Managing Fertility inHigh-Sand-Content Greensby STANLEY J. ZONTEKDirector, Mid-Atlantic Region, USGA Green Section

ONE OF THE MOST significantchanges in golf course manage-ment during the past 30 years

has been the switch from the use of top-soil for putting green construction tothe use of materials consisting predomi-nately of sand.

This year marks the 30th anniversaryof the publication of the USGA GreenSection Specifications for a Method ofPutting Green Construction. At thetime of their introduction, these specifi-cations were considered a radical depar-ture from green construction methodsthat had endured for decades. The specs

advocated lighter, sandier soils withlower bulk densities, higher infiltrationrates, greater soil aeration and lowermoisture retention than the tradition-ally blended soil-based greens of thatday.

Prior to these specifications, greenswere typically constructed with mix-tures of sand, topsoil, and peat at I-I-I or 2-1-1 ratios. Very little considera-tion was given to the type of sand, soil,or organic matter used. Further, greenswere often intentionally underlaid witha thick layer of clay to hold water. Atthat time, irrigation systems were in their

Striping due to phosphorus deficiency!

infancy, with hose and sprinklers beingthe norm. Compaction from heavy playwas of little concern because coursessimply did not receive the amount oftraffic they do today.

These old 1-1-1 mixes were based ongeneral guidelines handed down overthe years that utilized blends of manures,composts, sharp sands, etc., all part ofthe art of putting green construction ofthat era. Sometimes they worked; some-times they did not.

The USGA Green Section specifica-tions were an attempt to put numberson the physical characteristics of a good

(Left) Sandy mixture meeting USGA specifications.(Below) Old-style topsoil-based green. Different soilsrequire different fertility programs.

quality putting green topmix. A prop-erly sized sand, with the appropriatedistribution of small and large pores, isthe key to a putting green topmix thathandles traffic and drains excessamounts of water, yet in combinationwith a small amount of soil and organicmatter retains enough moisture to growgood turf under the widest range ofenvironmental conditions.

Today, many greens built by archi-tects and builders consist only ofwashed sand and organic matter.Should these sandi organic mixes beprepared with soil to provide some siltand clay? The anwer is yes; puttinggreen mixes should contain some siltand clay to improve nutrient availa-bility, increase water-holding capacity,and help minimize the potential forsevere damage from diseases like take-all patch.

Sometimes the silt and clay are addedby way of a separate soil source. Some-times they come from the use of a dirty

2 USGA GREEN SECTION RECORD

sand or from the organic matter source.A maximum of 5% silt and 3% clay isconsidered the standard for USGA specgreens.

High-sand-content greens havebecome the standard throughout mostof the world because of their ability todrain well and resist compaction. How-ever, many golf course superintendentshave difficulty growing good turf onthese greens for several years afterestablishment. Usually, the problem is alack of understanding of the fertilityrequirements of high-sand mixes.

Maintaining Adequate Fertility Levels

How much fertilizer is enough fornew sand-based greens? This is not aneasy question to answer. Compared totopsoil greens, much greater amounts offertilizer are needed to develop andmaintain good growth on high-sand-content greens for the first couple ofyears. Much depends on how quickly

the profile drains. A green which has apercolation rate of 12 inches per hourhas the potential to leach more nutrientsthan a green that drains at 1 inch perhour. This is common sense.

Another important factor is theCation Exchange Capacity (CEC) ofthe mix. This number is often over-looked when studying a chemical soiltest and when determining how much orwhat kind of fertilizer to use on a green.The CEC is the measure of that soil'sability to hold nutrients. A soil with aCEC of 10 has twice the nutrient re-tention ability of a soil with a CEC of5. Obviously, a soil with a low CEC willoften require more fertilizer, moreapplications of fertilizers applied atlighter rates, and greater use of slow-release fertilizer than a soil with a higherCEC value.

A fertility program that works wellfor one golf course may not work thesame for another course that has adifferent soil with a different Cation

Exchange Capacity. That's why it is sohard to be specific with soil fertilityrequirements when establishing newgreens.

As a basis for comparison, straightsands with very little silt and clay oftenhave CECs of 2-3 or less. This is verylow. Sands blended with a high-qualityfibrous organic matter with traces of siltand clay often have CECs of 5-6. Thisis a common range for CECs in newconstruction. In contrast, native top-soils have CECs in the range of 12-18,if not higher. Thus, recognizing thatsoils vary in their abilities to holdnutrients provides the basis for a betterunderstanding of chemical soil testresults and formulating a fertility pro-gram for high-sand-content greens.

Nitrogen

Nitrogen use rates on new sandgreens should be high, beginning withthe seedbed. To speed the establishmentof new greens, USGA specifications

suggest 2 Ibs. of nitrogen per 1,000 sq.ft. be added to the seedbed before plant-ing - lIb. of nitrogen as a quick-releasefertilizer containing phosphorus andpotassium as well as nitrogen, alongwith 1 lb. of nitrogen as a slow-releaseorganic product.

After planting and during the initialgrowing-in phase, applications of 1 lb.of actual nitrogen per 1,000 sq. ft. perweek for at least six weeks is a commonand usually reasonable recommenda-tion. As the grass matures, rates andfrequencies should be reduced. None-theless, the first year totals for nitrogenin new greens could well seem ridicu-lously high compared to maintenancefertility levels for mature greens.

After the green has matured,maintenance fertility levels in sandysoils are typically about ~ lb. of actualnitrogen per 1,000 sq. ft. per growingmonth. This can vary due to severalfactors like CECs, infiltration rates, theamount of irrigation! rainfall, traffic,etc. To some, this may still seem like too

much nitrogen, especially when ultra-light fertility programs in vogue a fewyears ago are recalled. While it is truethat older topsoil-based greens can stillbe fertilized at low rates, this is not thecase for new sandy soils. More nitrogenis needed, especially during the initialphase of new putting green establish-ment. In fact, the lack of adequatefertility is one of the most commonproblems in the maintenance of newsand-based greens.

All too often the grass establishes asit should and then, after the initialgrowth slows, the grass becomes thin,shallow rooted, and stalky. These aresigns that the green has run out offertility.

Phosphorus

For years, we have been told thatphosphorus is not needed on puttinggreens. Soil tests often show excessivelevels of phosphorus, and besides, wewere warned that high levels of

Poor mixing of a sandi peat green only complicates fertility management.

When moss grows better than the grass, you know you've got afertility problem.

phosphorus stimulate Poa annua. Thismay be true with golf greens constructedof topsoil, but the story changes whendealing with soils composed predomi-nately of inert sand. The fact is, grassneeds phosphorus. Topsoils can be richin phosphorus, but sands are not.Further, while phosphorus is not mobilein heavier-textured topsoils with theirnaturally higher CECs and slowerdrainage rates, phosphorus can move insands with their much lower CECs andrapid drainage.

Do not forget phosphorus. As ageneral guideline, 2-3 Ibs. of actualphosphorus per 1,000 sq. ft. per year asa maintenance fertility level is reason-able. Also, high phosphorus "starter"fertilizers are recommended duringestablishment. These fertilizers shouldbe raked into the seedbed. Thereafter,periodic soil tests should let you knowfor certain the extent to whichphosphorus needs to be applied to sand-based greens.

By the way, the link betweenphosphorus and Poa annua stimulationis exaggerated and is secondary to theneed to grow a strong, healthy stand ofturfgrass. The best weed control, in-cluding Poa annua, is to develop a densestand of grass. Proper fertility shouldprovide the density which helps containthe Poa annua. Sandy soils need ade-quate phosphorus fertilization.

Potassium

Recent research, in conjunction withfield observations, is showing just howimportant it is to maintain adequatelevels of potassium in sandy soils.Potassium is nearly as prone to leachingand luxury consumption as nitrogen. Insandy soils with low CEC values andhigh percolation rates, potassium needsto be applied at nearly the same ratesas nitrogen. Since most sandy soils arenaturally low in potassium, a ratio of 1.5Ibs. of potassium to every 1 lb. ofnitrogen applied during the growingseason is not unreasonable. Fieldexperience and periodic soil tests (atleast once per year) should helpdetermine adequate potassium levelsand application rates.

One final point. Because grassexhibits luxury consumption of bothnitrogen and potassium, periodicapplications at light rates are preferableto infrequent applications at heavierrates.

Soil Reaction - pH

Maintaining soil pH in a reasonablerange is recognized as being importantby all turfgrass managers and scientists,regardless of the type of soil. This canbe a special challenge in sandy soils,with their inherently low CECs and low

soil buffering capacity, especially whenthe greens are young. Big swings in soilpH and nutrient levels are common innew greens. Fortunately, these peaksand valleys tend to soften as a greenages. For example, the addition of asmall amount of elemental sulphur canradically change the pH of a new sandsoil. Strive for a middle-of-the-roadapproach to pH management. Main-taining pH in a range between 6.0 to 7.5is reasonable and is no great cause forconcern, especially during the first fewyears following a green's construction.

Also, when soil tests are done, includethe test for buffer pH. Standard pHtests tell you the pH of the soil solution,whereas the buffer pH is more repre-sentative of the true pH of that soil. Arainfall can affect the pH of the soilsolution, but it will not change thebuffer pH.

Low pH levels should be slowlyraised by light applications of lime,never exceeding 25 Ibs. per 1,000 sq. ft.per application. Lighter rates appliedmore often is preferred to burying thegreens in lime.

Similarly, pH values above 8.0 shouldbe managed carefully and slowly withsulphur or, better yet, fertilizers whichnaturally create acid as they breakdown. The Calcium Carbonate Equiva-lent on every bag of fertilizer is one wayof measuring how much acidity iscreated by that particular fertilizerproduct. If the bag states 640 Ibs.Calcium Carbonate Equivalent, then ittakes that amount of lime to neutralizethe amount of acid that is formed by thefertilizer. On high-pH greens, you canuse this value to good advantage inlowering pH without running the risk ofburning the turf, which sometimes canoccur with granular applications ofelemental sulphur.

In my opinion, the use of elementalsulphur to lower soil pH levels can beoverdone, especially if the sand used inthe original construction of the green iscalcareous. Lowering the pH level inthis type of soil can be an exercise infutility. Yes, you can change the pH ofthe soil solution, but it is nearlyimpossible to overcome a high bufferpH soil such as those constructed withcalcareous sands. The best advice tosuperintendents who must deal withcalcareous sand greens is to learn to livewith it. Keep a close watch on nutrientlevels in these greens, especially iron,and make adjustments accordingly.

This is an important point to considerwhen choosing a sand for new con-struction or topdressing. Hard rock or

4 USGA GREEN SECTION RECORD

silica-based sands, which are nearlyneutral, are preferred over high-pHcalcareous sands. Sometimes there is nochoice. However, if there is a choice, thelong-term management of nutrients andsoil pH is far easier in neutral or slightlyacid soils than in high-pH soils.

Micronutrients

Much has been said about the valueof micronutrient applications on high-sand-content soils. Actually, the onlymicronutrient deficiency in sand-basedgreens that we have identified in thefield is for iron. This problem is worsein high-pH sand greens, where ironavailability is poor. Beyond this, evi-dence suggests that heavy use of micro-nutrients probably is not needed. Pru-dence would suggest, however, that insandy soils with low CECs, micro-

nutrient applications be made periodi-cally to satisfy micronutrient require-ments. Again, the exception is iron,which should be applied lightly and ona frequent schedule.

In Summary

In the past decade or so there hasbeen a trend in our industry toward lowlevels of fertility on golf greens. Onolder topsoil-based greens, about 2-3lbs. actual nitrogen per 1,000 sq. ft. peryear has been successful in many in-stances. It should be appreciated thatthese low fertility levels are best utilizedfor topsoil-based greens and not sandgreens. Extremely low fertilizer ratesare not appropriate for the growing-inphase of new golf greens or for theirfollow-up maintenance. This is why somany turf managers are hesitant to

apply enough fertility to new greens;they simply are not accustomed toapplying that much fertilizer!

Look at your new greens. Do theyhave good roots, good density, reason-able color, and a developing thatch layerfor good resiliency? If so, then youprobably are on the right track.

By contrast, is the grass shallow-rooted, thin, coarse bladed, prone tospike marks, and speckled with invad-ing Poa annua? Does the grass lackdensity, color, and an appreciable thatchlayer? If this is the case, then yourfertility program may be too low.

Consider all of these points. If you dohave any questions, call your localUSGA Green Section agronomists foradvice. Once you become accustomedto the higher rates of fertility requiredby them, sand greens become far easierto manage than the old greens theyreplaced.

Environmental Fate ofCommon Turf Pesticides -Factors Leading to Leachingby DR. KARL H. DEUBERTUniversity of Massachusetts, Cranberry Experiment Station, East Wareham, Massachusetts

PESTICIDE users make a pre-carious decision every time theyapply a chemical: Will residues of

the chemical contaminate the ground-water or not? To complicate the situ-ation, there is little information avail-able to make such a decision and toguarantee its accuracy. Manufacturersare reluctant to elaborate on this.Scientists use predictive models to makeeducated guesses about potentialresidue movement. Though models arebased on defined environmental factorsrarely found in the same combination inthe field, they remain the best availabletool to assess the potential of a chemicalfor contamination of groundwater.

Most models are based on results ofstudies done in relatively small geo-

graphic areas. Consequently, they aremost useful in areas for which they weredeveloped. In other areas, differentfactors and combinations affect theaccuracy of the results. Most important,the interpretation of results requiresexpenence.

Despite considerable amounts ofavailable information, the simplequestion, "Will compound X, when Iuse it, contaminate groundwater?" isdifficult to answer. To illustrate thepoint, a sophisticated model was chosento suggest which of the compounds thathad been used in the past on several golfcourses on Cape Cod might have con-taminated groundwater. The computerselected dicamba and suggested that

chlordane would remain in the topsoil.Ironically, chlordane was found inwater samples (GCI MS analysis), anddicamba was not. This is an extremeexample and is not intended to discreditthe use of models.

However, the user needs an answer,and there are situations where quickanswers are needed to as'sess the poten-tial for groundwater contamination. Inthese cases, good knowledge of localsoil and weather conditions (environ-mental factors) in combination withsome basic information about thechemicals involved (compound-relatedfactors) provides the basis for a quickand reasonably good assessment of afield situation.

JULY/AUGUST 1990 5