Practical Irrigation Scheduling, Technology & Deficit Irrigation. Katherine Pope, Farm Advisor Sac, Solano & Yolo Counties

Practical Irrigation Scheduling, Technology & Deficit Irrigation Katherine Pope, Farm Advisor Sac, Solano & Yolo Counties

Irrigation Scheduling: Demand and Supply Demand = Evapotranspiration Supply = Storage, Precip & Irrigation

Irrigation Scheduling: 5 things you need to know Demand Supply 1) ETc 2) Soil texture 3) Rooting depth or volume 4) Drip / Micro Emission Rate (gph) 5) Emitters per acre

Demand: Evapo-Transpiration Evaporation: Wetted area Transpiration: Leaf area

Stomata let water out to 1) Cool the plant and 2) Allow CO 2 in ( sugars) Electron micrograph of stomata on underside of leaf. B. Sanden

Demand: Evapo-Transpiration Evaporation: Wetted area Transpiration: Leaf area Tree size Spacing Stage of dev

Daily, Weekly Demand: ETc Calculating ET for crops: ET crop = ET o * K c * E f ET o = reference crop (non-stressed tall grass) ET K c = crop coefficient for a given stage of growth as a ratio of grass water use. May be 0 to 1.3, standard values are good starting point. E f = an environmental factor that can account for immature permanent crops and/or impact of salinity. May be 0.1 to 1.1, determined by site. B. Sanden

Daily, Weekly Demand: ETc ETo with CIMIS Weather Station Courtesy of Mark Anderson, DWR

Daily, Weekly Demand: ETc 1.2 Sac Valley Almonds Kc 1 0.8 Kc 0.6 0.4 0.2 0 1/1 4/11 7/20 10/28 Date A. Fulton

Weekly Demand: ETc

Irrigation Scheduling: 5 things you need to know Demand 1) ETc 2) Soil texture Supply

Supply: Available Soil Water Holding Capacity Saturation Field Capacity Perm Wilting Point terragis.bees.unsw.edu.au Monitoring Soil Moisture (ANR 21635)

Supply: Available Soil Water Holding Capacity Saturation Field Capacity Perm Wilting Point Field Capacity terragis.bees.unsw.edu.au Monitoring Soil Moisture (ANR 21635)

Supply: Available Soil Water Holding Capacity Saturation Field Capacity Perm Wilting Point Field Capacity Available Soil Moisture Perm Wilt terragis.bees.unsw.edu.au Monitoring Soil Moisture (ANR 21635)

Supply: Available Soil Water Holding Capacity Saturation Field Capacity Perm Wilting Point Avail Soil Field Moist Capacity 50% ASM Perm Wilt terragis.bees.unsw.edu.au Monitoring Soil Moisture (ANR 21635)

Supply: Available Soil Water Holding Capacity ET Soil Text Field Capac Perm t Wilt Pt (15 b) Avail Soil Moist 50% Avail in/ft in/ft in/ft in/ft Sand 1.2 0.5 0.7 0.35 Silt loam 3.6 1.8 1.8 0.9 Clay 4.8 2.6 2.2 1.1 Avail Soil Field Moist Capacity Perm Wilt 50% ASM Daily Loss Monitoring Soil Moisture (ANR 21635)

Supply: Available Soil Water Holding Capacity Photos: Blake Sanden

Irrigation Scheduling: 5 things you need to know Demand Supply 1) ETc 2) Soil texture 3) Rooting depth

Supply: Root Structure Depth of Main Root Zone = 3-18 inches Depth (inches) 0-4 4-8 8-12 12-16 16-20 20-24 24-28 28-32 32-36 Figure: A. Olivos, P. Brown

Irrigation Scheduling: 5 things you need to know Demand Supply 1) ETc 2) Soil texture 3) Rooting depth 4) Drip / Micro Emission Rate (gph) 5) Emitters per acre

Irrigation Scheduling: Hourly Rate of Water Application for Duration and Frequency Determine Average Emission Rate from drip / microsprinklers Count number of drippers or (micro)sprinklers per acre Know 1.0 acre-inch volume of water equals 27,154 gallons Calculation for Drip and Microspinklers rated in gph: Average Emission Rate (gph) X Number of drippers or micros per acre 27,154 = (inch/hour)

Irrigation Scheduling: Hourly Rate of Water Application for Duration and Frequency Determine Average Emission Rate from drip / microsprinklers Count number of drippers or (micro)sprinklers per acre Know 1.0 acre-inch volume of water equals 27,154 gallons Calculation for spinklers and mini-sprinklers rated in gpm: Average Emission Rate (gpm) X Number of (mini)sprinkler s per acre X 60 27,154 = (inch/hour)

Irrigation Scheduling: 5 things you need to know Demand Supply 1) ETc 2) Soil texture 3) Rooting depth 4) Drip / Micro Emission Rate (gph) 5) Emitters per acre

Irrigation Scheduling: Supply > Demand Keep Supply Great Than Demand Soil Texture 50% ASM in/ft Sand 0.35 Silt loam 0.9 Clay 1.1 Depth (inches) 0-4 4-8 8-12 12-16 16-20 20-24 24-28 28-32 32-36

Irrigation Scheduling: Supply > Demand Keep Supply Great Than Demand Soil Texture 50% ASM in/ft Sand 0.35 Silt loam 0.9 Clay 1.1 Depth (inches) 0-4 4-8 8-12 12-16 16-20 20-24 24-28 28-32 32-36 Silt Loam: 0.9 in / ft * 2 ft = 1.8 in 0.9 in

Irrigation Scheduling: Hourly Rate of Water Application for Duration and Frequency Determine Average Emission Rate from drip / microsprinklers Count number of drippers or (micro)sprinklers per acre Know 1.0 acre-inch volume of water equals 27,154 gallons Calculation for Drip and Microspinklers rated in gph: 25 Average Emission Rate (gph) X 110 Number of drippers or micros per acre 27,154 = 0.1 (inch/hour)

Irrigation Scheduling Demanded Re-Supply Run Time 0.9 inches lost 0.1 inches / = 9 hour applied / hour Saturation More than 9 hour

Irrigation Scheduling Run Time Per Irrig. Re-Supply Re-Supply Per Irrig. 0.1 inches 16 hour x = 1.6 inches applied / hour

Irrigation Scheduling Run Time Per Irrig. Re-Supply Re-Supply Per Irrig. 0.1 inches 16 hour x = 1.6 inches applied / hour Demanded 3.2 inches lost Re-Supply Per Irrig. 1.6 inches / = 2 irrigations

Irrigation Scheduling: 5 things you need to know Demand Supply 1) ETc 2) Soil texture 3) Rooting depth 4) Drip / Micro Emission Rate (gph) 5) Emitters per acre

Irrigation Scheduling: Use Your 5 Things Weekly ETc Soil Textr x Depth 50% Avail Soil Moist Emission Rate x Emitters per Acre / 27,154 Resupply Rate If Weekly ETc less than 50% ASM: Weekly ETc / Resupply Rate = Run Time If Weekly ETc more than 50% ASM: Longest OK Run Time x Resupply Rate = Resupply per Irrig. Weekly ETc / Resupply per Irrig. = # of Irrig.

Why Should I Monitor the Soil and Plant? Increases Efficiency of Water Applications by: Determining proper timing of irrigation in a variable environment, Making sure water stays within the rootzone (and reducing application amounts if it doesn t), Applying stress at specific periods to reduce water use and provide disease control benefits D. Doll

Monitoring Applications Soil Based Monitoring Provides an idea on movement and depth of water within soil Able to identify duration of irrigations based on movement of water within the soil Hard to interpret when salt or disease comes into the picture Plant Based Monitoring Indicates plant stress levels, regardless of soil conditions; Useful in troubleshooting irrigation schedules, managing RDI; With exception of pressure chamber, not much work done in other systems; D. Doll

Soil Moisture Monitoring Tools Electrical Resistance Feel Method Capacitance/ TDR Neutron probe Tensiometer ANR Pub 21635 D. Doll

Soil Moisture Monitoring "Feel" Tensiometers Dielectric Sensors Electrical Resistance Neutron Probes Basic Operation Soil between fingers Measures the suction Measures dielectric constant Measures resistance Measures neutrons slowed by water Requirement for Calibration Experience Minimal Yes, soil dependent Moderate Yes, soil dependent Manual or Monitoring Frequency Manual, Once Automatic Automatic Automatic Manual, once Zone of Measurement Replacement, Maintenance Size of Auger bucket None 2" off of sensor Annual (check of vacuum and gauges), some require removal Affected by Salinity, Alkalinity None No Soil Type Most Suitable All All Common Companies Hortau, Irrometers About 1 from outside edge 1" off of sensor, less in heavy, wet soils 10" diameter Replace batteries, Annual Maintenance Annual, replacement every 3-7 years transport rules, annual radiation safety check Yes, but depends on sensor type Yes No Sand Sandy Clay Loam (Non-cracking Sandy Loam Clay Soils) All Decagon, Aquacheck, EnviroSCAN Watermarks Contracted Services More information: http://ucmanagedrought.ucdavis.edu/ Table: D. Doll

Comparison of Capacitance to Neutron Probe Water Content (total mm to 1.5 m depth) 425 PureSense 0-1.5m Weekly NP 0-1.5 m 400 375 350 325 300 275 250 225 2/1 2/22 3/15 4/5 4/26 5/17 6/7 6/28 7/19 8/9 8/30 9/20 10/11 11/1 D. Doll

Plant Based Monitoring Tools Pressure Chamber Aerial Imaging Dendrometers Sap Flow Sensors Source: http://www.dynamax.com D. Doll

Plant Based Monitoring "Look and Feel" Sap Flow Sensors Dendrometers Pressure Chamber Aerial Imaging Look at newer growth Measures Sap "flow" Measures Expansion, Contraction Measures Stem Water Potential Measures canopy temperature Basic Operation Requirement for Calibration Yes Yes Yes No Yes Monitoring Frequency Except when blinking Continuous Continuous Manual Manual Zone of Measurement Few trees Single Tree Single Tree Single to few trees Entire Orchard Replacement, Maintenance None Yes, 2-3 years Yes Minimal None Major Challenges Too Late Not refined for Almonds Lack of Calibration Time involved Not refined for Almonds Table: D. Doll Photo: dynamax.com

ANR Pub 8503

Regulated Deficit Irrigation during Hull Split 1) Speed up Hull Split 2) Reduce Hull Rot 3) Reduce Sticktights (Improve Harvestability) 4) Save Water SWP recommendation: -14 to -18 bars during hull split K. Shackel

Corning RDI Uneven % Hull Split Timing 2000 16 Aug 14 Sep 2001 Date Jul 13 Jul 27 Aug 13 East (silt) 2% 45% 100% East (Avrg SWP = -8.4 bars) 0% 40% West (gravel) 2% 55% 100% West (Avrg SWP = -14.1 bars) 23% 91% 2003 Date Aug 7 Aug 22 East (silt) 95% 100% West (gravel) 88% 100% K. Shackel

Irrigation 101 NOT ENOUGH HOW MUCH

DROUGHT: 2 Strategies Mild or Severe 0-15% reduction: Strategic Deficit Irrigation: applied during June/Hullsplit period 16% or greater reduction: Proportional Deficit Irrigation: Apply available water at the percentage of available ETc evenly through the season (Goldhamer et al., 2006)

Drought Strategies Explained Severe Deficit in this period will increase shriveled nuts Deficit in this period will decrease nut/fruit size Stress at any period reduces vegetative growth, affects future yield! Deficit in this period will increase texturing, decrease kernel weight Deficit in this period has minimal effects Deficit in this period effects fruit bud set

Outcomes of Different Strategies Full Irrigation (~44 applied) Full Irrig. until June, then No Water (~22 applied, 50% Deficit) 50% Proportional Deficit (~22 applied, 50% Deficit) Normal Size 15 nuts/18 grams Marketable Normal Size, Shriveled: 15 nuts/13.5 grams Reduced Marketability Small Size, Not Shriveled: 15 nuts/12.5 grams Marketable

Other Strategies to Conserve Water System Maintenance: Increase DU to decrease waste. 70% DU takes 22% more water to adequately irrigate than 90% DU Chemically Mow: Ground cover uses 20-30% more water. (Sacrifice: Compaction) Decrease exposed wetted surface. 6 hour set minimum.

Other Drought Points Stressed trees will flare mites, have earlier hull-spit Decrease Nitrogen rates if lower yields expected Expect reduced yields next year b/c of reduced bud growth and development this year. If severe, yields could take two years to recover.

RESOURCES ANR 3396 ANR Pub 21635 ANR Pub 8503 Free! http://ucmanagedrought.ucdavis.edu DU Testing Guidelines : http://micromaintain.ucanr.edu

Thanks! Questions?

Irrigation Scheduling: Matching Supply & Demand Soil Texture Field Capacity Soil Moisture Chart Permt Wilt Pt (15 bars) Available Soil Moisture 50% Avail Soil Moisture in / ft in / ft in / ft in / ft Sand 1.2 0.5 0.7 0.35 Loamy sand Sandy loam 1.9 0.8 1.1 0.55 2.5 1.1 1.4 0.7 Loam 3.2 1.4 1.8 0.9 Silt loam 3.6 1.8 1.8 0.9 Sandy clay loam 3.5 2.2 1.3 0.65 Sandy clay 3.4 1.8 1.6 0.8 Clay loam 3.8 2.2 1.6 0.8 Silty clay loam 4.3 2.4 1.9 0.95 Irrigation Scheduling Calculations: Weekly ETc Soil Textr 50% Avail Soil Moist, then 50% ASM x Root Depth 50% ASM in root zone Emission Rate x Emitters per Ac / 27,154 Resupply Rate If Weekly ETc less than 50% ASM in root zone: Weekly ETc / Resupply Rate = Run Time Ex: 0.9 lost / 0.1 applied per hour = 9 hour run time If Weekly ETc more than 50% ASM in root zone: Longest OK Run Time x Resup Rate = Resup per Irrig. Weekly ETc / Resupply per Irrig. = # of Irrig. per Week Ex: 16 hrs x 0.1 applied per hour = 1.6 per Irrigation 3.2 lost / 1.6 per Irrig. = 2 Irrig per Week Silty clay 4.8 2.4 2.4 1.2 Clay 4.8 2.6 2.2 1.1 Monitoring Soil Moisture (ANR 21635) Compiled Kat Pope, 2/26/15

Irrigation Resources ANR 3396 ANR Pub 21635 ANR Pub 8503 Free! http://ucmanagedrought.ucdavis.edu DU Testing Guidelines : http://micromaintain.ucanr.edu

Plant Based Monitoring "Look and Feel" Sap Flow Sensors Dendrometers Pressure Chamber Aerial Imaging Look at newer growth Measures Sap "flow" Measures Expansion, Contraction Measures Stem Water Potential Measures canopy temperature Basic Operation Requirement for Calibration Yes Yes Yes No Yes Monitoring Frequency Except when blinking Continuous Continuous Manual Manual Zone of Measurement Few trees Single Tree Single Tree Single to few trees Entire Orchard Replacement, Maintenance None Yes, 2-3 years Yes Minimal None Major Challenges Too Late Not refined for Almonds Lack of Calibration Time involved Photo: dynamax.com Not refined for Almonds Table: D. Doll

Whole Season Demand: Yield-Driven Light Interception Yield Potential 1% of light intercepted = 50 kernel pounds yield potential Figure & Research: B. Lampinen

Whole Season Demand: Yield-Driven Light Interception Photosynth + CO 2 Sugars Production Yield Potential Transpiration 1% of light intercepted = 50 kernel pounds yield potential ~0.7 inches water use Figure & Research: B. Lampinen

Whole Season Demand: Yield-Driven

Whole Season Demand: Ground Cover Ground Cover Also Uses Water ~35% PAR interception Needs ~25 of water ~40% PAR interception from trees plus 40% from grass = 80% total Needs ~56 of water B. Lampinen