Irrigation Water Quality Standards and Salinity Management

1 Irrigation Water Quality Standards and Salinity ManagementDr. Juan EncisoBiological and Agricultural Engineering DepartmentTexas A&M UniversityEffect of Water evaporation on concentration of salts==1 L of Water1 g of Salt1 % Solution2 % Solution1/2 evaporatedType of Salinity problemsSalinityhazardSodiumPlantsSoilsS aline soil conditionsSodic soil conditionsEC Electrical conductivity mmhos/cm mhos/cmdS/mTDS Total dissolved solids mg/lppm Total salinitySAR Sodium Adsorption ratio ---Terms used in salinitySodium hazardESP Exchangeable sodium %

2 --- Water Quality in selected wellsin Far West TexasLocation EC SAR mhos/cmSt. Lawrence 4500-5800 6-7 Pecos 2330-2680 8-12 Coyonosa 2100-3810 4El Paso AD 800 900 limits for the Irrigation waterClasses of Water EC mhos/cm TDSppmExcellent 250 175 Good 250-750 175-525 Permissible 750-2000 525-1400 Doubtful 2000-3000 1400-2100 Unsuitable 3000 2100

3 Sodium hazard of the waterSAR values Sodium hazard Comments 1-10 Low Sensitive crops10-18 Medium Amendments and leaching 18-26 High Unsuitable-continuous>26 Very high UnsuitableClassification salt affected soils0413EC (mmhos/cm)SARN ormalSalineSaline-SodicSodic0 Salinity controlLeachingApply more Water than the crop consume to push the salts below the root zone at at some time during the yearHigh Water TableDrain - ditches, pipeDrain pipe manufacturingSocks for drain pipeExtraction tubesLining canalsReduce seepage30 in deep1 ft-w bottom$100,000 mileSodicity controlSubstitute Calcium for SodiumAnd then leach the SodiumGypsumCalcium Nitrate Sulfur to solve calciumFar West Texas(Region E)

4 Common constituents of Irrigation waterCations Amonium NH4 Calcium CaHidrogen HMagnesium MgSodium NaPotasium KAnionsBicarbonate HCO3 Carbonate CO3 Nitrate NO3 Phosphate PO4 Sulfate SO4 Water TestingRoutine analysis $20 Conductivity, pH, Na, Ca, Mg, K, CO3, HCO3, SO4, Cl, B, Nitrate, Hardness and SARR+ Metals $30Zn, Fe, Cu Mn, and PR+ Metals+ Heavy Metals $50As, Ba, Cd, Pb, Cr, and FlourideSoil TestingRoutine analysis $10pH, NO3, P, K, Ca, Mg, Na, S, and ConductivityR+ Detailed Salinity $25R+ Micro-nutrients $20Z, Fe, Cu, MnTotal Dissolved solidsExcellent Poor LimitHumans 0-800 2,500-4,000 5,000 Cattle 0-1,000 4,000-6,000 10.

5 000 ToxicityBoronChlorideSodiumSalt ToleranceForage corpsField cropsVegetablesFruitsMoreLessIrrigation Water Salinity tolerances-ForagesCrop 100% 90% 75% 50%Tall wheat grass grass grass Barely hay More YieldLess SalinityLess YieldMore SalinityCrop 100% 90% 75% 50%Bermuda grass forage Cantaloupe Soil Salinity tolerancesSalt accumulationVery high high moderate low ECw 4 ECw 8 ECw 16 Single row bedDouble row bedSeeds fail to germinateSalt accumulationSalt build-up as a function of seed placement5000 acres of SDI per year in District 6 Furrow - 35 lbs/ac-inSDI - 55 lbs/ac-inExcellent - 65 lbs/ac-in40 80 Drip spacing8 12 20 cm30 cmDrip depthOverlapping is important- UniformityFoliar injury.

6 Cotton (resistant) Alfalfa (medium)Center pivot more than 400 GPMCost per 1/4 mile New $40,000$320/acnot included supply line and pump electricitySurface Irrigation - Need to level the landSize of the bordersPercent slopesoil textureBorder irrigationE