June 14, 2010 By Mike Jiggens
By Sean Jordan, T.Ag., Agronomist
IN the April/May issue of Turf and Recreation, I wrote what could be
considered a sequel to the story in the previous issue called “A Hot
Summer.” For those of you hoping for a trilogy, it just isn’t going to
happen. I will leave that up to the guys with real talent like Lucas
and Spielberg. Instead, I would like to expand upon one idea that was
discussed relating to surviving summer heat: managing your irrigation.
With many predicting a summer of higher-than-average temperatures and less precipitation than we have seen the past two years (which would not be difficult), irrigation is on the minds of many superintendents.
In much of Ontario, we have experienced one or more dry periods already this spring, causing a mad rush to “fire up” irrigation systems and keep turf alive long enough to see summer play. Having been caught in this situation of trying desperately to put water on my greens with anything short of a bucket from the creek, I am well aware of the importance of planning the irrigation start-up before it becomes critical.
This is not to suggest starting so early that water is running through the pipes while the ground is still frozen, but rather making sure that all the pieces are in place before irrigation becomes a limiting factor in the turf’s survival. By the time the irrigation blowout comes in late fall, it is natural tendency, brought on by sheer exhaustion, to want to leave the broken bits until spring. All too often this comes back to bite us as it is easy to forget, after a long winter’s nap, all that has to be done. Even if all that is accomplished in the winter and early spring is the creation of a “to do” list and the accumulation of the necessary parts, managers will still be ahead of the game.
Now, with winter a distant memory, it is necessary to address the task at hand. I spoke briefly in the last article about irrigation regimes that relate the amount and delivery mechanisms to the state of the rootzone and will explain here some of these ideas in more depth.
There are tools available that are fairly inexpensive and can provide plenty of information about what rootzones are experiencing. As an assistant in the mid-Atlantic region of the U.S., I was expected to have a soil probe pretty much glued to me at all times in the summer to gauge where and how much water was needed. Pulling a core from the soil and judging the moisture content and status of the roots is an invaluable technique and fairly easy to learn with some patience and good observational skills.
I was fortunate to have worked with a superintendent who enjoyed teaching as much as he did growing grass. He would have me feel cores from particular areas in the morning or early afternoon, already knowing from experience what I would see. I was to revisit those areas throughout the day to see what happened to the turf as temperatures increased and humidity changed.
Another such simple tool for monitoring irrigation needs is a soil thermometer. There is a great deal of information available in books and articles on Michigan State University’s Turfgrass Information File (TGIF is available to most CGSA members through the website) on soil temperature and the physiological effects it has on turf plants. As with a soil probe, the use of a soil thermometer is something that becomes more beneficial with experience. With either tool, however, one point to keep in mind is that any information you gather with these tools is going to be from a small area, making it necessary to step back and look at the whole area to ensure that nothing is being overlooked.
When judging the method with which to apply the necessary water to the turf, it can be very easy for the “heat stressed” manager to use sprinklers instead of a hose for sake of man-hours or trying to stay ahead of play. This creates a vicious cycle where time to apply the proper amount of water is sacrificed, and a need for more intensive management becomes necessary due to damage done to the plant in haste.
Irrigation systems, for all of the technology that goes into their development, are simply meant to water given areas of turf and lack the ability to differentiate between sufficiency and need within those areas. Don’t get me wrong. A well-designed irrigation system is second only to Mother Nature for applying water efficiently in a relatively short period of time. Rather, include the hose connections in those irrigation systems to appropriately manage areas with special needs.
When it comes to dragging hose, it is important to make the distinction between the two general methods employed—hand-watering and syringing—which are two very different practices. Hand-watering is irrigating specific areas to supply water to the plant. This is done where there are issues with localized dry spot, slopes and undulations and limited water-holding capacity of the soil or other special circumstances such as repairs that dictate a need for supplemental irrigation.
Syringing, however, is not meant to supply water to the plant; it is meant to cool the turf surface through evaporation. A way of explaining proper use of this technique, which I learned from a former intern at Augusta National, proved very useful for training my own staff in the past: “Place a paper towel on the green. Walk quickly across the green with the hose pointed upward so that only a light mist falls on the turf surface. Pick up the paper towel. If the turf under the paper towel is wet, too much water was applied.”
Many managers with whom I have shared this technique argued the practice, saying that not enough water is being applied and it would require constantly making circuits on the course to keep up. I did not argue, as there were many days that I spent making the rounds on greens just to have to do it all over again. However, the point of this method is to help cool the grass plants on days of intensive heat when the turf just can’t transpire enough for sufficient cooling and wilt occurs. The importance of this specific technique can be justified when the effects of wilt are seen, even in soils where moisture is adequate.
Roots are excellent indicators of how much water to apply and when. It is a natural occurrence for turf root mass to decline during periods of high temperatures. At temperatures higher than optimal for each turf species, grass plants start consuming more resources than can be produced by photosynthesis. This results in a net loss to the reserves that have been stored up in the roots since the previous fall.
In addition, these sustained periods of high soil temperatures cause the reduction of root mass and length in cool-season grasses. Knowing that the roots will be less efficient and shallower is half the battle; irrigating to accommodate that fact is the other half. If, through any number of factors—temperature, root diseases, and root-eating insect pests—the turf has been left with a less-than-par root system, more frequent and shallower irrigation regimes may need to be implemented as deep and infrequent watering can leave the not-so-deep roots seeking water that is out of reach. It may also be the case that the two basic schools of thought should be combined on the same turfgrass area if only a portion is affected.
Summer stress is a given and managing that stress is all part of the art of turfgrass management. Gathering as much information as possible from the turf about what it needs will help limit the amount of stress endured by both the turfgrass manager and the turf on which they stand on.
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