Fairbanks Ranch Country Club (Rancho Santa Fe, California) successfully demonstrates that, with carefulmaintenance practices, a quality golf course can be achieved despite having been built on a salt lake bed.

Understanding Water Qualityand Guidelines to ManagementAn overview of challenges for water usage on golf courses for the 21st century.

by R. R. DUNCAN, R. N. CARRO~ and M. HUCK

WTH GLOBAL demand for freshor potable water doubling every20 years, competition for this

valuable resource will increase in the21st century. Potable water reservescomprise only 2.5% of the total avail-able global water supply, with ground-water reserves averaging about 1.7% ofthat total. For groundwater, only 45 %is fresh water, and this source supplies30% ofthe human and industrial users,with the remainder from surface waterresources. This potable water dilemmawill result in turfgrass managers havingno choice but to irrigate with recycledand other non-potable alternative

14 USGA GREEN SECfION RECORD

water resources of lesser quality thatcontain increased levels of dissolvedsalts.

Several overriding issues will change21st-century turfgrass managementstrategies. A primary concern is waterquality and the consistency of thatwater quality. Non-potable water canbe referred to as brackish, effluent, re-cycled, wastewater, reclaimed, regen-erate, or grey water. Water releasedfrom sewage plants can vary fromprimary to secondary to tertiary treat-ment levels, and quality will be partiallydictated by the 1) quality of the originalsource prior to potable use, 2) salts

and solids added by first-time users(e.g., discharges from factories or by-products of other manufacturing facili-ties), and 3) contamination of salts andsolids added via surface runoff intotreatment facilities.

Quality factors include the presenceof:

1. Solids (sand-silt-clay and organicparticles) that potentially can clog theirrigation delivery system, plug soilmicropores, and cause excess wear onsprinkler nozzles and pumping com-ponents.

2. Biological (nematodes, weed seeds,algae, fungal spores) and chemical

Continuous use of saline water sources without leaching the soils canlead to serious salt accumulations and ultimately tur/grass decline.

ppm

meq/L

ppmandmeq VI

Often, the laboratory analysis comesback with confusing units for some ofthe data values. The conversion factorscan be found in Table 1.

analytical laboratory for analysis. Whatdata should you ask for, and in whatspecific units should these data bepresented? PreferredQuality Factor _U_n_it_s__Water pHCarbonates and mg/L,Bicarbonates ppm, or

meq VITotal Salinity (impact on plantgrowth from higher total salts)

Electrical dS/mconductivity (EC)Total dissolvedsalts (TDS)

Ion Toxicity (impact on rootand foliar contact)

Na meq/L and ppmCI ppmB ppm

Na Permeability Hazard(impact on soil structure)

Sodium meq/Ladsorptionratio (SAR)Adjusted SAR(adj SAR)Residual sodium meq/Lcarbonate

Nutrients

involving grass selection, cultivation,and irrigation scheduling must bedeveloped accordingly.

High sodium concentrations, espe-cially in conjunction with high bicar-bonates and relatively low calcium(Ca+2) and magnesium (Mg+2) levelsidentified in the water analysis, canpotentially cause a sodium perme-ability hazard. This hazard must beassessed, and high values have thepotential for developing serious soilstructural deterioration and water in-filtration problems. Assessment andmanagement strategies must be 1)based on site-specific soil and waterconditions and 2) aggressively moni-tored and frequently adjusted toaddress specific constraints involvinggrass selection, amendments to thewater and/or the soil, regular cultiva-tion, and careful irrigation scheduling(leaching) .

Specific toxic ions must be assessedas to their level of toxicity and theirpotential impact on the turf root sys-tem as well as foliar damage. Finally,nutrient load in the irrigation water isa fourth problem that can contribute asubstantial amount of fertilizer to theturfgrass and can often induce defi-ciencies of other critical nutrients insalt-challenged turf grass systems.

Calculations and Unit ConversionsDevelopment of an effective manage-

ment program starts with collection ofa representative water sample and sub-mission of that sample to a reputable

(pesticides, fertilizers, other salt resi-dues, pollutants) materials that canaffect turfgrass performance.

3. Salt-related problems such as totalsalinity, sodium permeability hazard(impact on soil structure), specific toxicions, and nutrient balance.

Water quality variability is site-specific and can change seasonally or,in extreme cases, on a daily basis. Thefocus of this article is on assessment ofwater for these salt-related problems.

Water Quality AssessmentWater quality assessment is one of

the most confusing and complex prob-lems facing turf managers. The typesand quantities of chemicals that areapplied to the turf system through irri-gation water have a dramatic influenceon soil chemical/physical aspects andturf performance. Variable levels ofsalts and extreme environmental con-ditions (high prolonged heat andhumidity, severe drought, and traffic)magnify water quality problems. Watersamples submitted to laboratories foranalysis often come back with data inconfusing units or with no referencepoints. Do you have a problem with thewater on your course? How do youassess the data? What are the criticalpoints to look for? How can you adjustyour management to prevent a poten-tial future problem? These are all validquestions that will be addressed in thisarticle.

ProblemsFour critical problem categories

must be considered from the data pre-sented in a water analysis report: totalsalt content, sodium permeabilityhazard, specific ion toxicity, andcritical nutrient levels. Each categoryis a salt problem but differs from theother three problem areas in specificeffects on soil traits and turf perfor-mance. In addition to these salt prob-lems, inorganic or organic suspendedsolids need to be consistent. The fourproblem areas can result in many dif-ferent combinations and degrees ofstress.

High total salts or total salinityconcentrations will often reflect thepotential for a saline soil problem todevelop. Saline conditions inhibitwater uptake by turfgrasses and causea salt-induced drought stress. This is themost common salt-related water issuethat occurs and must be managed ongolf courses. Total salinity problems aresite-specific and must be assessed onthat basis, and management strategies

SEPfEMBER/OcrOBER2000 15

Other Conversion Factors:1 mmhos cm-i = 1 dSm-1 = 1,000 umhos cm-i = 0.1 Sm-i

. 1 umhos cm-i = 0.001 dSm-i = 0.001 mmhos cm-i

1 ppm = 1 mg VI (solution) = 1 mg kg.i (soil)1% concentration = 10,000 ppm1 mmole Vi = 1 meq Vi1 ECw (dSm-i) = 640 ppm (TDS = Total Dissolved Salts)TDS (ppm) = ECw x 640; TDS (lb./ac.-ft.)::= TDS (ppm x 2.72)ppm = grains per gallon+ x 17.2(grains/gallon is still used by domestic effluent water purveyors to report hardness)Sum of cations and anions (meq Vi) ::=EC (dSm-i) x 10

Note: 1 mg VI = 1 ppmFor example, to convert 220 mg VI Na+ to meq VI:

(220 mg VI) x (0.043) = 9.46 meq VI Na+

Electrical Conductivity of Water

a yellowish brown and purplish color,depending on turf species. Salt crystalsmay actually form on the soil surface,especially in bare-soil areas. Salts thatcontribute to total salinity include cal-cium, potassium, magnesium, sodium,chloride, sulfate, nitrate, ammonium,and bicarbonate.

Electrical conductivity (ECw) is theextent to which water conducts elec-tricity, which is directly proportional tothe concentration of dissolved salts.ECw is used to estimate the total dis-solved salts (TDS) in water (TDS 7640 = ECw). TDS will occasionally bereferred to as total soluble salts (TSS)or total dissolved solids (TDS) byanalytical laboratories. Irrigation watercontaining high total salts such assewage effluent can lead to saline soilconditions and poor turf grass perfor-mance. Most sewage effluent rangesfrom 200 to 3,000 ppm TDS or ECw =0.30 - 4.7 dSm-i (Feigin et al., 1991).

Irrigation quantity, leaching durationand frequency, drainage requirements,and turf species/cultivar selection re-quirements increase as ECw or TDSincreases (Table 2). Water quality moni-toring must be used to predict futuresoil salinity problems and to adjustmanagement strategies to minimizedeterioration of turfgrass performance.

Management Strategiesfor Total Salinity

Indicators of total salinity impact onturfgrass growth will be ECw and TDS,and both measurements are interre-lated. When a water analysis indicatesthat total soluble salts (> 0.75d Sm-iECw or > 500 ppm TDS) are the pri-mary problem, irrigation schedulingand cultivation plus leaching becomethe predominate management options.Sodium (Na), chlorine (CI), and boron(B) levels may be high, and if ECw >1.50 dSm-i and TDS > 1,000 ppm, selec-tion of salt-tolerant turf species andspecific cultivars within that speciesbecomes increasingly important.

Drainage requirements also increasesince leaching frequency and the waterquantity needed for leaching escalatesas the total salinity hazard increases.Leaching directly affects nutrient avail-ability, particularly with mobile ionssuch as potassium (K), magnesium(Mg+2), nitrate (N03t iron (Fe), andmanganese (Mn). Fertilizer programsmust be adjusted accordingly, and thistopic will be discussed in the sectionon "Nutrient Variability."

The success or failure of the manage-ment strategy for dealing with high total

Multiply by:

0.011001006.4640640

0.0016

To convert meq/L toppm, multiply by:

23.020.012.235.439.048.030.061.0

In USGA greens, the perched watertable zone, located below the normalrootzone, is an area of potential saltaccumulation where salts could rise bycapillary action into the rootzone dur-ing high ET periods. To avoid capillaryrise, sufficient surface water must beapplied to break tension in a USGA-type green and periodically flush outexcess salts. In a native soil, a netdownward movement of salts beyondthe active turf rooting area must bemaintained by ample irrigation.

Excess salts inhibit water uptake byturfgrass roots and cause wilting. Saltsliterally prevent water uptake even ina moist soil, and the turf can changecolor rapidly (sometimes overnight) to

ConvertECwmSm-1 to dSm-i

dSm-1 to mSm-1

mScm-i to m,Sm-i

mSm-itoppmdSm-i to ppm

mScm-i to ppmppm to dSm-i

Table 1. Conversion factors

To convert ppm tomeq/L, multiply by:

0.0430.0500.0830.0290.0260.0210.0330.016

K+IS04-2

C03-2

HC03-

SodiumCalciumMagnesiumChloridePotassiumSulfateCarbonateBicarbonate

Total SalinityThe most common salt problem on

turf is accumulation of high total saltsleading to a saline soil condition.Saline soils can cause salt~induced orphysiological drought. Turfgrass symp-toms include reduced growth, dis-coloration, wilting, leaf curling, andeventually leaf firing. or desiccation.Drought or water stress symptoms canoccur a) if salt from irrigation water isallowed tp accumulate within the root-zone, b) if accumulated salts in therootzone (previously added by salt-laden irrigation water) rise up into theactive rootzone by capillary action, orc) when both occur simultaneouslyduring hot, dry periods.

16 USGA GREEN SECfION RECORD

Salinity ECw IDSHazard Class (dSm-1) (ppm)

Low <0.75 <500

Medium 0.75 - 1.50 500 - 1,000

High 1.5 - 3.00 1,000 - 2,000

> 2,000 .>3.00

Table 2. Total salinity hazard classification guidelines for variablequality irrigation water based on ECw and TDS (Carrow and Duncan, 1998)

ManagementRequirements

No detrimental effectsexpected

.Moderate leachingto prevent saltaccumulationTurf species/ cultivarselection, goodirrigation, leaching,drainageMost salt-tolerantcultivars, excellentdrainage, frequentleaching, intensivemanagement

Very HighExcess suspended solids can plug water-conducting pores at the soil surface.Low-quality effluent irrigation sourcesare notorious for containing high loadsof suspended organic solids.

salts is predicated on one key aspect ofturf management, namely water man-agement. In particular, good irrigationscheduling and adequate volumes thatpromote leaching are essential. Cultiva-tion is an integral part of regular man-agement in salt-affected environments,encompassing both deep aeration (8-12 inches) once or twice each yearand shallow aeration (3-6 inches) asneeded, depending on soil texture.Infiltration, percolation, and drainagewill dictate how effectively total saltsare moved away from the turfgrass rootsystem and are not allowed to buildup in subsoil layers where they couldpotentially rise to the rootzone duringperiods of inadequate leaching.

Theoretically, sandy soil profiles areeasier to leach than heavier clay soils.However, both soil types often requireregularly scheduled deep and shallowcultivation followed by adequate leach-ing to move the excess salts downward.If aeration is regularly performed, butirrigation is scheduled for only 5-10minutes daily (Le., light, frequent irriga-tion), salts can move back up throughthe soil micropores by capillary action,form a concentrated layer in the root-zone, and limit water uptake or evenkill the turf root system. This usuallyoccurs when evapotranspiration (ET)exceeds the amount of water appliedto the turf during prolonged hightemperature or windy conditions. Also,if large diameter aeration holes are notbackfilled with topdressing sand priorto leaching, large volumes of water canrun into the holes and beyond the sur-face, while leaving behind a salt-ladenzone between holes.

High salt levels from even low vol-ume total salt applications (TDS = 600-800 ppm) can build up in subsoil layersover time in sand-based greens duringprolonged dry periods. These salt layersusually can be found at depthscorresponding to how deep theirrigation water percolated into thesand profile. If only a low volume «0.50 inch) of irrigation water is applied,the salt accumulation zone is oftenlocated just below the root system atabout 6-8 inches depth, unless totalsalts are leached deeper by a periodicheavy flushing from rainfall or irriga-tion. Any zone of salt accumulation onsandy soils should be at least 12-16inches deep, and on fine-textured soils,at least 16-24 inches deep to limit apossible rapid capillary rise of saltswhen irrigation volume is not sufficientfor net leaching.

At shallower depths, salts can risewithin two or three days through capil-lary action and evapotranspirationduring extreme hot and prolonged dry,windy conditions. The salts may havebeen added through irrigation water at600-800 ppm levels (which is normallynot a problem), but the subsurface saltaccumulation zone will be at muchhigher concentrations that can quicklydesiccate and kill the turfgrass rootsystem. Thus, net downward watermovement is essential to avoid saltlayers near the turfgrass rootzone. Aheavy nighttime leaching program fol-lowed by an afternoon hand-wateringof localized dry areas on sand-basedgreens may be necessary to preventturfgrass collapse when temperaturesexceed 90-95°P for one to two weeks or

more. The rule of thumb to minimizesalt accumulation is to increase watervolume applied by 12.5% for each 640ppm rise in total dissolved salts (TDS)in the irrigation water.

Additionally, high total salts canhave a growth regulator effect on turf-grasses because water uptake is limited.Regardless of the level of salt tolerance,all turfgrass cultivars will experiencesome growth reduction from high saltaccumulations. The most salt-tolerantcultivars (for example, seashore pas-palum cultivars Sea Isle 1, Sea Isle2000) have high inherent growth ratesso that they maintain adequate growthfor recovery from injury and for long-term performance when under persis-tent salt stress. Less salt-tolerant culti-vars can be significantly affected whenother stresses such as low mowingheight « 'l4 inch), high salt-indexsoluble fertilizers, shade, and excessivetraffic/wear/compaction negativelyaffect long-term turf performance. Sitescontinually irrigated with salt-ladenirrigation water should restrict carttraffic on the golf course to cart pathsonly, especially on turf species andcultivars with low salt tolerance.

Sodium Permeability HazardThe sodium concentration in con-

junction with the quantity and type ofother salts in irrigation water have amajor influence on a) water infiltrationinto and percolation through soil pro-files by directly affecting soil perme-ability, b) the leaching fraction, or thequantity of water required to leachexcessive Na or other salts, c) whetherthe water should be treated prior to

SEPTEMBER/OCTOBER 2000 17

Table 3. Sodium permeability hazard and specific toxic ion reference points(Adapted from Harivandi and Beard, 1998; Carrow and Duncan, 1998)

Sodic and Saline-SodicSoil Formation

The relative quantities of soil Ca,Mg, and Na are extremely important.Calcium is the primary ion that stabi-lizes soil structure. Magnesium offerssecondary structural stability. Whenexcess Na (> 200 ppm) is appliedthrough irrigation water, the Na con-tent builds up over time and eventuallywill displace the Ca+Z ions that are thebuilding blocks and that enhance thestructural integrity of the clay fractionin the soil profile. This "push-and-shove" relationship, which is domi-nated by a larger Na+ion with a weakerforce or charge for holding clay par-ticles together, eventually results in soilstructure breakdown. The result is asodic soil. It is sometimes referred to asblack alkali, since the excess sodiumprecipitates out the organic matterfraction in the soil, which in turn risesto the soil surface. The deposit on thesurface is black with a slick, oilyappearance. Where excess Na+ andhigh total salts are both present, it iscalled a saline-sodic soil and is charac-terized by having both white salt de-posits and black decomposed organicmatter deposits on the surface.

Very few turfgrasses can survivethese sodium hazard conditions sincethe soil structural breakdown results ina sealed soil with little or no waterpermeability. Classic symptoms on golfcourses are heavily compacted areas,areas with long-standing puddles, anddead turf. A secondary symptom can besurface algae and black layer formationcaused by the constant moist condi-tions and the lack of oxygen in the turfroot system. Sodium adsorption ratios(SAR or adj SAR) exceeding 6 meq L-lindicate that the Na+ levels are highenough to cause structural deteriora-tion in some soils.

A more subtle symptom often occursin sand-based greens or on fairwaysand tees where clay soil profiles havebeen capped with sand. On greens,short duration (5-10 minute) daily irri-gation scheduling when using high Nairrigation water may eventually result ina layer forming in the sand profile. Thislayer normally will be as deep as thewater percolates downward each day(usually somewhere between 4 and 12inches deep). While sands often con-tain few clay colloids, Na+ can causeorganic matter of colloidal size tomigrate to this depth and start to sealthe soil pores, eventually leading toblack layer formation. High sulfur or

High> 18>9> 16>24> 18>9

> 2.50

RSC = (C03 + HC03) - (Ca + Mg),in meq L-l

Table 4. Calculation for adjustedsodium adsorption ratio andresidual sodium carbonate

RSC or residual sodium carbonate

adj SAR or adjustedsodium adsorption ratioa) adj SARw = SAR [1 + 8.4 - pHc]

(refer to Carrow and Duncan 1998,and Ayers and Westcot 1985)

b) adj SARw is also calculated bythe Hanson et al. (1999) method

late adj SARw and residual sodiumcarbonate (RSC) according to Table 4.

Specific ToxicIonsSodium Content Low Moderate High

--Toxicity to roots SARw <3 3-9 >9

ppm < 70 70 - 210 > 210Toxicity to leaves meq L-l <3 >3

ppm < 70 > 70Chloride Content

Toxicity to roots meq L-l <2 2 - 10 > 10ppm < 70 70 - 355 >355

Toxicity to leaves meq L-l <3 >3ppm < 100 > 100

Residual Chlorine (Clz) ppm <1 1-5 >5Boron toxicity on roots ppm < 0.7 0.7 - 3.0 >3.0Bicarbonate content meq L-1 < 1.5 1.5 - 8.5 >8.5

ppm <90 90 - 500 >500*2:1 claysare shrink-swell clays

**1:1 claysdo not shrink (crack) on drying or swellon wettingOther 1:1 types are Fe/AIoxidesand allophanes

Clay type unknownMontmorillonite (2:1)*Illite (2:1)*Kaolinite (1:1)**Sands with ECw > 1.5 dSm-1

Sands with ECw < 1.5 dSm-1

RSC (residual sodium carbonate)

Irrigation Water Components Degree of ProblemSodium permeability hazard (Na+-induced soil structural deterioration,and low water/oxygen permeability)SARw or adj SARw (sodium adsorption ratio) by clay type (ppm)

Low Moderate< 10 10 - 18<6 6-9< 8 8 - 16< 16 16 - 24< 10 10 - 18<6 6-9

< 1.25 1.25 - 2.50

application to enhance infiltration/percolation into the soil, and d) theoptions available to adjust manage-ment scenarios to maintain or enhanceturf performance. Two key water com-ponent relationships must be deter-mined before management decisionscan be made: Sodium adsorption ratioand bicarbonate/carbonate levels.

The SARZlJ, or sodium adsorptionratio, is used to assess the sodiumstatus and permeability hazard (Table3). Sodium, calcium (Ca), and mag-nesium concentrations (in meq L-l) areused to compute SARw:

SARw= Na~ (Ca + Mg)/2

When bicarbonate (HC03-) andcarbonate (C03-Z) concentrations are> 120 and 15 ppm, respectively, calcu-

18 USGA GREEN SECTION RECORD

sulfate concentrations in the water willenhance the process.

The salts and excess Na congregatein this zone and, with normal evapora-tion, the salt concentration will gradu-ally increase. When evapotranspirationexceeds irrigation, coupled with pro-longed hot, dry, and/or windy condi-tions, these concentrated salts willmove back up into the turf rootzone,cause salt-induced drought, root dessi-cation, and may even kill the turf. Theturfgrass will turn purple or yellow toyellowish-brown to brown, usuallywithin 24 hours, depending on the turfspecies.

A similar scenario can develop onfairways, roughs, or tees where sand (4-10 inches in most cases) is used to capa heavy clay soil. The high Na irrigationwater will usually result in a concen-tration of excess Na ions at the interfaceof the sand cap and clay. Unless theexcess Na+ moves laterally under thesand cap (drainage lines can help), itwill eventually break down the claystructure and the subsoil will seal off.Symptoms during wet periods will becontinuously damp, boggy areas withpossible standing water. In dry periods,salts may rise into the rootzone.

The type of clay soil has a profoundinfluence on the amount of Na that willeventually cause soil structural deterio-ration. Soils that crack open when theydry (montmorillonite, illite) tolerate amuch lower Na concentration beforesoil structural deterioration, mainlybecause Na+easily enters between clayplatelets, and because of the increasedexposure of the clay particle exchangesites to excess Na as these soils expandand contract. Soils that have non-swelling clays (kaolinite, Fe/Al oxides)tolerate much higher Na concentra-tions before structural breakdown be-cause the Na ion has more difficulty

.migrating into these non-expandingsoils and in-between clay platelets.

Regardless of clay type, once a soilhas deteriorated into a sodic condition,-turning this condition around will re-quire a program of aeration, applicationof Ca+2source amendments, high-vol-ume leaching, and careful turfgrassselection. Calcium amendments shouldbe applied immediately following aera-tion to avoid acceleration of permea-bility problems in the soil profile at thedepth of the aeration treatments. Thisscenario is the most complex and diffi-cult salt stress to overcome and maytake several months to several years toaccomplish. With poor quality, salt-laden water as the only irrigation

source, management at a high level willhave to be constant to prevent the sodicsoil condition from reoccurring.

Bicarbonate andCarbonate Influence

Another set of water data factorsis also important in influencing Na+activity - namely, relative levels ofbicarbonates (HC03-) and carbonates(C03-2) in relation to Ca+2and Mg+2concentrations (Tables 3 and 4). Whenhigh HC03- and C03-2 levels (> 120and 15 ppm, respectively) are appliedthrough the irrigation water, these ions

Acid injection and sulfur burnerscan be used to treat water with excessbicarbonate levels. Acidifying irrigationwater to a pH of 6.5 reducesbicarbonates by approximately 50%.

react with Ca+2and Mg+2to form in-soluble CaC03 and MgC03• The de-creased levels of Ca+2and Mg+2from thisreaction process reduce the amount ofthese ions that can compete with Na+for exchange sites on the clay particles.As the Na+ content increases throughdaily irrigation applications, the Na+dominates these exchange sites andcauses soil structural breakdown. Thesoil becomes sealed, water does notpercolate into the soil profiles, andthe turf eventually dies. The insolubleCa/Mg carbonate forms precipitate outinto the soil, and remaining bicarbon-ates reduce the effectiveness of gypsumor sulfur treatments to the soil.

The sodium permeability hazard inirrigation water is usually assessed bySARwvalues when HC03- is < 120 ppmand CO/ is < 15ppm. The SARw valueincorporates the influence ofNa+, Ca+2,and Mg+2concentrations. Above theselevels, adj SAR is preferred since thesevalues incorporate the influence ofHC03- and C03-2.

Residual sodium carbonates (RSC)also are used to assess the sodiumpermeability hazard, and this valueincludes the influence of HC03- andC03-2 as compared to Ca+2 and Mg+2(Tables 3 and 4). As a general rule,whenever HC03- exceeds 120 ppm, it isa good idea to calculate RSC. It is notthe absolute levels of HCOJ- andCO/ present in the irrigation waterthat are important, but the relativeconcentrations of HC03- and COJ-2

compared to Ca+2, Mg+2, and Na+levels.

When HC03- and C03-2 concentra-tions exceed soluble Ca and Mg con-centrations, water acidification may beneeded if residual sodium carbonateand adjusted sodium adsorption ratios(adj SARw) exceed 1.25 and 6 meq VI,respectively (Table 3). If HC03- andC03-2 concentrations are < 120 ppm,RSC < zero, and adj SARw < 6 meqVI, then acidification of irrigation watershould not be needed. Know all threevalues before deciding to purchase asulfur generator or acid injection sys-tem for water treatment! (Carrow etaI., 1999)

If the RSC is > 0, indicating residualcarbonates remain above those re-moved by Ca and Mg precipitation,another option is to add gypsum ora soluble Ca+2source to prevent Na+accumulation in the soil. One meq VICa must be added for each meq VIHC03• However, any previously pre-cipitated Ca and Mg tied up by theexcess bicarbonates (positive RSCvalue) will not be active or available.Thus, acidification will remove thebicarbonate and will make availablethe Ca and Mg contained in or addedto the irrigation water to react with theexcess Na adsorbed to soil CEC sites.Additional Ca could be supplied byadding gypsum or a soluble Ca source.The amendments are intended to im-prove soil water infiltration and perco-lation. (Refer to Carrow et aI., 1999,Green Section Record, 37(6):11-15 formore information on water treatmentoptions to improve infiltration.)

SARlECw InteractionThe interaction of SARw and ECw

on soil water infiltration is presented inTable 5. High total (salt) electrolyteconcentrations in the irrigation watercan counteract the adverse effects ofNa on causing soil deterioration. Whenirrigation water is very low in salts(ECw < 0.5 dSm-I), permeability prob-lems can arise at the soil surface evenat low SARw (1-10 meq VI). All irriga-

SEPTEMBER/OCTOBER 2000 19

*Soil permeability = ability of water to infiltrate into the soil and percolate/drain.Gas exchange is reduced by low soil permeability.

Table 5. Interaction of sodium adsorption ratio (SARw) andelectrical conductivity (ECw) on soil water infiltration

(Harivandi and Beard, 1998)

Salt-Laden Irrigation Water (dSm-1)

Influence on Soil Permeability*

SARwand No Slight to SevereECw Restriction Moderate Restriction Restriction

SARw= 0-3 0-3 0-3ECw= > 0.7 0.7 - 0.2 < 0.2

SARw= 3-6 3-6 3-6ECw= >1.2 1.2 - 0.3 < 0.3

SARw= 6 -12 6 -12 6 -12ECw= > 1.9 1.9-0.5 <0.5

SARw= 12 - 20 12 - 20 12 - 20ECw= > 2.9 2.9 - 1.3 < 1.3

SARw= 20 - 40 20 - 40 20 - 40ECw= > 5.0 5 -2.9 <2.9

tion water should contain at least 20ppm or 1 meq L-1 Ca and have a mini-mum ECw = 0.5 dSm-1 to prevent soildispersion (Petrie 1997). At high ECw(> 3 dSm-1), the high electrolyte (salt)concentration can function in main-taining soil permeability even with ahigh SARw (15-30 meq L-l). Thus, ahigh Na hazard in the soil can bereduced by irrigation water with a highECw (see Table 3).

(Refer to Duncan and Carrow, 1999,Golf Course Management, May: 58-62, or Carrow and Duncan, 1998, forthe gypsum requirements to reduce soilexchangeable sodium percentage.)

Specific Ion ToxicityIrrigation water may contain toxic

levels of certain ions that affect turf-grass in 1) root tissues due to soilaccumulation, 2) shoot tissues due touptake by the turf roots and accumu-lation in leaves, and 3) directly on thefoliage of landscape plants due tosprinkler irrigation. The ions thatcause toxicity problems include Na,CI, B, HC03, and pH (H+or OH- ions).As total salinity increases in irrigationwater, the potential for specific iontoxicity also increases. Germinatingseed, young seedlings, and sprigs areespecially vulnerable because of theirjuvenile root systems. '

The specific ion toxicity guidelines(Table 2) apply to sensitive turf andlandscape plants, but soil accumulation

20 USGA GREEN SECTION RECORD

of these ions can eventually causedamage to even tolerant turfgrass. Overtime, sodium can become toxic to turfroots, since it accumulates in the soiland leaves of susceptible turf genotypesat SAR > 3 meq L-l or 70 ppm. Chloride(CI) can accumulate at potentially toxiclevels for roots and leaves at 2-3 meqL-l or 70-100 ppm, and can restrict Nuptake. Excess CI normally accumu-lates in the tips of leaves. In turf,regular mowing plus collection anddisposal of clippings removes thesehigh concentrations from the turf andsoil system. But leaf removal is nor-mally not a management option forlandscape plants, or may be limitedon turf under non-mowed conditions,such as in naturalized roughs.

Residual chlorine (CI2) that is used todisinfect wastewater becomes toxic at> 5 ppm. HC03 concentrations are nottoxic at > 8.0 meq L-l or 500 ppm, butcan cause unsightly deposits on leavesand equipment and can contributeto excess Na+ deterioration of soilstructure.

Depending on the source, some irri-gation effluent can contain high levelsof heavy metals and other ions (Carrowand Duncan, 1998). Maximum concen-trations of selected heavy metals Zn(2.0 ppm) and Cu (0.2 ppm) are note-worthy since these ions can restrictuptake of iron (Fe) (Table 4). Themaximum concentrations for Fe (5.0ppm) and Mn (0.2 ppm) are important

to know since these elements tend tobe deficient in salt -affected and highlyleached turfgrass systems. These maxi-mum guidelines are based on thepotential to achieve toxic levels overtime with long-term use of the water.

Soil and Water pHWater pH and soil pH are additional

management considerations. The keyreference points are pHs < 5.0 (H+dominates on the acidic level) and> 8.5(OH- dominates on the alkaline level).When pHs are at or beyond thesespecific extremes, management levelsmust be increased accordingly to mini-mize deterioration in turf performance(Carrow and Duncan, 1998).

The effect of water pH on alteringsoil pH is often short term because thebuffering capacity (CEC) of most clayand loam native soils is so high thatmany years of irrigation will be requiredbefore, a significant change will occur.Soils with lower CECs (sands, decom-posed granites, crushed lava rock)should be monitored closely for pHchanges. Accordingly, acidifying waterfor the sake of pH modification isquestionable when cost analyses areconsidered. However, when high bi-carbonates are supplied in combinationwith excess Na in the water source(which ties up the Ca/Mg needed tocounter the Na), water acidificationwould be justified. Additionally, whenthe water pH is in the 8.0-8.5 range, useof acidifying fertilizers (sulfur-basedsources) to dissolve some of the freecalcium carbonate (lime) can countersome of this alkaline soil pH reaction.

Be aware that extreme water pH andhigh salt concentrations, when used inthe sprayer mix with fungicides, herbi-cides, or insecticides, can have aneffect on efficacy. This is particularlytrue with organophosphate and carba-mate chemistries. Consult with manu-facturers regarding each particularproduct when confronted with thisproblem.

Critical Nutrient ConsiderationsAll irrigation water will contain a

certain level of nutrients in its compo-sition, and wastewater may containelevated levels of certain nutrients.Due to the nutrient load in effluentirrigation water, fertility programs mustbe adjusted to maximize turfgrass per-formance and to minimize environ-mental impact (King et a1., 2000).

Nutrient guidelines in irrigation arecompared in Tables 5, 6, and 7. Keyratios to calculate include Ca:Mg,

*Irrigation water with nutrient concentrations outside these ranges can be used;the fertility program must be adjusted to avoid deficienCies.

Table 7. Reclaimed water guidelines - recommended maximum values(Adapted from L. J, Stowell, 1999. Pointers on reclaimed watercontract negotiations. Fairbanks Ranch meeting. June 7,1999.)

Table 8. Nutrient ratios in irrigation water and potential deficiencies *Ca:Mg < 3:1 Ca deficiency

> 8:1 Mg deficiency

Ca:K < 10:1 Ca deficiency> 30:1 K deficiency

Mg:K < 2:1 Mg deficiency> 10:1 K deficiency

Table 6. Nutrient guidelines in irrigation water (ppm)

Nutrient Low Normal High Very High

P <0.01 0.1- 0.4 0.4 - 0.8 > 0.8P04" < 0.3 0.3 - 1.21 1.21 - 2.42 > 2.42P20S <0.23 0.23 - 0.92 0.92 - 1.83 > 1.83

K <5 5 -20 20 - 30 >30K20 <6 6 - 24 24 - 36 >36Ca <20 20 - 60 60 - 80 >80Mg < 10 10 - 25 25 - 35 >35N < 1.1 1.1 - 11.3 11.3 - 22.6 >22.6

N03- <5 5 - 50 50 - 100 > 100S < 10 10 - 30 30 - 60 >60

S04- <30 30 - 90 90 - 180 > 180

CI (ppm) 250Na (ppm) 200Fe 5.0Mn 0.2Zn 2.0Cu 0.2Ni 0.2

tion water in small amounts provide alight topdressing to the native soil.

The primary concern with suspendedsolids is their effect on newly con-structed sand greens that can poten-tially be contaminated by these fine-particle-size solids delivered duringseed germination, establishment, andgrow-in. If significant amounts ofsuspended soil fines are applied at thisstage, soil surface micro pores can be-come plugged, function like a layer of

TDS (ppm) 960

ECw (dSm-I) 1.5SARw 5.7adj SARw 11.6RSC (meq VI) < 1.25HC03 (ppm) 250B (ppm) < •• 0.5

mature wear or plugging of sprinklerand pumping components as well asincreasing the potential for pluggingmicropores, which conduct soil surfacewater.

Suspended solids generally havelittle or no impact on native soils (fair-ways, roughs, landscaped areas) orpushup soil tees and greens, becausethe added solids normally are similarin particle size to the native soil. In thiscase, solids added through the irriga-

Ca:K, and Mg:K (Table 8), especially insalt-affected sites that are irrigated withsalt-laden water. When dealing withthese conditions, certain managementconsiderations should be considered.

• Because of the high mobility of K+and the propensity of Na+ to displaceK+on soil exchange sites, a regular K+application may be needed every 2-4weeks to maintain a nutritional balancein the turf plant.

• Due to high leaching events withsalt-laden irrigation water, Fe and Mnmay be needed on a regular basis inspoon-feeding format.

• Highly soluble nitrate sources[Ca(N03)2] are recommended in aspoon-feeding approach to maximizeturf uptake and utilization in a salt-challenged environment.

• Less soluble, slow-release productswith lower salt indexes may be moreappropriate when planning soil-appliedfertilization programs to reduce thetotal salt load in the turf rootzone.

• Avoid unnecessary sulfur applica-tions (except when in conjunction withlime to form gypsum) because theycan lead to black layer and anaerobicproblems in turf.

• If P, P04-, and P20S concentrationsare in the normal range, do not applyadditional P-based fertilizers since thisnutrient is one of the least mobile ofnutrients in the soil and can contributeto algal blooms in holding ponds orcontamination in surface and subsur-face water resources.

• Avoid foliar calcium applicationssince this element is the least mobile ofnutrients and is an element that is moreeffectively taken up by roots thanthrough foliar tissue.

Total Suspended SolidsSuspended solids are inorganic or

organic materials (sand, silt, clay,plant debris, algae) that do not dis-solve in water and can only beremoved by filtration. While total sus-pended solids (TSS) is normally notconsidered a salt problem, it is animportant water quality characteristic.Low quality effluents are notorious forcontaining high volumes of organicsolids. The overall effect on hydraulicconductivity is governed by particlesize and quantity of suspended in-organic and organic solids. Organicmaterials include humic substancessuch as fulvic acid 'and humic acidthat exhibit both soil aggregating andanti-aggregating properties. Excesssuspended solids, and particularly sandcontamination, often contribute to pre-

SEPTEMBER/OCTOBER 2000 21

foreign soil or incompatible topdress-ing, and inhibit water infiltration andpercolation. If the irrigation water issalt-laden, the fines can settle at thebottom of the wetting zone and de-velop a layer where excess saltsaccumulate and concentrate. If ET ishigher than the volume of irrigationthat is applied, the concentrated saltscan rise through capillary action intothe turf rootzone to cause salt injury.

Unfortunately, no specific guidelineshave been published for predicting thelevel at which TSS becomes a hazard.Interpret TSS data based on commonsense and the potential impact thatcontaminants mayor may not have onsoil structure and irrigation systemcomponents. Use the following methodto evaluate the TSS hazard:

1)The water quality test reports TSSin parts per million (ppm) or milligramsper liter (mg VI).

2) Multiply the value by a conversionfactor of 2.72. The resulting value isequivalent to the pounds of solids peracre-foot (325,852 gallons), or thevolume of solids applied to each acrewith 12 inches of irrigation water.

For example:1) Water quality test reports 22 ppm

TSS.2) 22 ppm x 2.72 = 59.84 or 60 lbs.

of solids applied per acre-foot of waterapplied to the turf.

3) Is this a problem? Not likely, sincethis amount (60 lbs./acre-foot) is equiv-alent to one bag of cement spread overthe golf course with each acre-foot ofwater applied. Sand, silt, and clayparticle residue from a windy daywould provide more solids than thiswater source (Kopec, 1998).

4) If the TSS was 735: 735 ppm x2.72 = -2,000 lbs. or 1 ton of solids peracre-foot. This volume of fines couldbe a problem on sand greens. Filteringthe water or providing settling pondswould be options to consider.

SummarySteps in assessing water quality

to determine turfgrass managementoptions:

1. Check for bicarbonates and car-bonates in the water. If concentrationsare greater than 120 ppm and 15 ppm,

respectively, calculate adj SARw andRSC to verify the degree of impact thatthese ions will have on Ca and Mgactivity. Adj SARs > 6 meq VI and RSCs> 1.25 may indicate that acid treatmentplus lime or gypsum applications areneeded.

2. Check Na content and calculateSARw or adj SARw and RSC to assessimpact on soil structural deterioration(Na permeability hazard). Also, evalu-ate ECw in conjunction with SAR oradj SAR to estimate the permeabilityhazard (Tables 3 and 5). Knowledge ofthe clay type will be useful. Thesevalues will determine the level of aerifi-cation, amendments, and leaching thatwill be needed.

3. Check ECw and TDS for theirimpact on turfgrass (Table 2). High totalsalinity values in conjunction with lowNa+ and HC03- values would indicatethe potential to create a saline soil con-dition and will determine the degree ofaeration and leaching needed as yourprimary management options.

4. Check S and/or sulfate levels inthe water. If S > 60 ppm or S04 > 180ppm, you may need to use lime as an

This patch of seashore paspalum is surviving better than the surroundingbermudagrass in this poorly drained, high-saLt-content soil.

22 USGA GREEN SECTION RECORD

Without proper management, sodium, in combination with bicarbonates, can causecrusting and sealing of the soil surface.

amendment. The high sulfates (sulfur)in the water will combine with lime toform gypsum. Removing the excesssulfur and sulfates will help minimizeanaerobic problems and black layerformation when regular aeration andleaching are used in managementprotocols.

5. Check actual Na, CI, and B valuesfor their specific ion toxicity potential(Table 3). These ions normally willaffect landscape plants and susceptibleturf cultivars, but continued accumu-lation can eventually influence eventolerant species. Plants tolerant to hightotal salinity also are generally tolerantto high levels of these specific ions.

6. Check levels of actual nutrientsand make appropriate adjustments inyour fertility program to account fornutrient additions or any induced defi-ciencies (Tables 6 and 7). CalculateCa:Mg, Ca:K, and Mg:K ratios andadjust the fertility program accordingly'(Table 8). Watch for deficient levels ofFe and Mn. With very high CI- levels,you may need to increase N by 10-25%.P and K are critical to maintenance ofa good root system in a salt-challengedecosystem. Annual P and K rates mayneed to be increased 25-50'% above non-salt-affected sites, but with a spoon-feeding application regime. High Caand Mg applications to replace excessNa can depress K uptake. High Naalso depresses K uptake. N:KzO ratiosshould be maintained at 1:1 up to 1:1.5by light, frequent applications.

7.Aerate, aerate, aerate followed byleach, leach, and leach. Keep the saltsmoving!

Glossary of Term~Acid injection: Used to treat water withhigh HC03 and C03 content. Adding anacid evolves the HC03 and C03 off as CO2and water. Commonly used sources includesulfuric, urea-sulfuric, and S02 gas fromsulfurous generators.B: Boron, a micronutrient, essential at verylow concentrations. Can become toxic atsoil concentrations of 0.5-6.0 ppm. Mostturfgrasses have a good tolerance to boron,while some ornamental species are verysensitive.Bicarbonate: HC03 ion.Ca: Calcium is an essential plant nutrientand cation responsible for good soilstructure.CaCI2: Calcium chloride, a very solublecalcium salt that can be dissolved in irriga-tion water to lower the SAR or increase theECw.CaC03: Calcium carbonate (lime), insolubleform of calcium precipitated by water highin Ca, HC03, and C03• Sometimes naturally

occurring in calcareous/caliche soils inarid regions. Insoluble until reacted with anacid.CaC03• MgC03: Calcium/magnesium car-bonate (dolomitic lime), insoluble calcium/magnesium combination precipitated fromwater high in Ca, Mg, HC03, and C03•

Sometimes naturally occurring in calcare-ous/caliche soils in arid regions. Insolubleuntil reacted with an acid.Carbonate: C03-2 ion.CaN03: Calcium nitrate, a highly solublesource of calcium and nitrogen that can bedissolved in irrigation water to lower theSAR or increase the ECw.CaS04: Calcium sulfate, commonly referredto as gypsum. An amendment used to dis-place sodium from the soil exchange sitesand can be added to irrigation water(usually as a suspension) to increase ECwor the ratio of Ca/Na, thereby loweringSAR.CEC: Cation exchange capacity, the sumtotal of exchangeable cations that a soil canabsorb.CI: Chloride is required in small amounts asa plant nutrient; it is a highly soluble saltand toxic in larger quantities (70-100 ppm).Trees and ornamental plants are often moresensitive to chloride than turf, and accumu-lation is first noted in leaf tips. Most plantsare generally more sensitive to chloride saltsthan sulfate salts.C12: Chlorine, used by water treatmentplants to disinfect water of various patho-gens. Excess or residual chlorine (> 5.0ppm) can cause toxicity.C03: Carbonate, combines with Ca (cal-cium) and Mg (magnesium) to form CaC03

and MgC03 (calcium carbonate and mag-nesium carbonate) forms of insoluble limeor calcite.

Cu: Copper, an essential micronutrient, butif concentrations are excessive (> 0.2 ppm)can restrict the uptake of iron.dS/m_1: Decisiemens per meter, the stan-dard measurement used to report electricalconductivity of water (ECw).ECw: Electrical conductivity of irrigationwater. This is a measure of the total salinityor total dissolved salts. 640 ppm TDS = 1.0dS/mECw.ESP: Exchangeable sodium percentage,used to classify sodic and saline-sodic soilconditions. The degree of saturation of thesoil exchange complex with sodium ascompared to other exchangeable cationsoccurring from irrigation with sodium-dominated water.ET:Evapotranspiration, the total amount ofwater loss from soil evaporation and planttranspiration.Fe: Iron, essential plant nutrient that tendsto become depleted in highly leached, salt-affected soils.H:zS04: Sulfuric acid, either forms in soilwhen acidifying amendments/fertilizers areused such as soil sulfur (S), ammoniumsulfate, etc., or is injected into irrigationwater via a sulfurous generator or acidinjection and products such as urea sulfuricacid (NpHURIC).HC03: Bicarbonate, combines with Ca(calcium) and Mg (magnesium) to formCaC03 and MgC03 (calcium carbonate andmagnesium carbonate) forms of insolublelime or calcite. Can also cause unsightlydeposits on omamentals.K: Potassium, an essential nutrient thatinfluences rooting, drought, heat, cold, anddisease tolerance. Potassium can be dis-placed by sodium at the cation exchangesite.

SEPTEMBER/OCTOBER 2000 23

1.25 - 2.5>2.5

DR. RON R. DUNCAN (tur/grass genetics/breeding, stress physiology) and DR.ROBERT N. CARROW (tur/grass stressphysiology and soil physical and chemicalstresses) are research scientists in theCrop and Soil Science Department, Uni-versity of Georgia, Georgia ExperimentalStation at Griffin. MIKE HUCK is anagronomist with the USGA Green SectionSouthwest Region.

Harivandi, A. 1998. Reclaimed water irri-gation. GCSAA, Lawrence, KS. 129p.Harivandi, M. Ali. 1999. Interpreting turf-grass irrigation water test results. Univ.California Pub. 8009 (http://anrcatalog.uc-davis.edu).Harivandi, M. A., and J. B. Beard. 1998.How to interpret a water test report. GolfCourse Mgmt. 66(6):49-55.Hayes, Allan. 1995. Comparing well waterwith effluent: what superintendents need toknow. Golf Course Mgmt. June: 49-53.Hawes, Kay. 1997. Quenching golf's thirst.Golf Course Mgmt. June: 71-72, 74, 78, 80,84-86.King, K.W, J. C. Balogh, and R. 0. Harmel.2000. Feeding turf with wastewater. GolfCourse Mgmt. January: 59-62.Kopec, 0. 1998. True grit - understandingTSS on a water quality report. Cactus Clip-pings. Newsletter of the Cactus. and Pine(Arizona) Golf Course SuperintendentsAssociation.

.Newcom, J., and E. McCathy. 1999. Lay-person's guide to water recycling. WaterEducation Foundation. Sacramento, CA95814.Pitrie, S. E. 1997.Understanding irrigationwater quality. UNOCAL Solution Sheet.April: 1-4.R)lOades, J. D., A. Kandiah, and A. M.~ashali. 1992. The use of saline waters for

./ crop production. FAO Irrigation and Drain-age Paper #48. Rome, Italy. 133p.Ross, B. B. 1988. Irrigating turf grass underadverse water quality conditions. Land-scape and Irrigation 12(4): 148, 150, 151,154..Schinderle, Gary. 1990. Identifying andcorrecting severe water quality problems.Golf Course Mgmt. May.Throssell, C. S., and 0. M. Kopec. 1994.Irrigation water quality. Salt-affected irri-gation water and soil: impact on turf-grass growth and management. GCSAA,Lawrence, KS. 50p.U.S. Golf Association. 1994. Wastewaterreuse for golf course irrigation. Lewis Publ.,Chelsea, MI.Yenny, Reed. 1994. Salinity management.USGA Green Section Record 32(6):7-10.Zupancic, J. 1999. Reclaimed water: chal-lenges of irrigation use. Grounds Mainte-nance 34(3):33,36,38,85.

ReferencesAyers, R. S., and 0.W Westcot.1985. Waterquality for agriculture. FAO Irrigation andDrainage Paper, 29. Rev. 1, Food and Agric.Organiz., Rome, Italy.Berndt, W Lee. 1995. "Quality'" waterfor your plants. Landscape Management34(10): 21-23.Bond, W. J. 1998. Effluent irrigation- anenvironmental challenge for soil science.Austral. J. Soil Res. 36: 543-555.Borchardt, Julie. 1999. Reclaiming a re-source. Golf Course Mgmt. Jan.: 268-272,276-278.Carrow, R. N. 1995. Water quality testing forturfgrass sites. Ga. Turfgrass Assoc. Mgmt.Brief #1. 7p.Carrow, R. N., and R. R. Duncan. 1998.Salt-affected turfgrass sites: assessment andmanagement. Ann Arbor Press, Chelsea,MI. 185p.Carrow, R. N., R. R. Duncan, andM. Huck.1999. Treating the cause, not the symptoms.Irrigation water treatment for better infil-tration. USGA Green Section Record.37(6): 11-15.Cohen, Stuart, A. Surjeck, T. Durborow,and N. L. Barnes. 1999. Water qualityimpacts by golf courses. J. Environ. Qual.28: 798-809.Duncan, R. R., and R. N. Carrow. 1999.Establishment and grow-in of paspalumgolf course turf. Golf Course Mgmt. May:58-62.Duncan, R. R., and R. N. Carrow. 2000.Seashore paspalum, the environmentalturfgrass. Ann Arbor Press, Chelsea, MI.Feigin, A., L. Ravina, and J. Shalhevet. 1991.Irrigation with treated sewage effluent.Management for environmental protection.Springer-Verlag. Berlin.Hanson, Blaipe, Stephen R. Grattan, andAllan Fulton. 1999. Agricultural Salinityand Drainage. Div. Agric. Natural Res. Pub.3375, U. Cal. Irrig.. Program, Univ. Calif.,Davis, Ca. 160p.

S03 Generator: Sulfurous generator, alsoknown as a sulfur burner. Equipment usedto treat irrigation water containing highcarbonates and bicarbonates. Bums sulfurat high temperatures to produce sulfurousgas that when combined with water be-comes sulfuric acid. This evolves the HC03and C03 off as CO2 and water. This isanother method of acid injection.S04: Sulfate, when combined with limewhile in an acid form creates gypsum. Mayalso combine with other cations to formvarious soluble salts.IDS: Total dissolved salts, normally re-ported as parts per million (ppm).TSS: Total suspended solids, organic andinorganic materials (sand, silt, clay, algae,plant debris, etc.) that do not dissolve inwater and must be removed by filtration orsettling.

Potential Irrigation UseGenerally safe forirrigationMarginalUsually unsuitableunless treated

S: Sulfur, a secondary plant nutrient used asa soil amendment to modify pH in alkalinesoils. Also used in calcareous and calichesoils (containing high lime) to convert limeinto gypsum.SARw: Sodium adsorption ratio of irriga-tion water. SARw is used to determinewhether sodium (Na) levels of water willcause soil structure to deteriorate. Unad-justed SAR (SARw) considers only Na, Ca,and Mg.Adj SAR: Adjusted sodium adsorptionratio of irrigation water. Adj SARw predictsthe increased influence of sodium (Na)upon soil structure due to the influence ofcarbonates and bicarbonates.

meq/l: Milliequivalents per liter. Parts permillion (ppm) divided by equivalent weightequals milliequivalents per liter.mg VI: Milligrams per liter, equals parts permillion.Mg: Magnesium, an essential plant nutrientand cation associated with good soil struc-ture, providing it is not available in exces-sive quantities in relationship to Ca.MgC03: Magnesium carbonate, insolubleform of magnesium precipitated by waterhigh in Mg, HC03, and C03. Sometimesnaturally occurring in calcareous/calichesoils in arid regions. Insoluble until reactedwith an acid.Mn: Manganese, essential plant nutrientthat tends to become depleted in highlyleached, salt-affected soils.Na: Sodium, non-essential as a nutrient, a"small" cation with a large hydrated sizethat disperses soils, thereby affecting infil-tration and soil aeration. Can displacepotassium on soil exchange sites.N~S04: Sodium sulfate, a soluble saltformed when gypsum is used to treat soilswith high sodium content.pH (water): A logarithmic measurement ofrelative alkalinity or acidity. Water withlow pH often reflects higher quantities ofsulfates or iron, while high pH tends toreflect high bicarbonates or sodium.ppm: Parts per million. Milliequivalents perliter multiplied by equivalent weight = partsper million.RSC: Residual sodium carbonate, like theadj SARw, it is used to determine whetherNa will cause soil structure problems. TheRSC compares the concentrations of Caand Mg to HC03 and C03 and determineswhen calcium and magnesium precipitationcan occur in the soil and result in additionalsodium domination of soil cation exchangesites. RSC = (C03 + HC03) - (Ca + Mg).This calculation is done with all measure-ments in meq/l.

RSCValue< 1.25

24 USGA GREEN SECTION RECORD