’s difficult to apply the 3 to 5 inches of water needed for effective leaching in one evening irrigation cycle.
Recognizing these challenges and having endured years of frustration watching the overseed grass die at Seville Golf & Country Club in Gilbert, Arizona, superintendent Brian Hammond, CGCS, developed a more strategic leaching program. The ‘TifEagle’ greens are overseeded with Poa trivialis, a species that is highly susceptible to salt stress and rapid blight. Beginning in 2022, Brian and his team implemented a different approach to managing the disease, highlighted by a significant shift in their leaching method. The steps Brian and his team employ are listed below:
The team utilizes micro sprinklers that emit water at a very low volume. Each green is set up with three hose lines containing approximately eight micro sprinklers each for a total of about 24 micro sprinklers per green. The sprinklers are set up following play and run from about 7 p.m. to 5 a.m. the following morning. The sprinklers supply about 0.5 inches of water per hour over a 10-hour period, therefore applying the 5 inches needed for effective leaching. The team runs this program on six greens per night when they need to flush.
The frequency of flushing is determined by measuring soil salinity using a hand-held salinity meter. Once a threshold is reached, the greens are leached. The team uses a threshold of 1.5 to 2.0 decisiemens per meter (dS/m), which occurs approximately every 2-3 weeks during the overseed season. Post-leaching soil salinity measurements reveal that total salt levels were reduced by 50% to around 0.5 to 1.5 dS/m. This is a significantly greater reduction than with the large overhead sprinklers and yet bunkers and surrounds are only minimally impacted.
In conjunction with this flushing method, irrigation water is treated with a product called N-pHuric (urea-sulfuric acid).
Greens are aerated with small-diameter solid tines routinely to encourage infiltration.
Greens are treated with calcium sulfate prior to leaching events.
Creeping bentgrass was added to the overseed mixture to strengthen the stand. Creeping bentgrass is significantly more salt tolerant than Poa trivialis and not as susceptible to rapid blight disease.
The micro sprinkler leaching program proved very effective and used less water than overhead irrigation. Additionally, the green surrounds and bunkers were ready for play the following morning. For courses with saline irrigation water, this technique could make a big difference in your program to reduce soil salinity in putting greens and other strategic areas. Thank you to Brian Hammond for sharing his efforts at Seville Golf & Country Club and for contributing to this update.
West Region Agronomists:
Brian Whitlark, regional director – bwhitlark@usga.org
Cory Isom, agronomist – cisom@usga.org