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