5/10/2021 - By Dr. Jeff Atkinson

As summer approaches focus shifts from spring greenup to maintaining high quality turf which can withstand summer stress. Here are 10 tips to keep your turf in top shape through the 2021 growing season.

1. Provide Adequate Fertility

While there is not a single ideal nitrogen rate for every situation, nitrogen feeding through the growing season will enhance turf health. Providing an appropriate rate of nitrogen and other needed nutrients through the growing season will aid in stress tolerance and recovery. Disease epidemics have shown to increase in severity under deficient nitrogen conditions, in both warm and cool season turfgrasses (Dant et al., 2020, Hempfling et al., 2014).

2. Use Seaweed Extract and Fulvic Acid Based Products

Research shows the use of seaweed extract and humic acids will increase turfgrass stress tolerance. Seaweed extract can increase photosynthetic efficiency and capacity under stressful growing conditions. Humic and Fulvic acids are excellent chelating agents and have been shown to promote root growth. Fulvic acid is a type of humic acid but can be distinguished from the larger pool of humic acid by a couple unique characteristics; Fulvic acid is characterized by greater solubility across a wide range of solution pH values, small molecule size, and higher charge density; all which increase fulvic acid effectiveness on a pound for pound basis compared to other humic acids.

Research shows that the application of seaweed extract and humic acid together is better than applying either material separately (Schmidt et al., 2003). Ideally, application of these products should begin in the spring prior to the onset of heat stress. Both products are more effective when applied preventatively, giving them ample time to work without the unnecessary complication of heat stress blocking their progress.

3. Adjust Mower Setup

One of the challenges we face during stressful growing conditions is maintaining both fast green speeds and a healthy turfgrass sward. Unfortunately, the most common approach to gain or maintain putting speed is to lower the mowing height. Not only does lowering the mowing height increase putting speed, it also increases stress to turfgrass plants (Young et al., 2015).

Bentgrass and Poa annua are less active physiologically during summer months as a natural means to survive the stresses of summer. A low mowing height significantly reduces total leaf area of the plant, thus further limiting the ability to conduct photosynthesis. Ideally, mowing heights should be increased during stressful periods so that leaf area can be increased, thus increasing the plant’s photosynthetic capacity, and increasing turf stress tolerance.

While adjusting the mowers to an increased mowing height, go ahead and switch out your rollers to solid instead of the grooved grooming rollers. This too will impart less stress on turfgrass plants.

4. Maintain Potassium Fertility

Potassium has shown to increase stress tolerance of turfgrass when maintained in the tissues at sufficient levels. Further, potassium is frequently deficient in soil tests. As we open the turf canopy and have access to the rootzone during spring core aeration it’s a great opportunity to amend soil macronutrients for the coming season. Consider an application of POLYON® 0-0-50 Micro at 4 lbs. K₂O per 1,000 square feet to open core aerification holes during the last spring aerification. This will provide sufficient potassium, with release for 16 to 20 weeks after application.

5. Help Your Roots Breathe

Many issues related to summer stress are compounded by low soil air-filled porosity and poor atmosphere: soil gas exchange. The frequent use of quad tines or needle tines during stressful summer months will aid in enhancing gas exchange and increasing soil air-filled porosity. Ideally, small solid tines should be utilized on a biweekly basis and the aerification holes left open to promote gas exchange. A simple rolling of the greens with a lightweight roller immediately following needle-tine aerification will close the holes enough to limit effects on putting quality.

This is also a good time to supplement potassium while these small aerification holes are open. Apply POLYON® 0-0-50 Micro as a broadcast surface application, at 1 pound of K₂O per 1,000 square feet (2 pounds of product). Then simply turn the irrigation heads on for a couple of spins and the POLYON® 0-0-50 will disappear into the aerification holes.

6. Utilize Wetting Agents

Many golf course superintendents overwater their greens in an attempt to keep them alive. This approach often creates more challenges as soil air filled porosity is reduced and heat retention is increased. Further, challenges associated with excessive water in the top few inches of the profile may compounded by excessive thatch, topdressing layers, or soil compaction.

The use of Fleet® has proven to be very effective in distributing water evenly through the soil profile. This is important in managing air filled porosity and moderating soil temperatures. Fleet®, when applied and watered-in sufficiently, moves the wetting agent into the profile and enhances consistent water distribution throughout the wetted root zone.

Depending on the specific soil conditions on your property, a different wetting agent may be more appropriate. Consult with your Harrell’s rep to align the correct wetting agent technology with your specific property needs.

7. Apply Title Phyte®

Title Phyte® is not only a great source of potassium, but also to aids in the fight against plant stress.

Phosphites will not replace fungicides and should not be used as such. However, the application and use of phosphites is a no brainer during stressful growing seasons. Title Phyte® should be applied as part of a regular foliar application program throughout the growing season.

8. Apply Preventative Fungicides

Preventative fungicide applications are essential to maintaining healthy turfgrass throughout the summer months. It is important that the appropriate fungicides are utilized and that they are applied at the appropriate timing intervals.

There are several fungicides which have shown to provide plant health benefits in addition to providing disease control. Syngenta’s Action, Bayer’s Stressgard, and BASF’s Intrinsic line of fungicides are a few examples of fungicides with additional plant health benefits. The use of these fungicides is recommended as a key component of your summer fungicide rotation.

9. Air Movement

Air movement is critical to the evaporative cooling process. Without air movement, a high-humidity boundary layer is created immediately surrounding turfgrass leaves. As excessive heat accumulates and transpiration and evaporative cooling slows, photosynthetic efficiency can be dramatically reduced as the photosynthetic system begins to shut down.

Consider how vegetation or other obstructions adjacent to putting greens may negatively impact air movement. In some scenarios it may be beneficial to utilize a moveable fan to encourage air movement or install a permanent fan in areas with chronic air movement limitations.

10. Consult your Harrell's Rep

Your local Harrell’s rep is a wealth of knowledge, utilize them as a resource. Each day our team visits with multiple courses around your area. With these visits our team finds out what other superintendents are seeing out there, how superintendents are finding success against a variety of challenges and serve as a friendly ear during stressful times. If you find your turf up against a new challenge this season, the solution is likely just a Harrell’s rep phone call away.

References:

Dant, LA, SB Martin, LB McCarty, JP Kerns. 2020. Nitrogen source impacts Rhizoctonia leaf and sheath spot severity in ultradwarf bermudagrass. International Turfgrass Society Research Journal. 

Hempfling, JW; BB Clarke, JA Murphy. 2014. Nitrogen Fertility, Mowing Height, and Topdressing Effects on Anthracnose of Annual Bluegrass. Proc of the Twenty-Third Annual Rutgers Turfgrass Symposium. Pp. 37-38.

Schmidt, RE; EH Ervin, X Zhang. 2003. Questions and answers about biostimulants. Golf Course Management. June pp. 87-99.

Young, J, M Richadson, D Karcher. 2015. Creeping bentgrass putting green response to combined mowing, rolling, and foot traffic under environmental stress. Agron. J. 107:6:1959-1966.