Irrigating Turf With Effluent (Salty) Water by James A. McAfee, Ph.D. Extension Turfgrass Specialist Texas AgriLife Extension Service Dallas, Texas
Presentation Objectives Define Reclaimed Water Discuss Pro s and Con s of Using Reclaimed Water Discuss Testing for Irrigation Water Quality Discuss Problems Caused by Excess Salinity and/or Sodium Discuss Management Programs for Salinity Affected Soils
Reclaimed Water Reclaimed Water: wastewater effluent urban water reuse recycled water Additional Terms: gray water black water rainharvesting
RainHarvesting
Why Increased Interest in Using Reclaimed Water for Turfgrass Save potable water supply Avoid water restrictions Cost savings? Addition of turfgrass nutrients
Water Restricted Due to Drought Conditions
Concerns with Using Reclaimed Water for Sports Fields Water quality Irrigations system needs Applications restrictions/monitoring Continuous supply, even if not needed Soils
Reclaimed Water (treatment stages) Primary Secondary Tertiary
Irrigation System (New/Retrofit)
Important to Have Filters on Irrigation System
Posting Fields Using Reclaimed Water
Restrictions/Monitoring Hours of irrigation determined by city usually nighttime only Daytime irrigation generally have to have someone on site to monitor fields Special irrigation needs: overseeding watering in preemergent applications watering in insecticide application (grubs)
Excess Reclaimed Water
Salinity/Sodium Soil Problems
Testing Reclaimed Water Testing by wastewater producers: Biological oxygen demand (BOD) turbidity bacterial counts (pathogens) Agronomists/Horticulturists: electrical conductivity (ECw ) sodium adsorption ratio (SAR) carbonates, bicarbonates
Irrigation Water Quality Guidelines Potential problems: Salinity Ecw (conductivity) TDS Specific ion toxicity Na Cl B carbonate, bicarbonate levels Nutrients (N, P, K, Ca, Mg, micros) ph
SALT LEVELS IN IRRIGATION Hazard Class ECe (dsm-1) TDS (ppm) low < 0.75 < 500 medium 0.75-1.5 500-1,000 high 1.5-3.0 1,000-2,000 very high > 3.0 > 2,000
Field Salinity Meter
Other Potential Sources of Salts Soil minerals Well water Lakes Fertilizers (small) Flooding
Sodium Adsorption Ratio (SAR) relationship between Na, Ca, Mg in water measured in meq/l 10 meq/l or less, okay for irrigation purposes 18-26 meq/l, could be problems with Na accumulation in soil > 26 meq/l, don t use if at all possible
Residual Sodium Carbonate (RSC) Relationships between carbonates/bicarbonates and calcium/magnesium in water Formula: RSC = (CO3 + HCO3 ) ( Ca + Mg ) RSC: 0 to 1.25 meq/l, safe for irrigation 1.25 to 2.5 meq/l, marginal for irrigation > 2.5 meq/l, not suitable for irrigation
SALINITY TOLERANCE OF POPULAR TURFGRASSES (Turgeon, 2002) HIGH (Cool Season) (Warm Season) Tall fescue Perennial ryegrass Fine fescues Creeping bentgrass Kentucky bluegrass Rough bluegrass Colonial bentgrass Seashore Paspalum St. Augustinegrass Zoysiagrass Bermudagrass Buffalograss Centipedegrass Bahiagrass LOW
Managing Sports Fields With Salinity/Sodium Issues Drainage!!!!!!!!!!!!!!!!
Install Drainage System (leaching salts)
Turfgrass Irrigation
Football Field Audit Zone Precipitation Distribution Rate Uniformity 1 0.72 67 2 0.29 44 3 0.36 71 4 0.39 56 5 0.45 32 6 0.51 59
Leaching Requirement (salts present in irrigation water) LR = ECw /5ECe - Ecw Ecw = electrical conductivity of water Ece = soil level that starts affecting plant growth by at least 10%
Using LR to Calculate Irrigation Needs (Example) El Paso: 9 inch deficit for month of June equals 2.25 inches per week deficit crop coefficient of 60% need 1.35 inches of water per week assume a LR of 15% 15% X 1.35 =.2 inches Total weekly irrigation needs equals: 1.35 +.2 = 1.55 inches per week
Aerification Practices
Steps to Improve Turfgrass in Salt-affected Soils Regular testing of water source and soils Restrict use of poor quality water Select salt tolerant turfgrasses Leaching of salts and maintaining drainage Intensive cultivation practices Modifications with soil and water amendments Adjusted cultural practices
Other Cultural Practices Fertilization program Mowing progam
Case Study
Irrigation Water Source
Water Analysis Report Analysis Results Degree of Restriction Salinity Ecw (ds/m) 0.937 slight TDS (mg/l) 600 slight SAR 34 very severe Chloride (ppm) 39 low Boron 0.61 low RSC 6.17 very severe level
Water Analysis Report (continued) Analysis Results Lbs. Nutrient per (ppm) acre-foot of water* Nitrate-N.12.001 Phosphorus.23.014 Potassium 4.25 Calcium 2.125 Magnesium 1.0625 * one acre-foot of water equals 325,000 gals.
Soil Test Report (same site) Analysis Results Rating ph 8.9 Very high Phosphorus 1,626 ppm Very high Potassium 343 ppm high Calcium 15,204 ppm Very high Magnesium 188 ppm high Salinity 924 slight Sodium 1,465 ppm high Boron 3.92 ppm high
Rebuild Field
Sideline Drains
Adding Sand ( 7 inch depth )
Planting Big Roll Sod
First Home Game Preparation
Summary Using reclaimed water, always check source Drainage is the key to managing salinity and/or sodium problems Test water source and soils on a regular basis