Irrigation Management and Technologies to Improve Water Use Efficiency and Potential Application in Avocado Production Khaled M. Bali, Ben Faber, and Daniele Zaccaria UC Kearney Agricultural Center, UCCE-Ventura County, and UC Davis kmbali@ucanr.edu 559-646-6541
Management Practices to Cope with Limited Water Supplies in California: - Improve irrigation efficiency (pressurized systems or higher efficiencies in existing systems) - Regulated deficit irrigation (alfalfa and other crops) - New cropping systems (lower water use crops or changing practices) - Other practices (land fallowing for water transfer, etc) - Irrigation management (irrigation scheduling and technologies that can save water)
Irrigation Water Management - Applying the right amount of water to meet crop water requirements (in/irrigation) - Timing of irrigation events (frequency, days between irrigations) - Applying the water uniformly (efficiency)
Irrigation Scheduling - Simple approach (Water budgeting using ETo and crop coefficients) - Soil moisture measurement (requires extra work, soil sampling, soil moisture sensors, dataloggers, etc) - Plant-based approach (temperature, sap flow, etc) - A combination of the above three methods - Advances in irrigation technology and methods to estimate ETc (Warning: Too Much Information)
How Much Water do I need to Apply? - Need to know crop water use (ETc) since last irrigation - ETc from (Reference evapotranspiration and crop coefficient) - Typical application rates (vary widely depending on soil type): - Surface: ~ 3-4 in/irrigation (much higher rate for light soils) - Sprinkler: ~ 0.5-1.2 in/irrigation - Drip: ~ 0.5 in/irrigation
Crop Water use: Soil moisture Total soil water Plant Available water Saturation (S) Field Capacity (FC) Yield threshold (YT) Permanent wilting point (PWP) Oven dry
Why do we irrigae: replenish the amount of water used by the crop (ET C ) since the last irrigation Crop ET = Reference ET x Crop Coefficient ET C ET O k C Also used in system Design: Max Irrigation depth to be applied (D GMAX ) D ETc Eff D PEAK G MAX inches / irrigation System Eff. APP APP Gravity 70-85% Drip 85-90% Micro-sprinkler 80-90% Sprinkler 70-90%
ETc and ETa
CIMIS (Map) - Simple table to estimate ETo based on historical data - Data based on historical average ET - Good estimates but doesn t account for climate variability - Not location specific (zones) CIMIS (website) http://wwwcimis.water.ca.gov/ - Easy to access, provide historical and recent data. - More accurate estimate from CIMIS stations close to the farm data
ETo: Spatial CIMIS Couples remotely sensed data from GOES satellite with point measurements from CIMIS stations to estimate ETo. Provides daily maps of ETo at 2-km grid. Released to the public in September 2009. Source: DWR 2016 ETo Equation 900 0.408 ( Rn G) u2( es ea) ETo T 273 (1 0.34u ) 2
ET o - accounts for weather Solar radiation, humidity, temperature, wind K c - accounts for crop light absorption canopy roughness physiology age surface wetness (irrigation system)
Crop Coefficient K c ET c - measured ET ET c o ET o - estimated
Theoretical Mean K c Values
Percentage of Season 1.20 0 20 50 100 CROP COEFFICIENT (K c ) 0.80 0.40 0.00 Initial Rapid Midseason A B C GROWTH DATE E
Comments about crop coefficients for Hass Avocado on Mexican Seedling Rootstocks. January 10, 2007 J.D. Oster and M.L. Arpaia University of California Riverside, CA. James.oster@ucr.edu The comments begin with the cover page and abstract of a paper accepted on January 9, 2007 for publication by the J. Amer. Soc. Hort. Sci. Kc~0.86* fraction of shaded area
Table 1. source: Growing avocados annual water requirements Department of Primary Industries and Regional Development (DPIRD) Government of Western Australia https://www.agric.wa.gov.au/water-management/growing-avocados-%e2%80%93-annual-water-requirements
Precision Irrigation: NDVI Mean (Normalized Difference Vegetation Index 0-1) ~ 285 Sunflower varieties at DREC 2016 (Kc is related to NDVI) 04/12/2016 04/21/2016 05/03/2016 05/12/2016 05/13/2016
Tulare County- Almond Variable Rate Irrigation (VRI)- NDVI VRI- 1 acre zone System design: irrigate 1 zone (1/36 of the field) or irrigate up to 36 zones all at once System design to meet peak energy demand/pricing (irrigate when cost of energy is low) Historically peak hours were defined as the hours between 12pm- 6pm (PG&E, 2016). Proliferation of solar generation in California is forcing those peak hours to shift to later hours in the day (4pm- 9pm) with Some over generation during the day Source: Aghajanzadeh and English, 2018
ETc= ET* Kc New methods for ETc and ETa Current/latest : Tule, Arable Future: ETa maps & Google
Arable Mark https://www.arable.com/
DRAFT Alfalfa cumulative ET Tule vs. Eddy Covariance (Davis - 2016)
Consequences of improved on-farm efficiency and the future of irrigation systems in CA Improved efficiency - Salinity buildup - Less water for groundwater recharge Practical options - Dual irrigation systems (for irrigation and surface system for GW recharge) - Design to optimize profit (consider the cost of energy, GHG emission, value of water, etc) - Modernization of irrigation districts (SSJID- Pressurized, Turlock ID- Active control, Oakdale ID- Storage and automated control, CVWD- GW recharge)
IMPROPVING ON-FARM IRRIGATION EFFICIENCY 1. Improving efficiency of ALL irrigation systems (not just focus on pressurized systems) 2. Reduce irrigation labor cost through automation (5.5 hrs/ in Imperial Valley to 9 hrs/ac in Sacramento Valley) 3. Better understanding of crop water use (Kcs for various crops/regions) 4. Utilization of technology for irrigation scheduling and precision irrigation 5. Consider deficit irrigation to address water shortages (Water transfer, drought, SGMA, and limited water supplies, etc) 6. Improving irrigation district system efficiency and flexibility (on-demand, demand/response, pressurized irrigation water, down stream control or active control, etc) 7. Assessing the water, energy, pollution and GHG footprints of these different production systems
Thank You
Example: Crop Water Use: ETc = ETo x Kc If ETo was 0.6 inches since my last irrigation (7 days ago) and my average Kc over that period was 0.5 then: ETc = 0.6*0.5=0.3 inches So I need to apply a NET of 0.3 inches of water to replace the crop water use of last week
Crop Water Use: - Water requirements = ETc / AE -AE= Application Efficiency or Distribution uniformity (70-90% for Surface-Sprinkler- Drip Irrigation), if AE is 80% then Water requirements= 0.3 /0.80 = 0.38 inches of gross application
Irrigation Runtime (microsprinkler): =Gross amount of application (in)/application rate (in/hr) If the average application rate is 0.10 in/hr Then Irrigation time = 0.38/0.10= 3.8 hrs