ManagingSoilWaterbySTANLEYJ.ZONTEKDirector, Mid-Atlantic Region,USGA Green Section

Algae growth occurs on wet, saturated soils, and indicates a problem that needs attention.

W!?tN it comes to managing turf,anyone even remotely in tunewith basic agronomics recognizes

that putting greens with wet soils are goingto cause problems. Equally, golfers know thatsoft greens, while they may hold a golf shotwell, do not play very well. They tend to besoft underfoot, which equates to bumpy anduneven putting surfaces that are more proneto spike marks. Wet greens also seem to puttslower than fIrmer, drier greens.

The Green Section's agronomists certainlyappreciate the problems associated with wetsoils in greens. In fact, in a survey of thestaff, they listed wet and overwatered greensas the highest-rated agronomic problem inmanaging putting green turf today.

The agronomic problems associated withwet soils in greens are not lost to golf coursesuperintendents, either. They know all toowell that wet, saturated soils are more proneto compaction and result in turf with shallow,weak root systems. Poa annua and otherweeds tend to be more of a problem in wet,soggy soils, and outbreaks of many diseasescan be far worse. Greens that hold waterusually are a superintendent's indicatorgreens. That is, if a problem is expected, itwill appear fIrst on a wet, pocketed green.Rarely do greens die from a lack of water.

The question is, what can be done aboutit? How does one manage greens which,once they become wet, stay wet, and howdoes a golf course superintendent manageexcess water in the soil?

By understanding the fate of water in thesoil, the golf course superintendent can bet-ter manage soil water. The result is bettergrass with fewer chemicals, and fewer grassfailures. Knowing how to manage soil wateris an important aspect of establishing anIntegrated Pest Management (IPM) program.

Sources of Water in the Soil

The perception exists today, and has foryears, that wet greens are almost exclusivelycaused by overwatering. The thinking is thatmost golf course superintendents overirri-gate on purpose since many golfers like softgreens and overwatering is easier than properirrigation management. I submit that, likemost generalizations, this one is unfair to themany superintendents who irrigate withgood common sense. At one time, someyears ago, this overwatering criticism mayhave been true. Today, with greater knowl-edge, better technology, and an awareness ofthe problems associated with wet greens, turfmanagers as a group are more careful thanthey ever have been in keeping greens as

dryas possible. Good water control isrecognized as a major management goal oftoday's golf course superintendent.

The question is, why do wet greens stilloccur? In particular, why do there continueto be wet soils on shaded, pocketed greens?To answer this question, the source of waterin the soil needs to be examined.

Water in the soil generally comes fromtwo sources, rainfall and irrigation. With golfcourse superintendents being better attunedto the problems of wet greens, and with thebetter irrigation systems we have today, theapplication of water onto greens should notbe the main source of the problem.Obviously, problems still occur with over-watering, but the fact is, most golf coursesuperintendents try not to overwater greens.They are doing more and more handwatering, especially on poorly drained,pocketed greens. But some years thisprogram is less successful than others. Why?The answer lies with the second source ofsoil water - rainfall.

All things being equal, problems withgreens occur much more often during wetyears, especially when the rainfall occurs inconjunction with hot, humid summers. Thereason is simple. During dry years, thesuperintendent has control of the water.

SEPTEMBER/ OCTOBER 1994

Poor syringingtechniques result inpoor water control.Runoff should never

occur when twf isproperly syringed.

When superintendents lose control of waterin the greens, their troubles begin. Soilsbecome wet and saturated; they become an-aerobic and black layers can form; roots dieback; the grass becomes weakened. Then,disease and other problems occur (includingalgae, brown patch, and damage fromvarious Pythium species). Inextreme cases,wet wilt can occur. In the meantime, golfcontinues to be played, the greens continueto be mown, and the soils become compactednear the surface. Problems accelerate as theturf thins, algae invades the voids, and thesuperintendent loses control of the situation.

Given this potential scenario, most super-intendents I know prefer dry years. Theysimply have better control over the water ontheir golf course. Superintendents dread wetsummers on soils that do not drain. Theyknow that once the soil is wet, it is hard todry it out. The question is, where does soilwater go and how can soils that are wet bebetter managed?

The Fate of Water in the SoilOnce water has entered the soil, two things

can happen to it. They are:1. Drainage - Excess water moves down

through the soil profile.2. Evapotranspiration - Water is lost into

the air from the turf surface through evapo-ration from the soil and transpiration fromleaf surfaces.

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It is very important to know and appre-ciate each of these fates. They are the meansby which the golf course superintendent canmanage excess water in the soil. Let's lookat each one.

1. DrainageIt's an unfortunate fact that the majority of

the putting greens in this country do notenjoy anything approaching rapid internalsoil drainage. In fact, most golf greens in thiscountry were not built with even a basicsystem of drain lines, much less on a gravelblanket. They would be characterized ashaving varying types and depths of soil;many are old-style, clay-based greens whoseonly salvation is having good surfacedrainage. And where soil modification mayexist, it usually occurs only to the depth ofthe aeration holes or the topdressing layer.

Also, only a small minority of puttinggreens have a modified root zone throughthe entire soil profile down to a gravelblanket or to drainage lines. It is even asmaller percentage of putting greens that arecarefully built to any recognized specifica-tions for putting green construction, be theyguidelines from the USGA Green Section orelsewhere. This is where most of the pr9b-lem lies. Even though superintendents mightbe very careful when irrigating their poorlydrained greens, water control is lost when

rainfall occurs or in instances where over-watering does occur. Once wet, these greensremain wet, and when you combine wet soilswith hot temperatures, the vicious cyclebegins.

2. EvapotranspirationThe loss of soil water by evaporation from

the soil and transpiration from plant leaves istermed evapotranspiration. Transpiration isthe mechanism by which most of the evapo-transpirational water is lost from denseturfgrass stands, including most greens. Asmuch as 80 to 85 percent of soil moistureloss can be attributed to evapotranspiration(Beard, 1973).

The evapotranspiration rate (ET) is a well-known number used by many golf coursesuperintendents when scheduling their irri-gation programs. Unfortunately, the amountof water lost through evapotranspirationfrom a golf course varies from site to site andfrom green to green. For example, a greenlocated in shade, without good air circula-tion, will lose much less water from the samesoil than an adjacent green located on top ofa hill with good air circulation and full sun-light.

It is in situations like this that theexperience and expertise of golf coursesuperintendents are tested the most. That is,the management of the amount of water

applied to individual greens. Differentmanagement strategies must be employedwhen irrigating grass on a green in oneenvironment compared to greens in otherlocations.

On some courses, most greens requireseparate irrigation programs. Managingthese differences remains one of the greatestchallenges for today's golf course superin-tendents. If overwatering of greens occurstoday, this is where it can happen. Whengreens growing in different environments areirrigated according to the same schedule, nodoubt some of these greens are being under-watered or overwatered.

If there is an overriding purpose to thisarticle, it is to point out how water reachesthe soil and how it then moves out of thesoil. Sometimes, I feel we look at eachelement - irrigation, drainage, and evapo-transpiration - as a separate item. In reality,they are intimately associated.

Managing Soil Water

What are the tools available to the golfcourse superintendent to manage soil water?

1. Irrigation Management

Irrigation is the intentional application ofwater to the turf and soil. Determining howmuch water to apply to a given green on agiven day is one of the most profound chal-lenges facing a golf course superintendent. Ifa green has a sandy, modified soil over agravel drainage blanket with a completedrainage system underneath, the bestirrigation program will be different from thatpracticed on an old-style, clay-based push-upgreen. On these old greens, the only well-draining soil is what has accumulated, overtime, through aeration and topdressing.

Managing soil water begins with properirrigation. Simply appreciating the differ-ences in the soil's ability to drain or holdwater is critical to exercising water control,whether it is for a green on top of a hill orunder a tree. This is why more and moresuperintendents are installing separate irri-gation systems for their greens and greenbanks. This is a good way to separate thewater needs of a green from those of thesurrounding areas, which often require morewater than the green surfaces themselves.

More and more greens are being wateredby hand. This is a very effective tool for thegolf course superintendent. Perhaps there isno better money spent on a golf green thanfor hand watering. It provides for improvedwater control, pure and simple. On poorlydraining soils or on greens that are shadyand have a lower ET rate, try to irrigate onthe side of dryness. Youcan always add morewater; it is tougher to remove the excess.These strategies work, at least until itrains!

2. TopdressingTopdressing is the addition of a better

draining root zone material on top of theexisting green. A deeper zone of modifiedsoil allows the superintendent to bettermanage compaction, turf root development,soil water, and drainage, at least to the depthof the modified zone. Many greens on oldgolf courses have been sufficiently modifiedby topdressing over the years to drain ade-quately, especially where surface drainagealso is adequate.

Dense trees prevent good air movement and dramatically reduce evapotranspirationfrom the tUlf Greens that hold too much water tend to be plVblem greens.

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still expect good grass on these greens. Whenthis occurs, the best option may be a fan, orfans, installed at the green site.

The most -asked questions about the use offans include:

Will a fan compensate for the lack ofsunlight?

No.Will a fan help move water out of wet soil?Yes.In fact, a fan could be the golf course

superintendent's last opportunity to manageexcess water in the soil. It allows a wet greento dry out in situations where the green tendsto stay too wet for too long.

Summary and ConclusionManaging soil water includes providing

good surface drainage, whenever possible, tomove excess water away from the site.

Managing soil water includes managingthe application of irrigation water onto thesite.

Managing soil water includes providinggood aeration and drainage to move waterthrough the soil.

Managing soil water includes a good top-dressing program to modify an existing soilwith a better-draining material.

And [mally, managing soil water includesmoving water out of the soil via evapotran-spiration.

All too often today's golf course super-intendent is being indicted, sometimes un-fairly, for having wet greens. In reality, inmany different situations and in many partsof the country, the superintendent reallydoes not control soil water because of ex-cessive rainfall, slow-draining soils, and/orinsufficiently built or layered greens builtof modified soil.

Whether a putting green becomes overlywet due to rainfall or irrigation, the golfcourse superintendent must manage theproblem. It was the purpose of this articleto help the turf manager understand theproblem, consider all options, and developshort-, intermediate-, and long-term practicesto help manage water in the soil. After all, ifyou can manage soil water, you can bettermanage grass growing in the soil. It is whenyou lose control of soil water that problemsdevelop.

With a good appreciation that managingsoil water involves more than just irrigation,programs and procedures can be put intoplace to solve these problems to producebetter grass. If, however, all of these tech-niques fail to provide reliable turf, the [maloption for improving your ability to managesoil water is complete reconstruction.

Reference:Beard, James B. 1973. Turfgrass: Science andCulture. Prentice-Hall, Englewood Cliffs, NJ. pp.658.

4. EvapotranspirationHave you ever wondered why the installa-

tion of oscillating fans on golf courses is sucha rage today? It really is the result of severaldifferent, yet interrelated factors. Basically,fans significantly increase evapotranspira-tion, or the movement of water out of thesoil. Fans are never installed around a greenthat is located in complete sunlight andreceives good air movement. Fans are onlyused on pocketed greens that lack good aircirculation. They are a mechanical means ofincreasing evapotranspiration and dryingout the soil. Today, fans are one of the newestand best methods available to the golf coursesuperintendent to maintain turf on enclosed,pocketed, and shaded greens.

We all know that one of the major prob-lems facing golf course superintendentstoday is the difficulty of convincing courseofficials to cut down trees for more sunlightand better air circulation on pocketed greens.It has been recognized for years that theweakest greens and tees on most golf coursesare those located in these areas. People arereluctant to cut the trees, prune limbs, andremove underbrush necessary for good aircirculation, sunlight penetration, and a bettergrass-growing environment. However, they

If trees can't be removed, a fan is the superintendent's last hope to increase air movement.- .. '}..-r:~

), .~.

3. AerationGreat strides have been made in soil aera-

tion equipment during the past 10to 15years.Machines can now aerate deeper than everbefore, produce more holes of different sizesand shapes, and do the job more quickly thanever. We can even aerate soil without com-plaints from golfers by using solid tines,traditional spikers, or high-pressure waterinjection.

All of these devices were developed,really, for three purposes:

1) to improve water infiltration,2) to relieve soil compaction, and3) to allow holes to be backfilled with a

better quality material for improved soilaeration.

This is managing soil water at its best.Good aeration creates pores that provide anavenue for water to move through the soil.Also, aeration is a method of drying out awet soil once it becomes saturated. Aeratingin the heat and humidity of a summer stressperiod might seem extreme to some, but if ithelps to keep a green alive, it is worth it.There is always some risk involved, butusing a small coring tine, a solid tine, an oldspiker, or a new water injection machine canminimize the risk.

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