water efficiency in cool season hay production

WATER EFFICIENCY IN COOL SEASON HAY PRODUCTION

Caleb CarterUW Extension EducatorMaster Hay Grower ProgramLaramie, WYMarch 24, 2015

IMPROVING FLOOD IRRIGATION EFFICIENCY

Goal?

Active root zone

FLOOD IRRIGATION

• Efficient flood irrigation– Almost filling root

zone– Utilizing or

minimizing runoff

WHAT ABOUT THE SOIL?

“…and we can save 700 lira by not taking soil samples!”

The water balance

Web soil survey

Obtain info on:• Soil type• H2O capacity• infiltration

http://websoilsurvey.sc.egov.usda.gov/App/HomePage.htm

Available soil moisture

• Field Capacity• 50% Available

Water• Permanent

Wilting Point• MAD

Effects of irrigation on infiltration

Soil Texture

Basic Infiltration Rate (in/hr)

Fine sand 0.50 – 0.75Sandy loam 0.35 – 0.5Silt loam 0.25 – 0.40Clay 0.10 – 0.20

Management allowable depletion (MAD)

50%Take half, leave half…

…works for water too

GETTING DOWN TO BUSINESS

FEEL METHOD• If it makes a ball

and falls apart when you bounce it in your hand, needs irrigation

Water use

AprilM

ayJu

neJu

ly

August

September

October

Seaso

n0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0

Mean CUMax CU Min CU

Evap

otra

nspi

ratio

n (in

ches

/mon

th)

WATER MEASUREMENT

Irrigation water measurement

WEIRS

Given: Standard Contracted Rectangular Weir

L = 2 feeth = 0.40 feet

Find: Q, in cfs

Solution: Refer to Table A7-2 in BoR Water Measurement Manual, 3rd

edition

WEIRS

Water measurement

• $3 plus shipping from UW Extension

Volume

• Acre-inch: The volume of water required to cover 1 acre 1-inch deep.

• Acre-foot: The volume of water required to cover 1 acre 1-foot deep.

• 1 cubic foot = 7.48 gallons = 62.4 pounds• 1 acre-inch = 3,630 cubic feet = 27,154

gallons• 1 acre-foot = 12 acre inches = 43,560

cubic feet = 325,851 gallons

Flow

• 1 acre-inch/hour = approximately 450 gallons per minute = 1 cubic foot per second

STRATEGIES

Strategies

• Experience/observation• Gated pipe• Improving irrigation

management• Field leveling• Lining ditches

Water use efficiency

Cool season grasses

Warm season grasses

SPECIES SELECTION

Drought resistant• Orchard grass• Intermediate

wheatgrass• Other

wheatgrasses– Can tolerate only

spring water

Less resistant• Pubescent

wheatgrass• Intermediate

wheatgrass

GRAZING• Maintain

stubble at 5 to 6 inches

• Avoid irrigating while grazing

Boulder watershed study

• Study findings:– Generally, applications by

ranchers sufficient to meet the needs of the crop

Boulder watershed study

• Producer findings:– Allowed lengthened sets– Can irrigate larger area– More even distribution– Increased yields– Less labor intensive– Feel that it is more

efficient and has increased yields

Fall irrigation

Why? • Increase fall weed flush

• Can facilitate fall tillage

• Fall plant growth– Tiller production

• Leaching of salts• Storing soil

moisture

Other considerations…

• Reduced return flows?– Laramie Basin

• 74 wetlands• 65% inflows from irrigation• Most subsurface flows

– Powell, WY example

Other considerations…

Questions?

Caleb CarterUW Extension Educator Goshen County(307) 532-2436ccarte13@uwyo.edu

IRRIGATION STRATEGIES

Furrow• Less efficient• Labor intense• Soil is the conduit to

convey water as well as the absorbing surface

• Often requires a catchment and reuse area at the bottom of the field

• Water delivery schedule/amount

Surge• Can increase

efficiency• Can decrease labor• Addresses soil as the

conduit• Can help reduce runoff

if no catchment area• Can make better use

of water available

SURGE IRRIGATION

Irrigator’s equation

Qt = Ad

Q = flow ratet = timeA = area

D = depth

Irrigator’s equation

d = Qt/A

Q = Ad/t

t = Ad/Q

A = Qt/d

Irrigator’s equation

Given: d = 3 inches A = 50 acres Q = 2 cfs

Find: Time required to apply d

Irrigator’s equation

Solution: t = dA/Q

1 cfs ≈ 1 ac-in/hr

t = 75 hours

hrinac

)ac)(in(t

2

503

Irrigator’s equation

Given: t = 36 hours A = 20 acres

Q = 2 cfs

Find: Depth of applied water, d

Irrigator’s equation

Solution: d = Qt/A

1 cfs ≈ 1 ac-in/hr

d = 3.6 inches

ac

)hr)(hrinac(

d20

362