Produced Water Quality Limits for Irrigated Agriculture Robert Flynn, Ph.D. Extension Plant Sciences, NMSU rflynn@nmsu.edu
Introduction Water Quality Affects Soil Productivity Crop Performance Poor Water Quality Can be managed Can be treated Start with: Irrigation Water Assessment Soil Test
What are we looking for? ph Salinity Specific Ion Effects Sodium Bicarbonate Chloride Boron Other
ρh = -log(h + ) Water ρh Acidic, Basic, or Neutral Normal Range 6.5 to 8.4 New Mexico (>7 ph <8.4) Best to measure immediately
Water Salinity Presence of dissolved salts Cations (Ca ++, Mg ++, K +, Na + ) Anions (HCO 3-, CO 3=, Cl -, SO 4= ) Measured as Electrical Conductivity (e.c.) ds/m or mmhos/cm TDS (mg/l or ppm)
EC w Examples Distilled Water 0 Artesia 1.6 Tularosa 2.5 Fort Sumner 4.1 Vinton, TX 4.3 Carlsbad 6.0 Hagerman 6.6 Lake Arthur 8.8
Interpreting ec w Degree of restriction on use None Slight - Moderate Severe <0.7 0.7 3.0 > 3.0 UNITS: mmhos/cm
Interpreting TDS Degree of restriction on use None Slight - Moderate Severe <450 450-2000 > 2000 UNITS: ppm or mg/l e.c. X 640 TDS
SAR: Sodium Adsorption Ratio Sodium (Na) Calcium (Ca) & Magnesium (Mg) Na disperses clay particles in soil (bad) Ca & Mg bring clays into aggregates (good)
Sodium level (SAR) Both the amount of salts and the kind of salts affect soil structure 50 40 30 Dispersed soil 20 10 0 Aggregated soil 0.5 1.0 1.5 2.0 2.5 3.0 Electrical conductivity (ds/m)
Interpreting SAR & EC w Degree of restriction on use None Slight - Moderate Severe SAR = 0 3 & EC w = >0.7 0.7-0.2 <0.2 SAR = 3-6 & EC w = >1.2 1.2 0.3 <0.3 SAR = 6-12 & EC w = SAR = 12-20 & EC w = SAR = 20-40 & EC w = >1.9 1.9 0.5 <0.5 >2.9 2.9 1.3 <1.3 >5.0 5.0 2.9 <2.9
Specific Ion Effects - SAR Degree of restriction on use None Slight - Moderate Severe Surface Irrigation <3 3-9 >9
Specific Ion Effects: Cl - Degree of restriction on use None Slight - Moderate Severe Surface Irrigation (meq/l) <4 4-10 >10 meq Cl - /l = ppm/35.5
Irrigation & Na+, Cl Surface Irrigation Most woody species are sensitive to sodium and chloride Most annual species are not sensitive Overhead irrigation + low humidity Na+ and Cl- may be absorbed through the leaves of sensitive plants.
Crop Tolerance to Na + & Cl - 5 10 meq/l 10 20 meq/l >20 meq/l Grape Alfalfa Cauliflower Pepper Barley Cotton Potato Corn Sugarbeet Tomato Cucumber Sunflower Safflower Sesame Sorghum
Grape Tolerance to Cl - (meq/l) Grape RS or CV Root Zone Irrigation water Salt Creek, 1613-3 40 27 Dog Ridge 30 20 Thomson seedls 20 13.3 Perlette 20 13.3 Cardinal 10 6.7 Black Rose 10 6.7
Specific Ion Effects Boron Degree of restriction on use None Slight - Moderate Severe ppm <0.7 0.7 3.0 >3.0
Crop Tolerance to Boron (ppm) Very Sensitive (<0.5) Blackberry Sensitive (0.5 0.75) Grape Pecan Onion Less Sensitive (0.75 1) Wheat Peanut Moderately Sensitive (1-2) Pepper, red Potato Moderately Tolerant (2 4) Corn Squash Tolerant (4 6) Sorghum Tomato Alfalfa Very Tolerant (>6) Cotton Asparagus
Specific Ion Effects Bicarbonate (HCO 3- ) Degree of restriction on use None Slight - Moderate Severe meq/l <1.5 1.5 8.5 >8.5 meq HCO 3 - /l = ppm/61
Drip Irrigation Concerns
Clogging Hazards Clogging caused by: Physical Chemical Biological
Size of selected particles Coarse Sand: 0.5 1.0 mm Fine Sand: 0.1 0.25 mm Silt: 0.002 to 0.05 mm Clay: <0.002 Bacteria: 0.0004 to 0.002 Virus: <0.0004
Filtration Sized to remove particles 1/10 the size of the smallest emitter opening. Individual silt, clay, and bacteria can pass through filtration and emitters However, conglomeration occurs especially from bacterial glues Can t filter all the particles, so Flushing the system is important
Total Suspended Solids (TSS) Level of Concern Low <50 ppm (mg/l) Moderate 50 100 ppm (mg/l) High >100 ppm (mg/l)
Total Dissolved Solids (TDS) Level of Concern Low <500 ppm (mg/l) Moderate 500 2000 ppm (mg/l) High >2000 ppm (mg/l)
Chemical Precipitation Hazards ρh Low <7.0 Moderate 7.0 8.0 High >8.0 $12 - $18 $5 - $90
Chemical Precipitation Hazards Iron (Fe) Low <0.2 ppm (mg/l) Moderate 0.2 1.5 ppm (mg/l) High >1.5 ppm (mg/l) With sulfide >0.1 mg/l can get a black sand like material.
Chemical Precipitation Hazards Manganese (Mn) Low <0.1 ppm (mg/l) Moderate 0.1 1.5 ppm (mg/l) High >1.5 ppm (mg/l) In presence of sulfides can form a black, sand-like insoluble precipitate.
Chemical Precipitation Hazards Hydrogen sulfide (H 2 S) Low <0.1 ppm (mg/l) Moderate 0.1 2.0 ppm (mg/l) High >2.0 ppm (mg/l)
Chemical Precipitation Hazards Bicarbonate & ph (above 7.5) Low <1.5 meq/l Moderate 1.5 2.5 meq/l High >2.5 meq/l o Can Cause Lime Scale o White film around emitters o White precipitate in flush water
rflynn@nmsu.edu