Guide To Energy Saving And Other Benefits

Larry M. Curtis, Biosystems Engineer

Ted W. Tyson, Biosystems 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 Alabarna-grown crops in recent years. Further, micro-systems offer the potential for very significant energy savings, and thus increased profits.

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

The term "micro-inigation" 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.

Typical Micro-Irrigation System Major Conponents

 

Energy-Saving Features

Using less water at lower pressure makes micro-irrigation more energy-efficient than sprinkler irrigation. Also, micro-irrigation 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.

Further, 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 surface. Thus 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	Sprinklers
Average water pumped/day	59,863 gal	90,514 gal
System pressure	48 psi	80 psi
Energy used/day	34KWH	84KWH
Cost at $.07/KWH	$2.38/day	$5.88/day
	Micro-Irrigation savings:50 KWH/day                                           $3.50/day                                           $0.35/acre/day                                           $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 fertilizers only to plants as needed, less fertilizer (an indirect energy input) may be needed.

Other Advantages of Micro-Irrigation

The goal of any irrigation method is to promote consistently 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-irrigation also offers other particular advantages over sprinkler irrigation:

Water Sources Can Irrigate More Acres. Since micro- uses 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 water, preventing losses to deep percolation.

Terrain Problem Are Reduced. A well designed micro- system can irrigate crops onb hilly terrain where sprinkler irrigation might be impractical.

Capital Costs May Be Lower. Water amounts, pressure and flow rates are less, with more uniform application to plants (no over-watering). Thus pumps, piping and other components may be smaller and cheaper.

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- irrigation reduces the potential for fertilizer 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. 

Limitations and Potential Problems

In Alabama, micro-irrigation is best suited for high-value commercial fruit 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 extent on field crops such as cotton. The most common and serious specific problem seen in micro-irrigation 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-irrigation 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. Micro-systems 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, AW No date. Drip Irrigation Systems. Rain Bird AgriProducts Division, Glendora CA.

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

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.

Issued in furtherance of Cooperative Extension work in agriculture and home economics, Acts of May 8 and June 30, 1914, and other related acts, in cooperation with the U.S. Department of Agriculture. The Alabama Cooperative Extension System (Alabama A&M University and Auburn University) offers educational programs, materials, and equal opportunity employment to all people without regard to race, color, national origin, religion, sex, age, veteran status, or disability.

This document is author-produced (unedited).

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