Salt Injury -- an Increasing Problem - USGA Green Section Record

Salt Injury-An Increasing Problemby DONALD D. HOOSWestern Director, USGA Green SectionSalt inhibits bermudagrass establishment on poor land site.tWIt"-ottsrrA-*-:

APROBLEM OF increasing occurrencein Southern California andother areas of the Southwest isestablishing and maintaining turfgrassesin areas of poor soil quality. This isparticularly true of establishing grassesin areas of high salt accumulation. Moreand more golf courses are being builton sites unsuitable for any other purpose.Soil conditions on these sites areusually less than ideal. On the aridsolstypically found in the Southwest, manysites used for golf courses are high inclay content with a great deal of calciumcarbonate or gypsum present in theform of caliche. The soil pH is usuallybetween 7.0 and 8.0 on these soils. Ifwater used for irrigation is high insodium, its combination with the aridsolscan be a problem.Problems occur when sodium cannotbe leached below the root zone of thegrass plant. Poor drainage in these claysoils is often a problem on poor landsites used for golf course construction.Because of the high salt content of bothirrigation water and the soil, sodiumhas a tendency to accumulate at the soilsurface. Evaporation rates in the Southwesttend to be high, and this furtheraccentuates salt accumulation at thesoil surface.The use of effluent water for irrigationalso adds to the problem of salt accumulation.Because of evaporation duringthe holding process as water movesfrom domestic use to the effluent processingplants, sodium levels becomemore concentrated. Effluent watergenerally has slightly higher sodiumlevels than subsurface water used forirrigation. The combined use of poorland sites and effluent water for irrigationof new golf course developmentsshould be carefully screened for identificationof salt-related problems.High salt levels affect turfgrassvisually by causing wilting and a bluegreenappearance, followed by irregularstunting of growth. Tip burn is oftenpresent. An anaerobic layer is oftenformed in the upper root zone andthatch layer. This layer is typically blackin color and exudes a readily identifiableodor. Under these conditions, lessoxygen enters the root zone to promoteaero bic microbial activity. Growth ofroots in this layer is quite difficult, evenfor bermudagrass.brings us to the major method in solvingestablishment and management problemsunder sodium conditions - drainageand leaching. If drainage can beimproved to allow sufficient movementof water through the root zone and toleach accumulated salts, there is a betterchance to avoid salt problems. If watercan penetrate and move through the soilprofile, there is less evaporation nearthe soil surface and thus less accumulationof sodium in the root zone.Therefore, one of the first stepstoward correcting a sodium problemshould be to seek ways of improvingdrainage in any affected areas. Installationof French drains may be sufficient;other areas may need recontouring toallow surface drainage away from lowspots. In some cases, redesign of theirrigation system may be needed. Relocationof sprinkler heads may also beneeded to solve a sodium problem inlow areas in front of greens. The overlapof green and fairway sprinkler heads inlow areas in front of greens often resultsin accumulation of excess sodium.Often, by moving heads or reprogrammingof the irrigation sequence, thisproblem can be overcome withoutadditional measures.AerationSalt injury on bermudagrass has appearance of being diseased.Another important process in establishingand maintaining grasses in highsodium areas is to aerate and cultivateaffected areas regularly. The coringprocess relieves compaction andimproves water penetration. It alsoencourages oxygen exchange in the rootzone and helps prevent anaero bicconditions from developing.AmendmentsMost of the soils in the Southwest aretypically high in calcium. For thisreason, many of the soils exhibitingsodium problems do not respond togypsum applications. In some cases,gypsum will modify the effects ofirrigation water high in sodium and theturfgrass will benefit. This is especiallytrue on sand and in putting greens.Acidifying the soil with sulfur or sulfurcontainingmaterials will produce themost dramatic results in solving sodiumproblems. The sulfur tends to improvethe soil's infiltration rate by dissolvingcalcium carbonates which accumulateon the soil particles and act as pluggingagents. Lowering the soil pH as a resultof regular sulfur applications also tendsDrainageUnder high salt conditions, poorquality turfgrass develops in low spotsand in poorly drained areas wheresodium concentration is greatest. This2 USGA GREEN SECTION RECORD

New salt-tolerant grasses are being developed.to make needed soil nutrients, such asiron and phosphorus, more available tothe turfgrass plant.Grass VarietyChoosing the right grass variety for useunder high salt conditions is anotherimportant consideration. There is nodou bt that certain grasses tolerate muchhigher levels of salt than others. A greatdeal of research is being directed towarddeveloping grasses that tolerate higherlevels of salt than grasses presentlyavailable. In the past few years, severalnew grasses have been released thathave a high tolerance for sodium. Fultsalkaligrass was released by ColoradoState University several years ago.Under cool season grass conditions, itdoes remarkably well at higher saltlevels. Adelaide and Futurf, varieties ofPaspalum vaginatum, are warm seasongrasses that also tolerate relatively highlevels of sodium. Their appearance andgrowth habits are similar to commonbermudagrass. Research is being conductedat the University of California(Riverside) on these grass varieties todetermine the effects of commonmanagement practices on their growthand establishment.Of presently available grasses for useon golf courses, the bermudagrasseshave the best tolerance for sodium. Ofthe cool season grasses, creeping bentgrasseshave a higher salt tolerance thanperennial ryegrasses or Kentucky bluegrasses.All have a higher salt tol~rancethan Poa annua. Seaside creeping bentgrasshas a higher salt tolerance thanPenncross.RelativeSaltToleranceGoodMediumPoorTurfgrassBermudagrassZoysiagrassCreeping bentgrassTall fescuePerennial rye grassRed fescueKentucky bluegrassColonial bentgrassCentipedegrassSummaryThe turfgrass species, soil texture anddepth of the salt concentration in thesoil profile are all factors than can affectturfgrass growth under high salt concentrations.A high salt concentrationimpairs the absorption of water andessential plant nutrients. Impaired seedgermination and poor vegetative establishmentare often encountered whenhigh sodium conditions exist. Physicalproperties of the soil are also alteredwhen sodium levels are high. Sodiumcauses detlocculation of the soil colloids.This can lead to a reduction in soilaeration which increases susceptibilityto compaction and decreases waterinfiltration rates.The best solution to sodium pro blemsis to leach away the excess sodiumthrough improved drainage andincreased aeration of pro blem areas.Soil amendments to acidify the areamay be beneficial if leaching of excesssodium can also be achieved.NOVEMBER/DECEMBER 1981 3