water efficiency in cool season hay production
TRANSCRIPT
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
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ly
August
September
October
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1.0
2.0
3.0
4.0
5.0
6.0
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Mean CUMax CU Min CU
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otra
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n (in
ches
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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…
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