Irrigation Strategies for

Water-Short Years or

Efficient Water Use

Northern Utah Water Conference

Logan, Utah

April 2, 2014

Presentation by

L. Niel Allen

Extension Irrigation Engineer

Definition of Water Use Efficiency

Yield per unit of water applied (example tons/acre-foot of

applied water)

Yield per unit of crop ET (example tons/acre-foot of ET)

Yield or production per unit of water diverted (incorporates

irrigation conveyance and distribution)

Yield per unit of precipitation (incorporates practices that reduce

precipitation runoff and deep percolation)

When are Irrigation Strategies for Improved

Water Use Efficiency Important?

Limited irrigation water

supplies

Allocation of water

between different crops

High irrigation water costs

Drought

Always

Presentation Overview

Irrigation System Improvements

Strategies to improve water use efficiency

General – Irrigation Scheduling

Alfalfa

Small Grains

Pasture, vegetables, fruit

Safflower

Strategy – Improve Irrigation System

Coefficient of Uniformity (Sprinklers)

Irrigation

Uniformity

Yield

Uniformity

The yield impact is the

obvious. Some yield impacts

are as real but not as

obvious.

Irrigation Depth Distribution (80%

Coefficient of Uniformity)

0

5

10

15

20

25

30

Irri

gati

on

Dep

th (

in)

Irrigation Depth Distribution (80% Coefficient of Uniformity)

Average Irrigation of 15 inches

0

5

10

15

20

25

30

0 10 20 30 40 50 60 70 80 90 100

Irri

gati

on

Dep

th (

in)

Area Receiving less than Indicated Depth (%)

Irrigation Depth Distribution

50 % of Area Fully Irrigated

CU=70% CU=80%" CU=90%

Assumes ET from Irrigation of 15 inches

For 15 inches of irrigation water (at 5 acre-inches/ton)

2.72 tons/acre of alfalfa for 90% uniformity

2.53 tons/acre of alfalfa for 80% uniformity

2.39 tons/acre of alfalfa for 70% uniformity

0

5

10

15

20

25

30

35

40

45

0 10 20 30 40 50 60 70 80 90 100

Irri

gati

on

Dep

th (

in)

Area Receiving less than Indicated Depth (%)

Irrigation Depth Distribution

75 % of Area Fully Irrigated

CU=80%" CU=90% CU=70%

For the same yield it takes about

16 inches with a 90% uniformity,

18 inches for a 80% uniformity, and

22 inches for a 70 percent uniformity.

Efficient Water Use for all Crops Improve Irrigation System Uniformity (minimize deep

percolation)

Replace sprinklers, gaskets, and fix leaks

Upgrade irrigation system

Level fields to uniform and proper grade

Adjust furrow or border flow rate

Irrigation Scheduling (minimize crop stress and deep percolation)

Crop Rotation

An excellent farmer told me - The best thing about growing green beans is the crop of wheat that follows.

Shallow rooted crops (onions, beans, potatoes, etc.) followed deep rooted crops (small grains, safflower, field corn).

10

Basic Principles Alfalfa

Alfalfa uses water is most efficient during spring growth (1st and perhaps 2nd cutting).

About 5 acre-inches of ET per ton (1st cutting)

About 7 acre-inches of ET per ton (later cuttings)

Under-irrigation results in higher irrigation efficiencies (slight deficit irrigation)

Better to stop watering alfalfa than to just keep it a dull green with little or no growth.

Most alfalfa varieties will go into dormancy with no long term impact.

Alfalfa is generally considered drought tolerant.

11

Basic Principles for Alfalfa (Continued)

Focus on most productive alfalfa land (best soils, best

alfalfa stem density, least weeds, youngest alfalfa, best

irrigation systems, best variety).

Focus on land with most efficient irrigation application.

Extra water does not produce extra yield.

Enough but not extra

12

Limited Irrigation of Alfalfa in the Great Plains and Intermountain West

Troy Bauder, Neil Hansen, Brad Lindenmeyer, Jim Bauder, and Joe Brummer

13

Irrigation Strategy for Wheat or Barley

Don’t stress your crop, but no need to have a full soil moisture profile at harvest.

It takes about 3 inches from soft dough to harvest.

In general you can stop irrigating at soft dough. Another irrigation of about 1 inch may be needed.

An advantage of a pivot over wheel line is that you can maintain the entire field near field capacity so that at soft it doesn’t take a week or more to irrigate.

Use irrigation scheduling

14

Other Important Considerations (Small grains)

Soil tillage to reduce runoff and soil moisture evaporation

Planting dates (plant early as possible in spring – fall is

better for wheat)

Irrigation scheduling

Variety has an impact on yield and water use efficiency.

Soil fertility has an impact on yield and water use

efficiency. Water is used more efficiently when nutrients

are available.

15

Last Irrigation of Wheat Information

0

5

10

15

20

25

1-Apr 1-May 31-May 30-Jun 30-Jul 29-Aug

ET

(in

ches)

Water Use and Stages of Winter Wheat

Spring growth

Jointing

Boot Stage

Flowering

Dough

Maturity

Harvest

Milk

Stop Irrigation with Full Soil Moisture Profile

16

Scheduling the Last Irrigation on Wheat and Barley

Howard Neibling and Zahid Qureshi, University of Idaho

17

Pasture Early water is the most important (cool season grasses).

Provide proper fertilization

Don’t over graze.

Consider the variety of grass if you are in a deficit irrigation condition.

Bromegrass and wheatgrass were more drought tolerant than tall fescue or orchardgrass, but they didn’t tolerate full-season irrigation, and when fully irrigated their stands were dramatically reduced. Orchardgrass tolerated a single season of deficit irrigation but over several years it didn’t persist as well as tall fescue. (Orloff and Putnam, UC 2010)

Irrigation Scheduling

18

Vegetables

Best Strategy is to have an irrigation system with good

uniformities and flexibility.

Many high value vegetable crops (i.e. green beans, fresh

peas, sweet corn) are harvested during a high water use

period. Don’t stress these crops prior to harvest time.

Maintain adequate soil moisture, especially during critical

development periods.

19

Fruit Production

Best Strategy is to have an irrigation system with good

uniformities and flexibility.

Consider micro-irrigation

Many high value crops are harvested during a high water

use period, so don’t sacrifice quality due to irrigation

Maintain adequate soil moisture.

20

Safflower Irrigation Research

Questions Investigated:

1. When and how often should safflower be

irrigated?

2. At what growth stage should irrigation

be terminated? and

3. How does irrigation impact Alternaria

leaf spot?

Greenville Utah Agriculture Experiment Farm,

North Logan, Utah (field in 2011)

Irrigation Plot Layout

Safflower Irrigation Research (2013) Greenville Farm

First Irrigation

A B C D E F

1 0 1 2 0 3 0

2

3 0 1 3 0 3 1

4

5 2 3 1 2 3 0

6

7 1 1 3 Treatments

8 0 - No irrigation.

9 2 2 2 1 - One irrigation (elongation).

10 2 - Two irrigations (elongation and branching).

11 3 - Three irrigations (elongation, branching, flowering).

12 Plots are 50 feet by 210 feet

13

Irrigation buffer - not used

Irrigation treatment

1800 North

80

0 East

Sprinkler Line

Main Line

2013 Cropping Information

Pre-plant fertilizer application of 70 lbs N per acre

April 22: Treated with Sonalan for weed control (2

pints per acre)

April 25: planted

Seeding rate of 20 lbs per acre

Variety is #208

May 7: cotyledon leaf stage

June 11-14 : 1st irrigation (2.96 inches net avg.)

June 28 – July 2: 2nd irrigation (3.27 inches net avg.)

July 18-19: 3rd irrigation (3.27 inches net avg.)

Cropping Information

August 3: Obtained imagery of field.

August 9: Fungicide application on half of each plot

(Quadris Flowable) at 12 oz. per acre and (Exit

Activator Adjuvant) at about 6 oz. per acre.

Oct 9: Harvested 9 of 48 sub-plots (a portion of the

east side) Combine broke and then it rained.

Oct 21: Harvested remainder of plots

Total yield of field (all buffers and plots) was 38,000 lbs

or about 2,990 lbs. per acre

Data Collected

Weather data from USU Greenville Farm station

Initial soil moisture samples taken at 3 locations on

May 10.

Soil moisture samples taken every two weeks at 6

locations June 7 through September 3.

Yield data for plots

Oil content, bushel weight, moisture percent

Seed Color Score – color scale, dark ends, papus,

immature seeds, slight yellowing, sprouting

May 7 May 21

May 29 June 7

June 17 (first Irrigation June 11) June 24

July 9 (2nd Irrigation on June 28) July 9 (two irrigations)

July 9 (no irrigations)

July 9 (two irrigations, slight Alternaria leaf spot

July 15

Differences in maturity, branching, and

number of seed heads

July 15 (2 irrigations, 1 irrigation, and no irrigation)

July 18 (third and last irrigation)

July 22 (3 irrigations) July 22 (no irrigations)

July 30 (3 irrigations, Fungicide was applied August 9)

July 30 (no irrigation

east side)

No signs of

Alternaria

False Color Image (red is well irrigated)

August 3 (Aerial Photo and

Irrigation level)

0

0

2

1

2

0

0

0

0

2 2

22 3

3

3

3

3

3

1

1

1

1

1

Difference between area treated with and

without fungicide

September 19

October 18 (harvest)

Safflower Yields

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

4,500

0 2 4 6 8 10 12

Yie

ld (

lbs.

/a

c.)

Irrigation Amounts (inches)

Safflower Yield for Irrigation Levels

Average Yields for by Irrigation Levels

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

I-0 I-1 I-2 I-3

Yie

ld (

lbs/

acr

e)

Irrigation Level (0 to 3 Irrigations)

Safflower Yields v Number of Irrigations

Greenville Farm 2013

2013 Greenville Farm Rain and Irrigation

0

0.5

1

1.5

2

2.5

3

3.5R

ain

an

d I

rrig

ati

on

(in

ches)

2013 Greenville Farm Safflower Study (Rian and Irrigation)

0

2

4

6

8

10

12

14

16

18

20

ET

(in

.)Total Cumulative ET for Irrigation Levels Safflower 2013based on Soil

Moisture Measurement (top 5 feet), Precipitation and Irrigation

I-3 I-1 I-0 I-2 I-1 I-2

Irrigation, Water Use and Yield

LocationNo.

Irrigations

Irrigation and

Precipitation

(inches)

Soil Water

Depletion

(inches)

ET

(inches)

Yield

(lbs/acre)

1 - E 3 12.41 6.27 18.68 3,978

2 - E 1 5.05 7.89 12.94 1,724

3 - E 0 2.02 6.65 8.68 1,705

4 - W 2 8.26 9.71 17.97 3,300

5 - W 1 6.16 8.85 15.01 2,422

6 - W 2 9.17 9.79 18.96 3,919

Summary

The number of irrigations made effected the yields

with a high significance level. There was the least

difference in yield moving from 2 to 3 irrigations.

The alternaria leaf spot disease was not a significant

factor in the yield.

The fungicide treatment resulted in improvement dark

ends.

In 2013 there was very little rain in June, July, and

August while the was maturing. The results could

change during a year with higher precipitation.