Managing Water Quality in Growing Media David Wm. Reed Department of Horticultural Sciences Texas A&M University

Factors That Impact Water Quality in Growing Media

n Irrigation Water Quality

Factors That Impact Water Quality in Growing Media

Irrigation Water Quality n Chemical Properties u pH u alkalinity u EC u SAR n Individual Soluble Salts n Water Treatment Methods

Growing Medium EC and pH (from Lang 1996) SaturatedPaste1:2DilutionPourThrough pH All Plants EC dS/m Young Plants Established Plants

Irrigation Water Alkalinity Limits Minimum Maximum Minimum Maximum ppm meq/lppmmeq/l Plugs and/or seedlings Small pots/shallow flats " to 5" pots/deep flats ” pots/long term crops (from Bailey 1996)

Irrigation Water Critical Limits (from Biernbaum 1994) MinimumMaximum pH EC (dS/m) ppm Alkalinity40160 Ca2575 Mg1030 S040 Na020 Cl020 Fe01 Zn00.5 B00.1 Cu00.1 Mo00.1 F00.1

Plant Nutrient Requirements Supplied by Irrigation Water Nutrient Minimum ppm To Supply Plant Requirements S ppm Ca 40 ppm Mg 20 ppm B 0.3 ppm

Sulfur Supplied by Irrigation Water (from Reddy 1996) ppm supplies most plant’s requirement

Irrigation Water Quality n Water Treatment Methods

Water Purification Methods (from Reed 1996) ReverseOsmosisWaterSoftenerAcidInjectionAeration/OxidationActivatedCarbon/Al Alkalinity(carbonates) XX Total Salts X SodiumXX ChlorideXX IronXXX BoronX FluorideXX ManganeseXXX CopperXX CalciumXX SulfateX

Reverse Osmosis Unit

Reverse Osmosis Water Purification To Decrease Salts Pretreatments: 1) Polymer injectionto coagulate due to high SDI 2) Depth Filterto remove coagulated particles 3) Charcoal Filterto remove municipal chlorine 4) Ion Exchangeto remove residual polymer Purification System: Reverse Osmosisusing polyamide membranes (pH resistant, chlorine sensitive) (pH resistant, chlorine sensitive) Production Capacity Purified Water 5,760 gallons per day Blended Water (40/60)14,400 gallons per day Blend to EC of0.75 dS/m (approx. 500 ppm) (from Reed 1996)

Reverse Osmosis Water Purification To Decrease Salts Costs Lease and Service$900 per month Water (1.09/1,000)$700 per month Electricity$200 per month Total$1800 per month Purified Water Cost1 cent per gallon Blended Water Costs0.4 cents per gallon Production Space Irrigated 80,000 to 135,000 square foot of 6-inch production space (at oz/6”pot/day at 0.9 sq. ft. space/6”pot) Purified Water Used For Salt sensitive foliage plants and mist propagation (from Reed 1996)

Acid Injection 80% Neutralization to Approx. pH 5.8 Fluid ounce of acid ppm per 1,000 of water,per oz. per for each meq1,000 gal Acidof alkalinitywater Nitric (67%) N Phosphoric (75%) P Sulfuric (35%) S (from Bailey 1996)

Fertilizer Program n Soluble Liquid Feed n Granular Incorporation n Controlled Release Incorporation

Factors That Impact Water Quality in Growing Media

EC of Soluble Fertilizers & Water Quality (from Peterson 1996)

Fertility & Salt Stratification in the Root Zone Subirrigation – New Guinea Impatiens ‘Barbados’ (from Kent & Reed 1996)

Irrigation Method n Top-Watering vs. Subirrigation n Vertical Stratification of Salts n Evaporation from Surface n Leaching Fraction

Factors That Impact Water Quality in Growing Media

Vertical Stratification of Soluble Salts

Salt Stratification in the Root Zone with Different Irrigation Methods (from Molitor, 1990, Warncke & Krauskopf 1983)

Evaporation from Surface Causes Vertical Stratification of Salts

(from Argo and Biernbaum 1995 Warncke & Krauskopf 1983) Effect of Evaporation on Salt Stratification Poinsettia ‘Gutbier V-14 Glory’

Effect of Evaporation on Salt Stratification Poinsettia ‘Gutbier V-14 Glory’ (from Argo and Biernbaum 1995 Warncke & Krauskopf 1983)

Vertical Stratification of Soluble Salts and and Root Distribution

Salt Stratification & Root Distribution Spathiphyllum in subirrigation (from Kent & Reed, unpubl; Warncke & Krauskopf 1983)

Track EC to Monitor u Soluble Salt Accumulation u Over Fertilization u Minimum Fertility Level Caution: DO NOT sample the top layer

Graphical Tracking: EC Crop: ______________________

Leaching Fraction and and Soluble Salt Accumulation

Leaching in Top-Watering Vs. Subirrigation

Leaching Fraction in Top-Watering LF ~ Low LF High LF LF  EC w / (5(EC e(desired) -EC w ))

Effect of Leaching Fraction on Medium EC Poinsettia ‘V-14 Glory’ (from Yelanich and Biernbaum 1993, Warncke & Krauskopf 1983) 0.55 LF 0.35 LF 0.15 LF 0 LF

Top Layer Salts and Wilting Upon Irrigation Especially Critical in Subirrigation (from Todd & Reed 1998)

Leaching & Salt Removal From Media New Guinea Impatiens ‘Blazon’ in Subirrigation (from Todd & Reed 1998)

Determination of Soluble Salt Toxicity Limits “Shoot Gun” Approach

Plant Response to 24 Texas Water Sources (from Kent & Reed unpubl)

Growth Versus EC with 24 Water Sources Vinca ‘Apricot Delight’ Grown in Subirrigation (from Kent & Reed unpubl)

Growth Versus EC with 24 Water Sources Vinca ‘Apricot Delight’ Grown in Subirrigation (from Kent & Reed unpubl)

Growth Versus EC with 24 Water Sources Vinca ‘Apricot Delight’ Grown in Subirrigation (from Kent & Reed unpubl)

Growth Versus Na + Cl with 24 Water Sources Vinca ‘Apricot Delight’ Grown in Subirrigation

Determination of Soluble Salt Toxicity Limits Studies on Individual Salts (cation + anion combinations)

Chrysanthemum Rose 0 mM 2.5 mM 0 mM 5 mM 7.5 mM10 mM 2.5 mM5 mM 7.5 mM10 mM Toxicity Limits to Sodium Bicarbonate (from Valdez, PhD)

RoseMumVinca Hibiscus ‘Mango Breeze’ Hibiscus ‘Bimini Breeze’ SPAD Index decrease Predicted m M NaHCO 3 10% % % % Predicted NaHCO 3 Toxicity Limit as a Function of Chlorosis (from Valdez, PhD)

Determination of Soluble Salt Toxicity Limits Studies on Individual Salts (cation + anion combinations) Problem With This Approach Do not know if the effect is due to the cation or the anion

Determination of Soluble Salt Toxicity Limits Separation of Anion and Cation Effects Using Mixture Experiments

½:0:½ Y 0:1:0 X 1:0:0 Z 0:0:1 ½:½:0 0:½:½ 2/3:1/6:1/6 1/6:2/3:1/6 1/6:1/6:2/3 1/3:1/3:1/3 Pure blends Tertiary blends Centroid Binary blends Mixture Experiment Design

Mixture-Amount Experiments to Separate the Na + and HCO 3 - Effect in Sodium Bicarbonate Na + tox./K + def.=-19% HCO 3 - effect=-15% Shoot Dry Mass (g) (from Valdez, PhD) 0 mM HCO3 7.5 mM HCO3

2.5 HCO mM total binary mixture 0 HCO 3 - Proportion of K + and Na + Na + =-19% HCO 3 - =-19% Shoot Dry Mass (g) Na + K+K+ Binary Mixture Experiments to Separate the Na + and HCO 3 - Effect in Sodium Bicarbonate (from Valdez, PhD)

Mixture-Amount Experiments To Separate Chloride, Bicarbonate and Sulfate Effects (from Kent & Reed unpubl)

Separation of Chloride, Bicarbonate and Sulfate Effects with Mixture-Amount Experiments 30 meq/l 30 meq/l 45 meq/l 45 meq/l 60 meq/l 60 meq/l Vinca ‘Pacifica Red’ in Subirrigation HCO 3 HCO3HCO3 ClCl Cl SO 4 Cation = Na (from Kent & Reed unpubl)

Mixture-Amount Experiments To Separate Chloride, Bicarbonate and Sulfate Effects 30 meq/l 30 meq/l (1,700 to 2,500 ppm) 45 meq/l 45 meq/l (2,300 to 3,400 ppm) 60 meq/l 60 meq/l (2,800 to 4,400 ppm) Vinca ‘Pacifica Red’ in Subirrigation HCO 3 HCO3HCO3 ClCl Cl SO 4 Cation = Na (from Kent & Reed unpubl)

ThanksThanks

EC of Soluble Fertilizers & Water Quality

HCO 3 - effect=-15% Na + tox./K + def.=-19% Separation of Sodium and Bicarbonate Effect Using Mixture Experiments (from Valdez, Ph.D. dissertation) gshootmass

Leaching & Salt Removal From Media New Guinea Impatiens ‘Illusion’ in Subirrigation (from Todd & Reed 1998)