Managing salts in soil and irrigation water - GCSAA

GCM - January 2001 - Research - Managing salts in soil and irrigation waterwhen gypsum is added to the soil, thegypsum may revert to insoluble lime(CaCO 3 ) in the presence of excessHCO 3- and CO3 = (3). Hence, in orderto use sulfur to form gypsum, it is necessarytoremove excessive HCO 3- andCO 3=. Superintendents should be verycareful when they use sulfur burners,because, under anaerobic conditions,reduced forms of sulfur may lead toblack-layer problems later on. Therefore,sulfur products should be used inareas that are well aerated and have noinfiltration problems.Another reason superintendents useacid-injection systems is to reduce soilpH. Unfortunately soil pH cannot bechanged easily by such acid applications,because soil has a huge bufferingcapacity. Reducing soil pH is very difficultor even impossible in highlybuffered, calcareous soils (3). It is muchmore practical and also less expensive toreduce soil pH by spreading sulfur overdry soil as an amendment.A few superintendents use acid injectionin order to prevent the precipitationof calcium and magnesium carbonatesin irrigation plumbing, but thisproblem can be solved with muchcheaper materials. A weak organic acidand a weak organic base combinationwill take care of the problem, and thesetypes of materials are readily availableand relatively inexpensive.on threshold EC values, but final selectionshould be made after checking thegrowth vs. EC level, threshold EC valuesfor 50 percent growth reduction ofshoot and root. Seashore paspalum hashigh salinity tolerance, can toleratewaterlogging and has a low soil-oxygenrequirement (4). These attributes makeseashore paspalum an ideal turfgrasscultivar for warm-climate golf coursesfacing severe salinity problems.LeachingLeaching of excess salts is the mostimportant step in managing salts.Without leaching, the replaced sodiumand the excess salts beyond the rootzone plague turf. It is difficult to leachpush-up greens or other parts of thegolf course that have finer soil texture.Leaching is more of an art, which asuperintendent learns through experienceand knowledge about the soil texture,the amount of water required orthe time needed for a particular green.If we try to understand the movementof water through a soil profile, wewill find that, according to the laws ofhydraulic conductivity, a particular soilhorizon will release water as soon as itreaches field capacity. Water movesAtomic weightsR E S E A R C HSelection of turfgrassProper turfgrass selection is animportant management tool when salinityproblems are anticipated. Differentcultivars have differential responses tosalinity levels. For example, commoncentipedegrass (Eremochloa ophiuroides)is sensitive to salt levels, whereasseashore paspalum (Paspalum vaginatum)can tolerate higher salinity levels(14 decisiemens per meter) (1). Salt-sensitiveplants (glycophytes) should bereplaced with halophytes. When selectinga turfgrass species, it is advisable tocheck the growth versus EC curves forthat particular species. Turfgrass selectionfor salinity tolerance is often basedFor some calculations of water quality, units must be expressed as millequivalentsper liter. Generally, labs report values in parts per million or milligramsper liter. Such values need to be divided by the equivalent weight toobtain millequivalents per liter.Ions Atomic/molecular Equivalentweight (grams) Valence weight (meq/liter)Ca ++ 40 2 20Mg ++ 24 2 12Na + 23 1 23HCO 3- 61 1 61CO 3=60 2 30Golf Course Management ■ January 2001 73