I've said it before, but in my opinion, properly irrigating the course is the most difficult and most important task that we tackle throughout the season. When making irrigation decisions, we essentially try to balance plant health with playability and the two are often competing forces. Add in the ever-unpredictable weather, and it becomes even more challenging. I think that most turf managers would agree that irrigation is a combination of science and art.
In the past, it may have been more art than science, and irrigation decisions were often based on cutting into the soil to essentially feel the moisture. This feel method, coupled with observing the turf and checking the forecast, was much of the basis for irrigation scheduling, and experienced turf managers became very, very good at it. To some degree, I believe that you still have to incorporate these "old school" methods to irrigate properly, but over the years, scientific tools to evaluate soil moisture have become much more common. These tools provide specific numbers to make the most well-informed decisions that we can. At Blackhawk, we've owned a soil moisture probe for about four years, but until 2012, we quite frankly didn't use it as often as we should have.
On 34 days from June 6-August 7, nine soil moisture readings were taken and recorded on each green. These readings were almost always taken between 8 and 9 am, and they were used to identify areas that likely needed supplemental irrigation in order to make it through the day. As a baseline, any areas that were below 20% volumetric water content were hand watered in the morning to get them to that level. While this didn't eliminate the need for hand watering dry spots during the afternoon (thanks to the Poa annua roots that melted in the heat), these readings did reduce it and are one of the reasons why the greens did so well throughout this extremely hot and dry summer. Besides aiding us this past summer, the readings that we collected will help us to improve the course in 2013 and beyond.
As you can probably imagine, irrigation systems are far from perfect (circular rotation set in a square pattern), and greater than 80% distribution uniformity (DU) is considered excellent for overhead irrigation. To compensate for differences in shade and slope, each of our irrigation heads have a percentage adjustment on them to deliver the appropriate amount of water. In the end, it is our goal to have consistent soil moisture levels across on each individual green and across the greens as a whole. This winter, I entered the 5,508 soil moisture readings that were recorded in 2012 and did a quick and dirty analysis of the numbers to see how we did.
Across the course (using every data point), we achieved 83% soil moisture DU. The DU of individual greens ranged from 82-92% and averaged 87%. Given the many microclimates that the course has and the severe slopes that are present on many greens, I would say that we did pretty well, but we've also identified several areas that we can make improvements on. Although it may take a few years of data collection and adjustments, I see no reason why we can't get above 90% across the board. Since the soil moisture of greens plays a tremendous role in determining the speed and firmness of greens, these adjustments will greatly benefit you, the golfer.
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