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Irrigation Technology: Minimizing Use of Water and Maximizing Production
CONFERENCIA INTERNACIONAL EN RECURSOS HIDRICOS TARIJA- 2018
Charles West, Professor of Plant & Soil ScienceTexas Tech University, USA
How do we conserve water and be profitable?
Acuifero de OgallalaEstados Unidos
Crop distribution
USDA-NASS, 2016McGuire, 2014
Aquifer decline since 1950
Objective: Optimize use of groundwater in the Ogallala region to sustain food production and rural communities.
➢ Improve water-use efficiency through irrigation management technologies
➢ Promote adoption of irrigation scheduling
What is sustainability ?
• Economic profitability is always no. 1.
• Prolong the life of the water supply.
• Combination: Profitability with reduced
irrigation
Irrigate when needed, do not waste water
Efficiency
Potential Evapotranspiration (PET) drives water demand= Evaporation from soil + Transpiration from plant leaves
PET 223 cm
Precip. 46 cm
Diff. 177 cmDéficit
• Demonstrate how to reduce water use
• Identify profitable crop and irrigation systems
• Provide online tools for decision-making on irrigation timing and economic options
Texas Alliance for Water ConservationUniversity partners with producers
➢ Irrigation methods
➢ Types of crops
➢ Monitor the soil water
➢ Irrigate at less than PET
Sprinkler Subsurface Drip
FurrowDryland, pasture
Irrigation methods
Subsurface Drip
Spray – 80-85% Mobile Drip – 90% LEPA – 90-95%
Technology comparison for efficiency
% Efficiency Low Energy Precision Application
Precision Mobile Drip Irrigation
More economical to add to existing spray system than to
install subsurface drip.
Comparison of irrigation methods – recharge rate
Spray LEPA
Spray is slow to
wet the soil
LEPA is fast to
wet the soil
Comparison of Spray vs. LEPA – 3 years; algodón
SPRAY LEPA
Cotton lint yield kg/ha 1046 1200
Total costs $/ha 2314 2366
Net returns $/ha 141 447
Water applied mm 495 495
Water use effic. kg/m3 0.21 0.24
Water footprint m3/kg 4.7 4.1
Yates & Pate. 2014.
Farm Irrigation system
Irrigation amount cm
Yield kg/ha
Return $/m3
Return $/ha
1 Spray 29 1020 0.18 515
Drip 24 1340 0.32 744
Profitability of Spray vs. Drip Irrigation - Cotton
Farm Irrigation system
Irrigation amount cm
Yield kg/ha
Return $/m3
Return $/ha
1 Spray 29 1020 0.18 515
Drip 24 1340 0.32 744
2 Spray 44 1220 0.09 378
Drip 33 1520 0.38 1239
Profitability of Spray vs. Drip Irrigation - Cotton
Making the most of little water
United Sorghum Checkoff Program
Crop Yield kg/ha Irrig cm Profit/ha* Profit/cm
Sorghum 130 20 $ 613 $ 31
Maize 240 44 1184 27
Cotton 1430 33 831 25
* Gross return
Maize
1-May
Planting Dates
15-May
15-June1-June
Capacitance probe with soil moisture sensors
120 cm
Capacitance probe soil-moisture sensors:
Summary of soil water content
Rainfall Events
Drip Irrigations
June 1-August 14, 2013
Maize yield response to total water, rain + irrigation
0
0.1
0.2
0.3
0.4
0 30 60 90 120 150Days
Da
ily
Wa
ter
Use
(in
)
When to water? Example of sorghum
Maturity
GPD - 7
leaf
Boot Bloom
Grain Fill
United Sorghum Checkoff Program
Precision irrigation
Practices that increase water use efficiency
• Crops and new varieties with higher WUE
• Manage soil for high infiltration rate
• Irrigation type (drip or LEPA)
• Irrigate at <100% PET
• Variable rate irrigation by soil condition
• Diversify farming system with dryland, low,
and moderately irrigated crops
• High quality forages
Why forages and cattle?
•Native ecosystem is grassland.
• Perennials build soil organic matter, reduce soil erosion.
•Beef cattle and hay are high-value commodities.
•Require low water inputs.
Capitalize on using high-quality forages with low resource inputs.
Alfalfa and sweet clover seeded into grass
Alfalfa and sweet clover in grass, next year
Dryland Native – 4.5 ha
Dryland Teff – 1.7 ha OWB – 2.1 ha
Grass with no legume (12 head on 8.3 ha)
Native – 0.9 ha Teff – 0.2 ha
Alfalfa-tall wheatgrass – 0.9 ha
OWB-Legume – 2.1 ha
Grass with legume (8 head on 4.1 ha)
Animal liveweight gain per ha
Bars represent SE mean.
0
50
100
150
200
250
Year 1 Year 2 Year 3
LW
G h
a-1
(kg
ha
-1)
Grass-only Grass-legume
n = 3; P < 0.001
Water inputs Grass-only Grass + legume Δ %
Rain + irrigation + drinking 33 22 -34 %
Irrigation + drinking 3.3 2.4 -27 %
Water footprint in m3/kg beef gain
Why? Legume required slightly more irrigation,
but it increased animal gain 60% over grass alone.
Twice the protein content, more digestible energy.
Fixes N via symbiosis, so C and N footprints are also lower.
Muchas Gracias!
Funded by:
USDA-NIFA
USDA-SARE www.tawc.us