Irrigation - as the dry spell continues, questions arise as to why and how we irrigate. Below is a recent posting by Ben McGarill, the superintendent from Wynstone which does a great job of answering this question (FYI - he is an Iowa State graduate, so he knows his stuff!).
Posted: 12 Jun 2012 03:04 PM PDT
During dry periods, we often hear the questions, “Why do you guys hand water? Didn't we just install a new irrigation system?”
The answers to those questions are like of lot of answers we give. There are a variety of factors involved, and there is never a single factor that allows for concrete decisions on how much water to apply with the irrigation system. Our goals are relatively simple; turf health and proper golfing conditions. With those two things in mind, golfers and turf managers would agree that over-watering would be the wrong thing to do, although we sometimes make that mistake.
One thing to keep in mind is that irrigation is a supplement to rain. You and I might drink a Gatorade or take a multivitamin, but these things will not serve as replacements for water and food. The spring of 2012 was considered a very dry season right out of the starting gate. We have seen many days in which evapotranspiration (ET) has reached .25”. In other words, one quarter of an inch of plant available water disappears through both evaporation and transpiration of the plants. Not only would it be impossible for us to replace this amount of water in the overnight hours, it would also create very soupy conditions in the top two inches of the soil profile if we tried. So during drought periods, we operate at a fairly significant deficit.
Another thing to consider is the manner in which the soil accepts the water that is applied. Perfect coverage and infiltration is not possible. If the golf course was perfectly flat, had a uniform soil type, identical internal drainage throughout, and only one grass type, we may be able to get close. There is still one problem though. Irrigation heads throw in a circular pattern; not a square pattern. Today’s irrigation systems do get us much closer to uniform coverage than yesterday’s, but it is unlikely that you and I will see 100% uniform coverage in our life time.
When you see someone hand watering a “knob” in a fairway or a high shelf on a green, it is safe to assume that if we had watered enough with our irrigation system to make that particular spot wet, the low areas around it would be entirely saturated or may even have standing water in them. I encourage you to embrace our firemen and the hoses that we drag around, because it makes for better growing conditions and better playing conditions. And remember, a little brown turf is not the end of the world as long as it isn't because it is too wet. Dry and brown will often recover very rapidly. It is amazing what an inch of rain will do, even after a dry spell.
|Can you figure out where the turf is watered the most and least? The same issue occurs with sprinklers around greens. If only we could water in a square.|