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Circular ANR-644 AND ENERGY CONSERVATION

GUIDE TO ENERGY SAVINGS AND OTHER BENEFITS Larry M. Curtis, Extension Agricultural Engineer Ted W. Tyson, Extension Agricultural Engineer Steven P. Kovach, Extension Horticulturist

What Is Micro-Irrigation? To stay competitive, commercial fruit and vegetable grow­ers must maintain consistently high levels of crop quality and yield. Maintaining adequate soil moisture through irri­gation has for many producers become an important factor in achieving this goal. While overhead sprinkler systems have been the more common approach to irrigation, micro­irrigation methods have proven successful on several Ala­bama-grown crops in recent years. Further, micro- systems offer the potential for very significant energy savings, and thus increased profits.

Typical Micro-Irrigation System Major Components

- .

Sprinkler irrigation typically delivers large amounts of water to an entire field surface area whenever significant soil moisture loss has occurred, often weekly. Micro­irrigation takes a different approach in how, where and when water is applied. The micro- approach calls for:

• Delivering water directly to a plant's root zone, not wetting other soil areas; and

• Applying water at low pressure and low flow rates over longer periods and more frequently, often daily or every other day.

The term "micro-irrigation" refers to drip or trickle irriga­tion and methods using low volume micro- sprinkler or spray devices. The distinguishing feature of all micro-irriga­tion methods is that they operate at low pressure and target a portion of the plant's root zone rather than the total field area. The illustration shows the major components of a typical micro- installation.

L '\._Lateral Emitter

The Alabama Micro-Irrigation Handbook

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Energy-Saving Features Using less water at lower pressure makes micro-in·iga­

tion more energy-efficient than sprinkler irrigation. Also, micro-in·igation may offer significant energy savings when compared with non-irrigated crop management.

Compared with Sprinkler Irrigation

The energy used by an irrigation system depends on both the total amount of water pumped and the pressure needed to distribute it. Micro-irrigation systems operate at lower pressures than sprinkler systems, so micro- systems use less energy to move the same amount of water.

Futther, micro- systems are more efficient users of water than are other irrigation methods, since they apply water to plants only, not to the entire soil sutface. Tims the total amount of water pumped in a micro- system can be as little as half that of a sprinkler system, resulting in further direct energy savings. The table below compares two typical sys­tems irrigating a 10-acre orchard.

Comparison criteria Micro- system

Average water pumped/day 59,863 gal

System pressure 48 psi

Energy used/day 34KWH

Cost at $.07/KWH $2.38/day

Micro-Irrigation savings: 50 KWH/day $3.50/day

Other Advantages of Micro-Irrigation The goal of any liTigation method is to promote consis­

tently high crop quality and yield by preventing drought stress. A micro- system does a better job of this than sprin­kler methods on many crops because it maintains more constantly the moisture level plants need. Micro-liTigation also offers other particular advantages over sprinkler irriga­tion:

Water Sources Can Irrigate More Acres. Since micro­uses much less total water, the water resource becomes less of a limiting factor. In some cases, where limited water sources make sprinkler systems impractical, micro- makes irrigation possible. Also, costs of water source develop­ment (wells or impoundments) may be lower.

Soil-Related Problems Are Reduced. Since micro- sys­tems apply water at a low rate, tight clay soils are able to absorb the water without run-off or soil erosion. On sandy soils, irrigation can be scheduled in frequent, small applica­tions to match crop use and the soil's ability to hold the

Sprinklers

90,514 gal

80 psi

84KWH

$5.88/day

water, preventing losses to deep percolation.

Terrain Problems Are Reduced. A well­designed micro- system can irrigate crops on hilly terrain where sprinkler irrigation might be in1practical.

Capital Costs May Be Lower. Water amounts, pressure and flow rates are less, with more uniform application to plants

$0.35/acre/day

(no over-watering). Thus pumps, piping and other components may be smaller and cheaper. $1.40/effective acre-inch

NOTE: Comparison assumes sprinkler efficiency at 75% vs. micro- at 85%, a 75% crop factor, .25 inch/day water use, and motor and pump efficiencies (both systems) of 90% and 70%.

Compared with Non-Irrigated Management

Micro- systems may use less energy in applying fertilizer and other soil-treatment chemicals, since a portion of these can be applied through the irrigation system rather than in separate field operations.

Both direct and indirect energy inputs can be used more efficiently and effectively. If drought causes crop failure, all energy inputs up to harvest may be completely wasted. Energy savings may also be seen in normal growing sea­sons. For example, maintaining optimum soil moisture re­sults in improved plant vigor and pest-resistance. Thus, energy inputs for pest control may be lower. Also, since a micro- system can apply not only water but also fettilizers only to plants as needed, less fertilizer (an indirect energy input) may be needed.

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Input and Labor Costs May Be Lower. Since at least some chemicals can be applied through the system, overall labor costs for fertilizer application may be reduced. And, when fertilizers or other chemicals are ap­plied through the micro- system, amounts needed-and costs-may be lower.

Water Quality Is Protected. By applying fertilizers on an as-needed basis, micro- inigation reduces the potential for fettilizer leaching into aquifers or running off into lakes or streams.

Pest Problems May Be Reduced. Sprinklers water both crop and weeds. Micro- systems help to control weeds by not wetting between-plant and between-row areas. Disease problems may be reduced because plant leaves are not wetted by the irrigation system.

Field Operations Are Easier. Since only the plant root zone is wetted, workers have access to fields on firm foot­ing at any time, and field operations can go on at the same time as irrigation.

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Limitations and Potential Problems In Alabama, micro-inigation is best suited for high-value

commercial fmit and vegetable crops where consistent yields of a high quality product are essential for long-term success. Micro- is not suited to closely planted crops such as small grains, and has been used only to a limited e"A'tent on field crops such as cotton. The most common and seri­ous specific problem seen in micro-inigation is clogging. Clogging usually becomes a problem only if water quality factors are neglected in the system design or if the system is not properly monitored and maintained. Overall, micro­systems require more careful design and installation and a higher and more constant level of management supervision than do sprinkler systems.

Clogging. Small amounts of sand, silt or organic matter can rapidly clog lines and emitters. For consistently suc­cessful operation, a micro-inigation system must draw from a good quality water source, have adequate filtration, and be properly maintained. Filters should usually include fine-mesh screen and sand/gravel media. Maintenance requirements include regular back-flushing and other cleaning of filters, and injection of chlorine or other chemi­cals to prevent clogging by iron oxides, calcium carbonate, algae or bacterial slimes. In operation, emitters should be monitored at least once a week for proper performance.

Concentration of Water in Plant Root Zone. Micro­systems apply water to a small area, usually 25 to 60 per­cent of the plant's root zone. Systems must therefore be de­signed with close attention to the soil type and structure, to make sure the water spreads to the intended area. Also, since plants may concentrate their roots in the wetted area, a break-down in the system may cause rapid plant stress. Thus the grower must monitor the system carefully.

Possible System Damage by Pests. Insects and animals, especially rodents, occasionally damage micro-inigation lines. Pest control methods may be necessary. Burying irri­gation lines is a desirable preventive step.

References Boswell, M.J. 1990. Micro-Irrigation Design Manual. James Hardie Irrigation Co., El Cajon CA.

Clark, G.A., et al. 1991. Micro-Irrigation in Mulched Bed Systems: Components, System Capacities and Management. Bulletin 245, Florida Cooperative Extension Service, University of Florida.

Fereres, E., ed. 1981 . Drip Irrigation Management. Leaflet 21259, Division of Agricultural Sciences, University of California.

Fry, A.W. No date. Drip Irrigation Systems. Rain Bird Agri­Products Division, Glendora CA.

Key Questions to Ask in Considering Micro-Irrigation

It you are considering a micro-irrigation system, here are the basic questions you should ask. These are not all easy questions with clear-cut answers. But all are answerable, given the right information. This handbook provides basic infor­mation to help you make a sound decision. For more information or advice on your particular situation, call your County Extension Agent.

0 Do I have an adequate water source, or can I develop a water source at economical cost?

0 Is my water quality adequate, so that filtration and treatment will be cost-effective?

0 Is the crop I am considering irrigat­ing suited for micro-irrigation?

0 Am I willing and able to exercise the needed level of management supervision?

0 Will the crop I plan to irrigate gener­ate enough income to pay the cost of the system and all other inputs and return a profit?

Publications included in the Alabama Micro-Irrigation Handbook present up-to-date information on practical irrigation methods that save energy and water while protecting water quality. For more information, see your county Extension agent.

Lyons, C.G., ed. No date. Texas Peach Handbook. Texas Agricultural Extension Service, Texas Agricultural Experiment Station, College of Agriculture, Texas A & M University System.

Ross, D.S., et al. 1980. Trickle Irrigation in the Eastern United States. Circular NRAES-4, Northeast Regional Agricultural Engineering Service, Cornell University.

Sneed, R.E. and R.O. Evans. 1991 . Selection and Management of Efficient Low Volume Irrigation Systems. EBAE-91-153, North Carolina Cooperative Extension Service.

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Layout of a Basic Micro-Irrigation System (Emitters not shown; types commonly used are illustrated below.)

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Zone 1

Air relief & Air relief & flush valve

flush valve w....;.....;.....;.....;.....;.....,.....;....,; ______ '"-(XJ

~gauge

Main line

Zone 2

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Manifold

\L' Laterals

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Control valve & pressure regulator

Line source emitter (drip tape) on row crops Micro- spray emitter on trees Typical wetting action

Drip emitter on trees

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E1.A.~A iabama iil7Coo pe ra tive

Extension Service AUBURN UNIVERSITY

Micro- sprinkler on trees Typical wetting action

Illustration adapted from M.J. Boswell, Micro-Irrigation Design Manual.

This material was prepared with the support of the U.S. Department of Energy (DOE) Grant No. DE-FG-44-BOR410074, through the Science, Technology and Energy Division of the Alabama Department of Economic and Community Affairs. However, any opinions, findings, conclusions or recommendations expressed herein are those of the authors and do not necessarily reflect the view of DOE. Issued in furtherance of Cooperative Extension work in agriculture and home economics, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture. The Alabama Cooperative Extension Service, Auburn University, Ann E. Thompson, Director, offers educational programs and materials to all people without regard to race, color, national origin, sex, age, or handicap and is an equal opportunity employer. UPS, 1.2M17, 6:92, ANR-644

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