Hydrophobic soils and testing the performance of your wetting agent

Following up on Dr. Fidanza’s excellent post about fairy ring and hydrophobic soils, I thought I’d take a second to show you a picture and video from a wetting agent trial at the University of Wisconsin’s turfgrass research facility and continue the hydrophobic soil discussion. Localized dry spot occurs when organic matter-coated soil particles get too dry. At this point they become water repellent and very difficult to rewet. One way to prevent localized dry spot is to make sure the soil stays wet – but this is challenging because we prefer to keep the turf near the wilt point for optimal playing conditions, agronomics, and environmental stewardship. Therefore, use of wetting agents is the best way to keeping localized dry spot at bay on sandy soils.

Wetting agent trial at the University of Wisconsin’s turfgrass research facility

Yet, when your turf is green you can’t really be sure if it is because the wetting agent is working or if your handwatering crew is just on the ball. But there is a pretty simple way to check the performance of your wetting agent. Take a few soil cores from random spots and let them air dry for a least a week. Then, take an eye dropper and place a drop near the surface of the soil. The drop should will immediately bead up and sit on the soil. For a wetting agent that is doing its job, that bead will completely soak into the soil between 30 seconds and 1 minute. If it sits much longer than a minute, you have some evidence that your wetting agent isn’t performing optimally. The video shows the water drop test for two of the plots from our research study shown in the picture – one with and one without a wetting agent. You can see that it takes about 1 minute for the wetting agent treated drop to soak in to the core, but the core from the plot without a wetting agent didn’t soak in for over 6 minutes.

Check out: Down and Dirty Series presented by DryJect

There are a few potential reason for non-optimal performance from wetting agent treated areas: 1) You may not have watered it in soon enough or long enough after application. I think this is the most common reason for wetting agent failure. These chemicals don’t move through the soil quickly and need at least 0.25” to move them down. The best time to apply a wetting agent is in the rain! 2) The wetting agent might be due for a re-application as they are naturally degraded by microorganisms in the soil. In fact you could start using the drop test to schedule re-applications. 3) The product just isn’t doing its job and it’s time for a switch – this is actually pretty unlikely as I have tested scores of products over the years and have had very good results will just about every one.

Wetting agents remain key for managing moisture on sandy soils and I hope this tip gives you another tool to keep tabs on your product performance.

Do you have something to share about wetting agents? Share it in the comments below or on social media.