TODAY'S LESSONSProper soil sampling

Consistent use of labsSoil pH near neutral

Seek help from expertswhen necessary

"". -

Soil Fertility andTurfgrass Nutrition 101Some important concepts you might have missedin or outside of the classroom.BY JAMES H. BAIRD

Few would dispute that there are both an artand a science to growing high-quality turfHowever, these days it seems that soil

fertility and turf grass nutrition practices arebecoming less scientific and more illogical thanartistic.

While science continues to move forward,it appears to me that most of the new theoriesor so-called advancements are professed bycompanies or individuals who stand to gain byselling their products or consultation services.Most turf managers won't hesitate to apply anew product if they believe that it won't hurtanything and could only help their situation.Unfortunately, applying the wrong nutrient or

too much of a nutrient can result in deficienciesof other nutrients, greater potential for diseaseoutbreak due to changes in soil acidity, orperhaps unfavorable changes in soil physicalproperties. Given today's uncertain economyand increased scrutiny over chemicals applied inthe turf grass environment, all turf managersneed to re-evaluate their fertilization practicesby using science as the foundation upon whichpersonal experience and feel are built.

Soil fertility and plant nutrition are complexsubjects, but they're far from incomprehensible.An article of this length cannot begin to addressall of the basic principles of soil fertility and turf-grass nutrition. Rather, the objective is to help

SEPTEMBER-OCTOBER 2007

Table IGeneral trends of soil pH on nutrient availability and various turf problems.

<5.0 5.5 6.0 6.5 70 7.5Deficiency «5.5)NitrogenPhosphorusPotassiumMagnesiumMolybdenumSulfur

Disease (>5.3)Spring dead spot

Disease (>6.0)Summer patch

Disease (>6.5)Pink snow moldTake-all patch

Deficiency (>7.5)PhosphorusIronManganeseBoronCopperZinc

AI, Mn ThatchToxicity I Accumulation«5) I «5.5)

I

simplify several concepts that are critical toensuring turf health and both environmentaland fiscal responsibility. Emphasis will be placedon soils and turf grass nutritional needs in theNortheast, although the principles will applymore broadly. For more information, please seethe references that follow. Let's begin our lesson.

TAKE CHARGE OF YOURSOIL TESTING PROGRAMBefore applying any nutrient, it's important todetermine which ones are deficient and in whatamounts. Nutrient deficiencies, including nitro-gen (N), iron (Fe), and phosphorus (P), aresometimes visually detectable to the well-trainedeye, although quantification of the supplementalamount required is difficult if not impossible.Tissue testing provides a much more objectiveand quantitative evaluation of the nutritionalstatus of the plant. However, more research isneeded to correlate nutrient levels in tissue withturf grass response. Tissue testing is best used as adiagnostic procedure since a plant must be undernutrient stress for a deficiency to show.

Although far from perfect, soil testing remainsthe most common and best method of determin-ing the nutrient availability to the turf grass plantsince it attempts to identify potential problemsbefore they occur. Judging by the number ofturf managers who hire soil consultants or thenumber of times I have been asked to interpretreports, I gather that many turf managers are

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N (urea)Volatilization(>7.5)

uncomfortable with deciphering soil test results.In the reference section, several articles addresssoil testing in one capacity or another. Thefour principal components of soil testing are:1) sampling, 2) laboratory analysis, 3) interpreta-tion of results, and 4) recommendations forchemical changes, if needed.

DON'T UNDERESTIMATE THEIMPORTANCE OF PROPER SAMPLINGImproper sampling for soil testing can be one ofthe greatest sources of error in soil testing pro-grams. A few things to keep in mind about soilsampling are: 1) take at least 20 sub-samples(cores) of a representative area to be pooled,mixed, and sampled for testing; 2) sample at auniform depth (e.g., usually 2 to 4 inches forputting greens; 3) if a true thatch or topdressinglayer is present, consider subdividing each coreinto thatch or mat and underlying soil todetermine chemical and nutrient properties ofeach component; and 4) sampling time andfrequency are important for determiningconsistency of test results and effectiveness offertilizer applications. Chemical changefollowing fertilization can occur within days orweeks in sandy soils compared to months oryears in clay soils. In the Northeast on sand-based greens or tees, consider sampling in spring,prior to aeration, and again 6-8 weeks afterfertilization with granular formulations as afollow-up analysis. Sample once again 6-8 weeks

Soil test results are likelyto generate verydifferent results when samples are taken atvarying depths. In the case of a longer soilsample, separate and analyze the uppersandy portion of the profile separately fromthe mineral soil below.

ESSENTIAL NUTRIENTS

SOLUBLE SALTSMeasurement of soluble salts is especiallyimportant for determining salinity onsalt-affected soils. Electrical conduc-tivity (ECe) is reported in units ofdecisiemens/meter (dS/m) or milli-mhos/centimeter (mmhos/ cm). AnECe above 4.0 dS/m is consideredsaline. The saturated paste extract(SPE) is considered to be the standardprocedure for measuring ECe, sodiumabsorption ratio (SAR), and boron (B)concentration. Although not typicallyreported on a test in the Northeast, theSAR is a measure of the potential forexcess sodium (Na) to cause structuraldeterioration of soil. SAR levels above12 are considered problematic for soiland plant health, whereas ideal levelsshould be 3 or lower. If soil tests revealproblems with soluble salts or Na, it isimportant to have the water sourcetested and seek help from a qualifiedconsultant or university specialist.

instead used by the lab to determine liming raterecommendations, when necessary. The abilityto lower pH of alkaline soils with the addition ofsulfur or acid is largely dependent upon free limepresent in the soil, with higher quantities pro-viding greater buffer capacity against pH change.Thus, it is not recommended that pH reductionbe attempted in soils with even a lowpercentage of lime due to the verylarge acid quantities required and thepotential for turf injury.

Laboratories use chemical extractantsto estimate the levels of soil nutrientsthat are readily available to plants.Values are reported in parts per million(ppm) or pounds per acre (lbs/ A). Inaddition, most labs will categorizeeach nutrient in terms of availabilityto the plant from below optimum toabove optimum, or very low to veryhigh. This method is referred to as thesufficiency level of available nutrients (SLAN),which attempts to correlate plant response toextractable soil nutrients. Although it could besaid that there are limited data directly correlat-ing soil nutrient levels with specific and desirable

BE CONSISTENT WITHLABORATORY ANALYSESSeveral university and commercial laboratoriesare available for soil sample analysis. Be cautiousabout analyses and recommendations that areoffered free of charge from fertilizer manufac-turers or turf distributors. Also, it is important toknow that results are likely to vary from labora-tory to laboratory due to different extractionmethods and chemicals used for analyses. See thearticles by Carrow et al. (2003 and 2004) thatdescribe differences among soil analyticalprocedures. For the sake of your soil testingprogram, it is important to choose a laboratorythat uses procedures and nutrient ranges thatare appropriate for the soil types on your golfcourse. Once that information is gathered, theimportant thing is to use the same laboratoryyear in and year out to analyze trends in nutrientavailability and deficiencies.

following aeration and fertilization in latesummer.

YOU TOO CAN INTERPRETA SOIL TEST REPORTInterpretation from the laboratory or a consultantaside, every turf manager should feel comfort-able with understanding soil test results. Thefollowing is a description of information likelyto be found on a soil test report in the Northeast.

Soil Acidity or pHSoil acidity or pH is the negative logarithm ofthe hydrogen ion concentration on a scale fromo to 14, with 7 being neutral (concentration ofhydrogen ions equals hydroxide ions). Table 1shows a diagram of nutrient deficiencies andother turf problems that are likely to occur atvarying p~ levels. In general, soil acidity at ornear neutrality ensures maximum availability ofall essential nutrients in the soil. This pH rangefavors the nutrients being in a plant-availableform. This is one of the simplest and mostimportant principles to remember about soilfertility and plant nutrition.

Lime RequirementLime requirement is the quantity oflimestone(CaC03) required to raise the pH of an acid soilto a desired level. A buffer solution is added tothe soil to determine buffer pH. The value itselfis not significant to the turf manager, but it is

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Table 2Essential nutrient elements, their function, and potential for deficiency or toxicity in plants.

Plant. Frequency of Toxicity orEssential Chemical Available Primary Mobility Deficiency in Deficiency ExcessiveMacronutrient Symbol Form Role in Plant Turfgrasses Occurrence OccurrenceCarbon COI Many Sometimes Drought stressHydrogen HIO Many Sometimes Drought stressOxygen 0 COI/OI Many Sometimes Compaction; waterlogged conditionsNitrogen NO- Constituent of amino acids, Mobile Common Sandy soils; high leaching; clipping removal; Salt toxicity; excessive growth;

NH;+ amides, proteins, nucleic acids, denitrification; low pH «4.8) succulencenucleotides, coenzymes, ete.

Phosphorus H{O~ Component of sugar phosphates, Mobile Sometimes Sandy, low C[C, irrigated soils; low pH «5.5); Excessive P may induce FeH 0,- nucleic acids, nucleotides, high pH (>7.5-8.5); high clay content soils; deficiency under some conditions

coenzymes, phospholipids, etc.; subsoils; high P demand during establishment;key role in reactions involving ATP reduced uptake in cold soils; clipping removal

Potassium K+ Required as a cofactor for many Mobile Sometimes High rainfall or leaching; sandy or low CEC soils; Salinity stress; suppresses Mg,enzymes; stomatal movements; acidic soils (pH<5.5); clipping removal; sites Ca, or Mn uptake; fertilizerburnmaintains electroneutrality receiving high Ca, Mg, or Na additions; underin plant cells high N fertilization; soils high in vermiculite,

illite,or smectite at high pHCalcium Ca Ca+1 Constituent of middle lamella of Immobile Rare low pH «5.5) conditions on low CEC soils Excessive Ca can induce Mg,

cell walls; required as a cofactor receiving high Na levels or with high AI, Mn, K, Mn, or Fe deficienciesby some enzymes or H; high leaching; true deficiencies are most

probable in root rather than shoot tissuesMagnesium Mg Mfl Constituent of chlorophyll Mobile Sometimes low pH «5.5); sandy soils due to low CEC Excessive Mg can induce

molecule and high AI, Mn, H; under high Na, Ca, or K deficiencies of K, Mn, and Caaddition; high leaching

Sulfur SO/ Component of some proteins Somewhat Sometimes low OM; sandy, low CEC soils; high rainfall and Foliar burn; induces extrememobile leaching; low atmosphere additions; high N with acidity in soils not buffered by

clipping removal free lime; contributes to blacklayer under anaerobic conditions

Iron Fe Fe+1 Constituent of cytochromes and Immobile Common High pH (>7.5); poor rooting; excessive thatch; High foliar Fe can blacken leaves,Fe+l nonheme iron proteins involved in cold and wet soils; high soil P at high pH; high possibly causing tissue injury; canFe-chelates pho~osy~thesis, NI fixation, and pH calcareous soils in arid regions; irrigation induce Mn deficiency; acidic, poorlyrespiration water with high HCOl, Ca, Mn, ln, P, or Cu; low drained soils can produce toxic

OM soils, heavy metals from sewage sludge levels of soluble Fe for roots

Manganese Mn Mn+1 Required for activity of enzymes Immobile Sometimes High pH, calcareous soils; peats and muck soils Toxicity to roots in acidic soilsMn-chelate and photosynthetic evolution of 01 that are at pH> 7.0; dry, warm weather; high (pH <4.8); anaerobic soils, high

levels of Cu, ln, Fe, Na, especially on leached, Mn levels can induce Ca, Fe, andlow CEC soils Mg deficiencies; Si and high

temperatures increase planttolerance to Mn toxicity

linc ln In+1 Constituent of enzymes Somewhat Rare Alkaline soils; high levels of Fe, Cu, Mn, P, or Some municipal wastes may belnOW mobile N; high soil moisture; cool, wet weather and high in In; high ln may causelow light intensity; highly weathered, acidic soils chlorosis by inducing Fe or Mgdeficiencies

Copper Cu Cu+1 Constituent of enzymes Somewhat Rare Strong binding of Cu on organic soils; heavily Toxic levels can occur from someCu(OHt mobile leached sands; high levels of Fe, Mn, ln, P, sewage sludge or pig/poultryCu-chelate and N; high pH manures

Molybdenum Mo MoO -I Constituent of nitrate reductase, Somewhat Rare Deficiencies are usually on acid, sandy soils; Mo toxicities are_ important forHMob, essential to NI fixation mobile acid soils high in Fe and AI oxides; high levels grazing animals and are associated

of Cu, Mn, Fe, S suppress uptake with high pH soils that are wetBoron

H~OlIndirect evidence for involvement Somewhat Rare High pH can induce deficiencies, especially on B toxicity is much more likely thanB -l in carbohydrate transport mobile leached, calcareous sandy soils; high Ca can deficiencies due to irrigation waterl restrict B availability; dry soils; high K may high in B; soils naturally high in B;

increase B deficiency on low B soils overapplication of B; use of somecompost amendments

Chlorine CI CI- Required for photosynthesis reactions Mobile Never CI uptake is suppressed by high NOl- and SO/" CI is a component of many saltsinvolved in 0

1 evolution that can be directly toxic to leaftissues and roots; more often itreduces water availability byenhancing total soil salinity

Nickel Ni Ni+1 Essential part of enzyme urease, Never Conditions associated with Ni deficiency are Ni toxicity can arise from use ofwhich catalyzes hydrolysis of urea not clear due to the rare occurrence of Ni some high Ni sewage sludgesto COI and NH, + deficiency

Adapted from Carrow et aI., 2001

4 GREEN SECTION RECORD

responses of all of the turfgrass species, overallSLAN has been the most tried and true nlethodfor estimating plant-available nutrients.

Remember, the numbers that you see on yourreport and the associated sufficiency levels arebased upon factors such as type of extractantused and the specific sufficiency index chosenfor interpretation. The articles by Carrow et al.(2003 and 2004) contain information aboutwhat are considered medium ranges for variousnutrients based on the extractant used. It ispossible that the recommended range providedin your report is so high that almost everysituation would indicate fertilizer need. It is allright if a lab uses a slightly different range aslong as it brackets the ranges provided in thearticles. Your decision, whether or not to applyfertilizer based on these results, should take intoaccount the likelihood for nutrient deficienciesto occur in your situation (see Table 2) as well asexisting turf grass health and performance.

Cation Exchange Capacityand Base Cation SaturationSoils have a net negative charge, whichattracts positively charged ions. Thus, cationexchange capacity (CEC) is a measure of theamount of cations that a soil can hold at a givenpH that are potentially exchangeable for plantuptake. CEC is often expressed on a weightbasis as milliequivalents (meq) per 100 grams ofdry soil or centimoles per kilogram (cmol/kg).A 100 g sample of soil with a CEC of 1 meq(considered very low) contains 6.02 X 1020

(602,000,000,000,000,000,000) negative chargesites. Without other information about a sample,knowledge of the CEC can provide someindication of the soil texture. Sands with loworganic matter by weight (1-2%) typically havevery low CEC values ranging from 1-3 cmol/kg, whereas most clay or clay loam soils are 20cmol/kg or greater.

The CEC is the sum total of basic or base (K+,Ca+2, Mg+2, and Na+2) and acidic (Al+3 and H+)cations. The amount of each listed in the report,divided by the CEC, is the saturation of that ion.It appears that a majority of turf agronomic con-sultants (excluding the USGA Green Sectionand university scientists) subscribe to the BasicCation Saturation Ratio (BCSR) theory forinterpretation of soil test results and fertilizerrecommendations. The theory is based uponhaving a base saturation of 80% comprised of

65% Ca, 10% Mg, and 5% K. Fertilizer recom-mendations are made to attain not only thesepercentages, but also desired balances betweenany combinations of the nutrients. Havinglistened to presentations by those who purportthis "feed the soil" theory, I am not surprisedthat a significant number of turf managers buyinto this theory, as it is an impressive display ofpseudoscience and salesmanship.

Unfortunately, the BCSR theory is largelyunfounded, and those who attempt to balancesoil cations on a routine basis are simply wastingtheir time and the club's money. To be morespecific, subscribing to the BCSR theory willlikely lead to the following: 1) Increased fertilizerrecommendations and usage that are not neces-sary relative to the SLAN method. 2) Raisingbase saturations in sand-organic matter soils tonear 80% can result in a significant increase insoil pH, which may lead to other problems suchas greater incidence of take-all or summer patchdiseases. 3) When relying on percentages ratherthan quantities of nutrients present in the soil, itis possible to have a sub-optimum percentage ofa basic cation such as K+ but sufficient levels ofextractable K+ or vice versa. 4) The theory oftenoverestimates soil Ca and underestimates soilCEC in greens or other areas containingcalcareous sands or after continuous irrigationwith Ca- and Mg-rich water. 5) It usually resultsin over-application of one base cation, which inturn depletes the availability of the others. Over-all, Ca and Mg deficiencies are rare in plantsexcept in unusual circumstances (Table 2).

Until recently, the BCSR theory has notbeen tested on turfgrass. However, researchconducted thus far further substantiates the lackof validity of the theory. When appropriateamounts of basic cations are applied, based onsufficiency data, the percent levels of cationsadjust naturally according to soil type. Does allof this mean that the CEC and base cationsaturation data should be ignored? Notnecessarily. This information can be useful formanaging salt-affected soils (i.e., high Na) and asa supplement to sufficiency levels to helpdetermine and evaluate fertility programs.

Soil NitrogenYour soil testing laboratory mayor may notreport tests of soil N because most forms of thisnutrient fluctuate too rapidly in the plant-soilsystem to be accurate and reliable predictors of

SEPTEMBER-OCTOBER 2007 5

available N. However, there is hope on thehorizon with utilization of the Illinois SoilNitrogen Test. The test, which predicts a morestable amino form of N, has been developed foruse in production agriculture and currently isbeing used to predict either N fertility needs forturfgrass, or identify turfgrass areas that haveincreased potential for nitrate leaching if Nfertilizer is applied. In the meantime, fertilizerrecommendations for N are based on turf re-sponse and are adjusted by the turf managerdepending on factors such as turf grass speciescomposition (e.g., Paa m111ua versus bentgrass),traffic, disease susceptibility, and environmentalstress conditions.

ROOTS ARE THE PRIMARYSITE OF NUTRIENT UPTAKEThese days I hear a lot about foliar nutrientapplications and products touted as being truly

Sometimes it can be difficult to differentiate between a nutrient deficiency and a diseaseor insect problem. Examine the turf thoroughly. In this case, damage from the annualbluegrass weevil caused yellowing of the turf.

foliar in function. While nutrients can be takenup by shoots, primarily through trans-cuticularpores, let's not forget that foliar uptake ofnutrients is minor compared to the effectivenessof the root system. When you think about it, theleaf is engineered to absorb light and preventwater loss. Factors that are likely to limit foliaruptake include cuticle thickness, rapid dryingbefore uptake, removal by mowing or precipita-

6 GREEN SECTION RECORD

tion, and volatility. Last but not least, truefoliar feeding requires a low volume of water«1 gallon per 1,000 ft2) for retention of spraydroplets in the foliage; conversely, most turfmanagers that I know use higher sprayer carriervolumes to distribute turf protectants deeperinto thatch or the underlying rootzone.

There is no doubt that light and frequentnutrient application is important in turfgrassnutrient management, especially on puttinggreens and other intensively managed areas.Call it semantics, but the term liquid fertilizationwould better describe the practice wherebynutrients are sprayed on the foliage, since uptakecan occur by both shoots and roots. The bottomline is, how much are you spending for your"true foliar" fertilizer?

NITROGEN UPTAKENitrogen is taken up by the plant primarily inthe forms of ammonium (NH4 +) and nitrate(N03-) ions and to a lesser extent as urea, whichare then assimilated into amino acids and otherimportant N compounds for growth andmetabolism. The question then becomes, is itbetter or more efficient for plants to circumventthis process and absorb amino acids directly?Although uptake of amino acids is possible, mysearch of the literature revealed only a scantreference to amino acid uptake by arctic sedge!Yet again I pose the question, how much are youspending for products containing amino acidsand other biostimulants? More research andproduct testing are needed to justify both thecost and efficiency of supplying nutrients to turfusing products like these.

GET THE MOST OUT OFLATE-SEASON FERTILIZATIONLate fall, or what some call "dormant" fertilizerapplications, are typical on cool-season turf innorthern, temperate climates. The ultimate goaloflate fall fertilization is to supply N to the plantfor carbohydrate storage, which can enhancestress tolerance and early spring root growth.Additional benefits include early spring greenupand reduced need for early spring fertilization,which can further enhance shoot growth andincrease mowing frequency. Since soil tempera-tures remain warmer than the air in the fall,roots are capable of taking up nutrients eventhough shoot growth has essentially ceased. Atthe same time, photosynthesis can still be active.

Thus, proper timing is achieved between thetime of the first hard freeze and continuoussnow cover or ground freezing when true plantdormancy occurs.

Slow-release forms ofN, including naturalorganics, are commonly applied in the late fallto avoid an unwanted flush of growth in theunlikely event that temperatures rise to abovenormal. Unfortunately, depending on the carrier,much of the N is not likely to be available to theplant until the following spring, which defeatsthe purpose of promoting root rather than shootgrowth. Furthermore, N may be lost in runoffor leached into groundwater.

It would be better to apply soluble, readilyavailable forms of N such as ammonium sulfateto ensure maximum root uptake and carbo-hydrate storage in late fall. If slow-release Nsources are to be used, then application shouldbe timed earlier in the fall, when warmertemperatures permit availability and root uptake.

Less than 1.0 pound ofN per 1,000 ft2 appliedwhen the turf is able to take up and utilize Nwill help to avoid potential losses due to leachingor runoff There is little evidence that late fallapplication of N contributes to low-temperatureinjury of cool-season turf grasses as long asproper rates and timing are followed. On theother hand, late fall N fertilization may enhancesnow mold activity on turf without a preventativefungicide application; however, the added N canalso help to hasten turf recovery from disease orother winter damage.

POTASSIUM FERTILIZATION:MORE IS NOT ALWAYS BETTERIn addition to its role in important physiologicalprocesses, K also influences tolerance to drought,cold, high temperature, wear, and salinity stresses.We also associate the term "luxury consumption"with K, in that tissue levels adequate for stresstolerance may be above what is considered

Disease or over-application of fertilizer?The granules tell thestory.

SEPTEMBER-OCTOBER 2007 7

Liquid applicationcan be an effectiveturf fertilizationmethod, but beskeptical of claimsthat hype foliaruptake when rootuptake is morecommon.

sufficient for growth. Knowing this, it appearsthat some turf managers have adopted the "moreis better" approach and apply 2-3 or more timesmore K than N on an annual basis. With theexception of situations involving salt-affectedsoils and salt-tolerant species, research hasdemonstrated optimal turfgrass stress tolerancewhen soil K is maintained in the sufficient range.Remember that excessive K can contribute tosalinity stress; suppress Mg, Ca, or Mn uptake;and promote greater incidence of snow molddiseases.

SUMMARYSoil fertility and turfgrass nutrition can bedaunting subjects to many turf managers. I hopethis article has helped to clarify and simplify keyprinciples and practices, and has empoweredyou, the turf manager, to take charge of yourturfgrass nutrient program. It doesn't require alot of money or guessing to meet the nutritionalneeds of your turf Let science be your teacher.

REFERENCESCarrow, R. N. 1995. Soil testing for fertilizer recommen-dations. Golf Course Management. 63(11):61-68.

Carrow, R. N., D. V. Waddington, and P. E. Rieke. 2001.Turfgrass soil fertility and chemical problems: Assessmentand management. Wiley, Hoboken, N.J.Carrow, R. N., L. Stowell, W. Gelernter, S. Davis, R. R.Duncan, and J. Skorulski. 2003. Clarifying soil testing:I. Saturated paste and dilute extracts. Golf CourseManagement. 71(9):81-85.Carrow, R. N., L. Stowell, W. Gelernter, S. Davis, R. R.Duncan, and J. Skorulski. 2004. Clarifying soil testing:II. Choosing SLAN extractants for macnutrients. GolfCourse Management. 72(1):189-193.

Carrow, R. N., L. Stowell, W. Gelernter, S. Davis, R. R.Duncan, and J. Skorulski. 2004. Clarifying soil testing:III. SLAN sufficiency ranges and recommendations. GolfCourse Management. 72(1):194-197.Chapin, F. S. III, L. Moilanen, and K. Kielland. 1993.Preferential use of organic N for growth by a non-mycorrhizal arctic sedge. Nature. 361:150-153.Gardner, D., and B. Horgan. 2006. 2006 Turfgrass andEnvironmental Research Summary. p. 15.

Happ, K. A. 1994. Tissue testing: Questions and answers.USGA Green Section Record. 32(4):9-11.

Happ, K. A. 1995. Sampling for results: The methods areimportant. USGA Green Section Record. 33(5):1-4.Kopittke, P. M., and N. W. Menzies. 2007. A review ofthe use of the base cation saturation ratio and the "ideal"soil. SSSAJ.71(2):259-265.Kussow, W. R. 2000. Soil cation balance. The GrassRoots. 29(2):58-61.Marschner, H. 1995. Mineral nutrition in higher plants.Academic Press, New York, N.Y.

Skorulski,J. E. 2001. Unlocking the mysteries: Interpretinga soil nutrient test for sand-based greens. USGA GreenSection Record. 39(1):9-11.

Skorulski, J. E. 2003. Digging deeper into soil nutrienttesting. Tee to Green. 33(1):3-5.

Skorulski, J. E. 2003. Micro-managing. USGA GreenSection Record. 41(5):13-17.

St. John, R., and N. Christians. 2007. Basic cation ratiosfor sand-based greens. USGA Turfgrass and EnvironmentalResearch Online. 6(10):1-9.

Taiz, L., and E. Zeiger. 1991. Plant physiology. Benjamin/Cummings. Redwood City, Calif

Woods, M. S. 2006. Nonacid cation bioavailability in sandrootzones. Ph.D. dissertation. Cornell University, Ithaca,N.Y.

THANKS TO Drs. Robert N. Carrow, University ifGeorgia; Paul E. Rieke, Michigan State University;andJames A. Murphy, Rutgers University;for theirassistance.

JIM BAIRD is a Green Section agronomist in theNortheast Region, where he visits golf coursesinConnecticut, New Jersey, New York, and Ontario,Canada.

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