Soluble salts tend to accumulate in putting greens during the summer and cause stress to sensitive turf species such as Poa annua and creeping bentgrass. This is especially true in the Southwest, where many irrigation sources are naturally high in soluble salts, including the recycled water that many courses utilize. Superintendents need to be diligent about monitoring soil salinity and implementing the following preventive programs to avoid turf decline:
Use a portable electroconductivity meter (EC meter) to monitor soluble salt levels in the rootzone. Measurements should be taken to the depth of root growth in the front, middle and back portions of greens on a weekly schedule. The goal is to keep levels below 3.0 decisiemens per meter (dS/m), which is the threshold for damage to sensitive turf species. A reading of 0.7 dS/m on most portable EC meters equates to 2.7 dS/m on a soil laboratory test and is a good threshold for implementing preventive measures.
Schedule deep watering – i.e., leaching – at routine intervals to dilute soluble salts and push them downward beyond the rootzone. Many superintendents will do this at two- to four-week intervals using a cycle and soak irrigation schedule for a total run time of 40 to 60 minutes per green.
Apply soil wetting agents routinely to help improve the effectiveness of leaching practices. These products enhance the effectiveness and uniformity of water infiltration so that less water can be used for leaching soluble salts. Common strategies are to make monthly applications of wetting agents at recommended label rates or use half rates at two-week intervals.
Check soil salinity the day after leaching to make sure soluble salt levels have dropped below threshold levels. Sometimes a second night of deep watering is necessary to do the job.
There is some confusion about practices for managing soluble salts (EC) versus controlling sodium accumulation in the soil. These are two completely different issues. Soluble salts limit water uptake by plant roots. Sodium deflocculates soil and organic matter and can cause direct injury to roots and leaves at high levels. Some believe that adding gypsum (calcium sulfate) before leaching helps control soluble salts. Gypsum is actually a soluble salt and increases the EC of the soil, but it improves water penetration and helps to displace sodium in the soil. Except in extreme situations, gypsum should not be necessary in conjunction with leaching unless soil sodium is greater than 110 ppm. If high levels of soluble salts are the issue, the best strategies are deep watering along with the use of wetting agents.
Golfers may complain about soft or wet conditions for one to two days after deep watering, but it is important for them to understand that these practices are done to prevent turf decline and keep the greens healthy all summer long.
West Region Agronomists:
Patrick J. Gross, regional director – pgross@usga.org
Larry W. Gilhuly, agronomist – lgilhuly@usga.org
Brian S. Whitlark, agronomist – bwhitlark@usga.org
