Marshall J. English
Robert Mittelstadt
This is a brief summary of management practices for irrigated agriculture. Its purpose is to help irrigated agriculture in its effort to protect ground and surface water supplies in Oregon. Both point sources and nonpoint sources contribute to water contamination. It is focused on best management practices, supported by a catalog of relevant reference publications to which the reader can turn for more detailed information.
This publication is derived - much of it verbatim - from an earlier publication by Hermanson and Canessa (1995) which has funded by the Washington Department of Ecology. Their excellent work has been adapted for Oregon in several ways: (i) by adding material derived from research and field experience in Oregon and other states, (ii) by supplementing the lists of references with others which complement the original list, and (iii) by modifying those sections which deal with statutes peculiar to the individual states.
In irrigated agriculture, important point sources are agri-chemical spills or leaks and the back-siphoning of agri-chemicals into the well due to improperly implemented chemigation equipment. Important non-point sources include the leaching of nutrients and/or pesticides from the crop root zone and surface runoff. State and Federal agencies emphasize voluntary adoption of practices that will reduce and prevent nonpoint source pollution. This publication is not a regulatory document. However, some practices contained herein are regulated by State law (ie. chemigation).
Six management objectives are presented along with corresponding farm practices designed to meet each objective. The six overall management objectives are as follows:
1.00 Minimize water losses in the on-farm distribution system
2.00 Improve irrigation system performance and management
3.00 Manage fertilizer program to minimize excess fertilizer available for leaching and runoff
4.00 Manage crop protection program to minimize leaching and runoff of chemical residues
5.00 Reduce contamination of surface waters by sedimentation
6.00 Prevent aquifer contamination at wellhead
Accompanying each practice, pertinent standards, engineering practices, extension publications, rules and statutes and other references are cited where applicable. These references will aid the user in evaluating and implementing a specific practice. As noted, a number of useful irrigation related publications have been made available by Oregon State University, Washington State University and University of Idaho Cooperative Extension. These can be obtained from your OSU Extension agent or by contacting Agricultural Communications at Oregon State University.
Before considering the adoption of any practices in this publication, it would be prudent to first consider an overall management goal for the farm. For example, an overall management goal could be to improve on-farm water application efficiency for periods of drought. In this case, most of the management objectives listed above would be applicable. Some management practices will complement others and some may not. Lastly, some of the management practices suggested will require on-farm experimentation and/or several years of experience to satisfactorily implement.
Of fundamental importance to proper irrigation water management and overall farm management are proper design and calibration of equipment, equipment maintenance and careful recordkeeping of all applications.
The on-farm distribution system moves water from the primary supply (well, canal or river) to the field(s). Depending on configuration, the on-farm distribution system may cause erosion of unlined ditches and deep percolation from seepage.
1.1 Install concrete slip-form ditches to replace earthen ditches. (SCS National Practice 320, 430A; ASAE Std. S289.1)
1.2 Convert earthen ditches to piplines or gated pipe. (SCS National Practices 430-AA through HH; ASAE Stds. S376.1, S261.6)
1.3 Install flexible membrane linings in earthen ditches and/or reservoirs. (SCS National Practice 428B, 521A; ASAE Std. EP340.2)
1.4 Install swelling clays or other engineered material in earthen ditches and/or reservoirs. (SCS National Practices 521B through E)
1.5 Maintain ditches and pipelines to prevent leaks. (PNW 293; SCS National Practice 587)
Efficient irrigation makes the best use of available water while minimizing the negative effects on water quality from deep percolation and surface runoff. Good irrigation system performance is the result of a carefully considered system design, prudent equipment maintenance and proper irrigation water management. Knowing when and how much to irrigate is important for effective management. This can be accomplished through irrigation scheduling (see Appendix A).
General recommendations for all system types
2.1 Measure all water applications accurately. (EC1369; Installation and use of Powlus v-notch flumes, ARS Kimberly, ID; Irrigation Journal, Sept./Oct. 1995; SCS National Engineering Handbook: Section 15, Chapter 5 for siphon tubes)
2.2 Monitor pumping plant efficiency. Consult local utility regarding energy audit programs. (PNW 285 and PNW 293; A303-Energy Note; Irrigation Journal, July/Aug. 1995)
2.3 Regularly evaluate the irrigation system using standardized procedures. (ASAE Stds. S298.1 for sprinkler testing, EP419 for furrow systems, S436 for center-pivots; local NRCS or SWCD office; see also PNW 293)
2.4 Evaluate water quality and soil chemistry to determine required annual leaching ratios to maintain salt balances in the root zone. (EC 628; FG 76; SCS National Practice 610)
2.5 Use irrigation scheduling as an aid to decide when and how much to irrigate. (see Appendix A)
2.6 Consider changing type of irrigation system to improve irrigation performance. (contact local SCS/SWCD office and/or local irrigation dealership)
2.7 Use aerial photography (either conventional or, preferably, infrared photography) to help identify irrigation and/or drainage problems (Baber, 1982).
2.8 Properly design, construct and maintain subsurface drainage systems to manage water table, if applicable. (ASAE Stds. EP463, 479).
Practices for surface irrigation (furrow/rill/border)
2.9 Improve uniformity by increasing furrow flows to maximum non-erosive streamsize during advance.
2.10 Employ surge-flow techniques (WSU drought advisory EM4826; OSU AES Special Reports 924, 936, 947; Irrigation Journal, March 1995; WRRP W- 163, Utah State University; ASAE Std. EP419)
2.11 Improve uniformity by decreasing length of furrow runs. This may be accomplished by extending gated pipe to the center of the field.
2.12 For improved uniformity, install a suitable field gradient using laser- controlled land grading. (SCS National Practice 464, 466)
2.13 To equalize furrow infiltration rates, drive a tractor in the uncompacted furrows to intentionally form all "wheel traffic" furrows.
2.14 Rip hardpans and compacted soil layers to improve infiltration rates. (SCS National Practice 324)
2.15 After advance, "cutback" or reduce furrow inflow rates to reduce runoff while ensuring good uniformity.
2.16 Install runoff-reuse or "tailwater" recovery systems. (ASAE Stds. EP408.1, 369.1; SCS National Practice 447)
2.17 Practice alternate or alternating furrow irrigation. (OSU AES Special Reports 924, 936)
Practices for sprinkle irrigation systems
2.18 Have an irrigation engineer or specialist check hand-line and side-roll field layouts to ensure correct combinations of spacing, operating pressure, sprinkler head and nozzle size/type to ensure proper overlap of sprinkler patterns. Use a lateral offset technique if practical. (PNW 286; Irrigation Journal, Nov./Dec. 1995)
2.19 Have an irrigation engineer or specialist check field layouts for flow uniformity between sprinklers. Use flow control nozzles and pressure regulators as necessary.
2.20 Maintain sprinkle systems in good operating condition. (PNW 293; OSU Irrigators Pocket Guide)
2.21 Operate in low-wind conditions if possible to avoid excessive drift and evaporative losses.
2.22 Ensure that sprinkler packages match the infiltration rate of the soil, especially at the outside edges of a center-pivot. (PNW 287, 360; SCS National Engineering Handbook: Section 15, Chapter 2; Irrigation Journal, Nov./Dec. 1995)
2.23 Test sprinklers for performance using standardized procedures. Test information should be available from dealer or manufacturer. (ASAE Stds. S330.1, S398.1).
2.24 Minimize surface runoff from sprinkle irrigated fields. Use reservoir tillage techniques (dammer/diker), conservation tillage techniques and manage agricultural residues. (PNW 287)
2.25 For container nurseries, install runoff-reuse or zero runoff systems. Zero discharge is required by ODEQ during the irrigation season, between May 1 and October 1. (Oregon Container Nursery Irrigation Water Management Plan, 1991).
Practices for micro-irrigation systems
2.26 Have an irrigation engineer or specialist check the design for pressure uniformity. Use pressure/flow regulators and pressure compensating emitters as necessary. (ASAE Stds. EP405.1, EP458)
2.27 Have irrigation water analyzed to properly design water treatment and filtration system. (contact irrigation dealership; Irrigation Journal, April 1995; see also 3.5)
2.28 Test combinations of irrigation water/fertilizer/other additives in the system to ensure compatibility. (see also 3.5)
2.29 Practice regular maintenance to ensure designed system performance. (ASAE Stds. EP405.1, EP458)
A well planned and managed fertilizer program is essential to produce crops economically and with minimal contamination to ground and surface water supplies. The nutrients of primary concern are nitrate-nitrogen and phosphorus. Nitrate-nitrogen is susceptible to leaching with deep percolation. In contrast, phosporus tends to adsorb to soil particles and may be lost to surface water bodies when erosion and runoff occur.
Fertigation is the practice of applying nutrients by injecting them directly into the stream of irrigation water. It is an effective and convenient method for applying nutrients. Oregon Administrative Rule OAR 690-215-017 covers the requirements for chemigation/fertigation equipment.
Overall good practices for fertilizer management
3.1 Assess the risk of contamination of ground and surface waters. (EM 8559, EM 8561)
3.2 Consider cropping patterns that include deep-rooted crops to scavenge residual fertilizer. Small grains, corn and sugar beets are three deep rooted crops that might be considered. (Follett, et al. 1991)
3.3 Maintain records of all tissue tests, fertilizer tests, cropping rotations, yields and applications.
3.4 Employ a nutrient "budget" to balance crop needs with fertilizer applications. See 3.5 through 3.7.
3.5 Analyze fields for residual nutrients prior to planting, (EC 628), occasionally sampling to deeper depths (e.g. 4' to 6') to determine level of nitrogen below the 2' level. Then reduce additional nitrogen applied for deeper rooted crops (see 3.2).
3.6 Analyze irrigation water for nitrogen content, (FG 76; OSU AES Special Report 924), and if the water contains nitrogen, reduce the amount of additional nitrogen applied proportionately.
3.7 Analyze plant tissue to identify fertilizer requirements during the growing season.
3.8 Always calibrate application equipment including manure spreaders, to uniformly apply the planned amount.
3.9 Develop realistic yield goals and maintain yield records.
3.10 Schedule fertilizer applications to avoid periods when irrigation is being done for purposes of leaching, plant cooling or frost control.
3.11 Use nitrification inhibitors in combination with applications of ammoniacal forms. Nitrate-nitrogen is most susceptible to leaching losses.
3.12 Use slow-release nitrogen fertilizers.
3.13 Incorporate surface applied fertilizers immediately to reduce volatilization. This is particularly important for urea and ammonium based nitrogen fertilizers applied to alkaline soils. Also important for manure.
3.14 On sandy, porous soils subject to rapid leaching, avoid applying large amounts of nitrogen pre-plant or early-season whenever possible. Apply smaller increments as needed during the growing seasons.
Special considerations for manure applications
3.15 Test manure or other waste materials for nutrient content, (PNW 239; EM8586; EC1094; WSU EB1719), and reduce additional nutrients applied accordingly.
3.16 Do not apply manure to frozen ground, especially on sloping fields.
Special considerations for fertigation (application of fertilizers with irrigation)
3.17 Analyze irrigation water for compatibility with fertilizer to be applied. Ammonia injection causes a rise in pH and possible precipitation of soluble calcium and magnesium which may coat the inside of pipes and plug emitters. For phosphorus fertilizers, if the water contains appreciable amounts of calcium, any form of phosphorus will precipitate in pipelines and emitters (Nakayama, F.S, 1982).
3.18 Use fertigation properly and in accordance with state regulations. In Oregon, OAR 690-215-017 covers requirements for fertigation/chemigation equipment. (ASAE Std. EP409.1; PNW 360)
3.19 Design and maintain irrigation system for good application uniformity. See also 2.18 and 2.19. (ASAE Stds. S298.1 for sprinkler testing, EP419 for furrow systems, S346 for center-pivots; local NRCS/SWCD office; OSU Irrigator's Pocket Guide; see also PNW 293)
The primary factors that affect the agri-chemical's fate are the pesticide properties (adsorptivity, degradation rate, solubility and volatility), soil properties, site conditions and application practices. Applied pesticides may evaporate, be carried off the field attached to soil particles or in solution, be broken down into other substances, or be taken up by plants or insects as intended. The definition of "pesticide residue" may be found in Oregon Administrative Rule (OAR) 340-109.
Effective crop protection while limiting chemical leaching and/or runoff requires a management program. A major practice cited below is Integrated Pest Management (IPM) or Integrated Crop Management (ICM). These refer to a collection of management practices that reduces the overall dependency upon synthetic chemicals and increases the effectiveness of those that are used. This encompasses such practices as crop rotation, effective scouting for pests and disease, use of natural bio-controls, soil tillage and conditioning, and irrigation management. Of particular importance to irrigated agriculture is chemigation. Chemigation is the practice of applying chemicals by injecting them directly into the irrigation water. There are special Federal and State requirements concerning the proper implementation of chemigation equipment. The EPA and Sate of Oregon require all pesticide applicators to be registered (EPA 40 CFR Part 171; OAR 603-57).
Overall good practices
4.1 Assess the risk of contamination of ground and surface water supplies. (EM8559; EM8561).
4.2 Practice Integrated Pest Management techniques where applicable. (contact OSU Extension Agent)
4.3 Schedule applications for maximum effectiveness.
4.4 Maintain good records of all chemicals purchased, applied and in storage as well as field surveys for pest populations (Federal Pesticide Recordkeeping Requirements, 1993; OSU Extension Service Pesticide Application Record).
4.5 Read and follow all label instructions. (EM8532)
4.6 Transport and store chemicals properly. (EM8532)
4.7 Load and mix pesticides properly. Record concentrations and rates of individual applications. (EM8532)
4.8 Store and dispose of used containers properly. (The OACFA sponsors a pesticide container recycling program in Oregon, contact your dealer or Oregon Agricultural Chemicals and Fertilizers Association)
4.9 Maintain equipment properly to reduce spills or leaks.
4.10 Clean equipment properly after use. (EM8532; Factsheet: Oregon Waste Reduction Assistance Program, ODEQ; PNW 360 for chemigation)
4.11 Calibrate application equipment. (PNW 360 for chemigation)
Special considerations for chemigation
4.12 Analyze irrigation water for compatibility with chemicals to be applied by chemigation.
4.13 Use chemigation safely and according to regulations. (PNW 360; ASAE Std. EP409.1; OAR 690-215-017)
Surface soil movement from irrigation, wind, or rainfall creates the potential for contamination by sedimentation. Sediment is itself a contaminant, and can also carry adsorbed chemicals to surface water. It is therefore important to minimize erosion and surface movement (note that practices which reduce movement may increase deep percolation and leaching).
Methods to reduce in-field erosion
5.1 Use cover crops on unprotected, soils that are easily eroded by wind or water.
5.2 Manage crop residues and/or soil stabilizing crops to increase surface roughness and infiltration, and to decrease surface movement by wind erosion. (SCS-CRN-02, 1992).
5.3 Install straw mulch in row-crop furrows. This practice is of particular importance for furrow irrigation of easily erodible soils. (OSU AES Special Reports 922, 924, 936, 947; SCS National Practice 484)
5.4 Use reduced tillage, such as paraplow systems. (SCS National Practice 329)
5.5 Grade the land to optimize field slopes for improved irrigation uniformity and reduced runoff with furrow irrigation systems. (SCS National Practice 464, 466)
5.6 Install tail-water drop structures to dissipate erosive energy in steeply sloping terrain. (SCS National Practice 410)
5.7 Install buried tailwater drops and collection pipes.
5.8 Properly design, install and maintain surface drainage systems. (ASAE Stds. EP302, EP407)
5.9 Treat irrigation water with polyacrylamide (PAM) for furrow irrigation systems. (OSU AES Special Report 947)
Practices to treat sediment-laden runoff water
5.10 Install sedimentation basins. (SCS National Practice 350; ASAE Std. S442)
5.11 Install vegetative buffering (filter) strips. (SCS National Practice 393)
5.12 Collect and reuse surface runoff. (ASAE Stds. EP408.1, 369.1; SCS National Practice 447; USDA ARS, Kimberly, ID)
Wells are a direct link from the surface to ground water. Aquifer contamination can occur because of movement of nutrients or other chemicals from the surface through or along the well. Activities near the wellhead may introduce contaminants to the well and those activities should therefore be identified and curtailed.
The 1986 amendment to the federal Clean Water Act (CWA) requires each state to develop guidelines for wellhead protection for public water supplies. A wellhead protection area is defined as: "The surface and subsurface area surrounding a water well or wellfield supplying a public water system through which contaminants are likely to move toward and reach such water well or wellfield." The Oregon Dept. of Environmental Quality (ODEQ) is the lead agency for this program and is responsible for developing educational as well as technical guidelines (Oregon Wellhead Protection Program Guidance Manual, Review Draft, November 1995; EPA Seminar Publication, Wellhead Protection: A Guide for Small Communities, 1993).
Abandoned wells must be properly filled and capped so there is no path from the surface to the aquifer. The Oregon Dept. of Water Resources (OWRD) is responsible for developing well construction, maintenance and abandonment requirements. Well construction and abandonment are generally covered by Oregon State law (ORS 537.505, 537.772, 537.775) and administrative rule (OAR 690).
Special considerations for well construction and maintenance
6.1 Properly design and construct irrigation wells. (ASAE Std. EP400.1)
6.2 Construct wells properly where there is the possibility of cascading flows contaminating a lower aquifer.
6.3 Identify and properly seal all abandoned and improperly constructed wells. (ORS 537.772, 537.775; WSU EB1714)
6.4 Prevent back siphonage/flow of chemicals or nutrients down a well during or after chemigation. (PNW 360; ASAE Std. EP409.1; OAR 690-215-017)
6.5 Do not store, load, or mix chemicals near a wellhead or other vulnerable place. (EPA/625/R-93/002)
Improved irrigation system hardware and management may result in greater distribution uniformity and improve the potential for higher application efficiency. It follows that distribution uniformity is the first concern when improving irrigation system performance. However, achieving high application efficiency ultimately depends on the management of the system, that is, knowing when and how much to irrigate. Irrigation scheduling techniques greatly enhance the irrigator's ability to manage water applications. Furthermore, it is necessary to properly maintain irrigation equipment so that system performance is dependable and predictable.
Proper management of fertilizers and agri-chemicals will limit their availability for leaching or runoff losses possibly contaminating ground and surface water supplies. Maintaining and calibrating all application equipment and careful record keeping are the principle components to a good management program. The application of fertilizers and pesticides through irrigation water (chemigation) can be an effective and efficient mode of application. There are, however, federal and state requirements when implementing chemigation equipment which must be met. Cultural practices must also be considered as to their role in irrigation performance, nutrient and pesticide management, and soil erosion (especially on sloped fields, and on fields susceptible to wind erosion).
Groundwater contamination may also occur at or near a wellhead. Chemicals
should not be stored, loaded or mixed near a wellhead. In addition, wells should be properly constructed, maintained and abandoned as required by the State Water Resources Department of Oregon.
The primary purpose of this document is to present six management objectives for irrigated farms and to briefly list appropriate implementation practices for each objective. These management objectives aim to help irrigated agriculture in its effort to protect groundwater and surface water supplies from point and non-point source pollution while maintaining farm productivity.
American Society of Agricultural Engineers, ASAE Standards, 42st ed. 1995.
Baber, J.A. Detecting Crop Conditions with Low-Altitude Aerial Photography. In: Remote Sensing for Resource Management. Soil Conservation Society of America. 1982.
Brown, L., Booher, L., Irrigation on Steep Land, California Agricultural Experiment Station and Extension Service, Circular 561, 1972.
Canessa, P., Hermanson, R., Irrigation Management Practices to Protect Groundwater and Surface Water Quality, State of Washington. Washington State University Cooperative Extension publication EM 4885, 1995.
Cuenca, R., Nuss, J., Martinez-Cob, A., Katul, G., MªFaci González, J., Oregon Crop Water Use and Irrigation Requirements, Oregon State University Extension publication EM 8530, 1992.
Federal Pesticide Recordkeeping Requirements. 1993. Anonymous.
Feibert, E., Shock, C., Saunders, M., A Preliminary Investigation of the Optimum Soil Water Potential for Quality Onion Production, Oregon State University Malheur Agricultural Experiment Station Special Report 924, 1993.
Feibert, E., Shock, C., Saunders, M., A Preliminary Comparison of Sprinkler, Subsurface Drip and Furrow Irrigation of Onions, Oregon State University Malheur Agricultural Experiment Station Special Report 924, 1993.
Feibert, E., Shock, C., Saunders, M., A Comparison of Sprinkler, Subsurface Drip and Furrow Irrigation of Onions, Oregon State University Malheur Agricultural Experiment Station Special Report 947, 1995.
Feibert, E., Shock, C., Saunders, M., Appropriate Nitrogen Fertilization for Potato Varieties Grown in the Treasure Valley, Oregon State University Malheur Agricultural Experiment Station Special Report 924, 1993.
Feibert, E., Shock, C., Saunders, M., Nitrogen Fertilization for Potato Varieties Grown Under Sprinkler Irrigation, 1994 Trial, Oregon State University Malheur Agricultural Experiment Station Special Report 947, 1995.
Follett, R.F. D.R. Keeney, and R.M. Cruse. Managing Nitrogen for Goundwater Quality and Farm Profitability. Soil Science Society of America, Inc., Madison, WI, 1991.
Gardner, H., Hart, J., How to Take a Soil Sample...and Why, Oregon State University Extension publication EC 628, 1995.
Hansen, Hugh, J., and Trimmer, Walter L., Irrigation Runoff Control Strategies, Pacific Northwest Extension publication PNW 287 (Oregon State University, 1986).
Hansen, Hugh J., and Trimmer, Walter L., Irrigation System Walk-Through Inspection Analysis, Pacific Northwest Publication PNW 293 (Oregon State University, 1986).
Hansen, Hugh J., and Trimmer, Walter L., Converting Sprinkler Systems to Lower Pressure, Pacific Northwest Extension publication PNW 289 (Oregon State University, 1986).
Hansen, Hugh J., and Trimmer, Walter L., Pumping Plant Efficiencies, Pacific Northwest Publication PNW 285 (Oregon State University, 1986).
Hermanson, R.E., Kalita, P.K., Animal Manure Data Sheet, Washington State University Cooperative Extension EB1719, 1994.
Huddleston, J., How Soil Properties Affect Groundwater Vulnerability to Pesticide Contamination, Oregon State University Extension publication EM 8559, 1994.
Keller, J., Bliesner, R., Sprinkle and Trickle Irrigation, Chapman and Hall, 1990.
Kengla, S., Huddelston, J., Putting Sludge to Good Use, Oregon State University Extension publication EC 1410, 1994.
Kerle, E., Jenkins, J., Vogue, P., Understanding Pesticide Persistance and Mobility for Groundwater and Surface Water Protection, Oregon State University Extension publication EM 8561, 1994.
Lenhart, N., Sward, M., The State of Water in Oregon, Oregon State University Extension publication EC 1426, 1993.
Ley, T., Stevens, R., Topielec, R., Neibling, W., Soil Water Monitoring and Measurement, Pacific Northwest Publication, PNW 475 (Oregon State University, 1994).
Ley, T. Simple Irrigation Scheduling Using Pan Evaporation, Washington State University Cooperative Extension publication EB 1304, 1984.
Miller, J., Shock, C., The Effect of Surge Irrigation on Onion Yield and Quality, Irrigation Efficiency, and Soil Nitrogen Losses, Oregon State University Malheur Agricultural Experiment Station Special Report 924, 1993.
Miller, J., Shock, C., Saunders, M., Efficiency of Nitrogen Fertilization on Onions, Oregon State University Malheur Agricultural Experiment Station Special Report 924, 1993.
Montana Department of Natural Resources and Conservation, Irrigator's Pocket Guide, Oregon State University Energy Extension, undated.
Nakayama, F.S., Water Analysis and Treatment Techniques to Control Emitter Plugging. Water, Energy and Economic Alternatives, pp. 97-112, 1982 Annual Technical Conference Proceedings, Feb. 21-24, Portland, OR, The Irrigation Association.
Stewart, S., Nelson, D., Oregon Wellhead Protection Program Guidance Manual, Oregon Department of Environmental Quality and Oregon Health Division, Review Draft, 1995.
Oregon Container Nursery Irrigation Water Management Plan. Anonymous, 1991.
Oregon Department of Energy, Oregon Business Energy Tax Credit (BETC), Application for Preliminary Certification - Conservation Projects, 1993.
Oregon Department of Environmental Quality, Oregon Waste Reduction Assistance Program, Factsheet, 1993.
Oregon Department of Environmental Quality, Groundwater Management and Protection Strategy: Oregon Plan, July 19883.
Oregon Department of Environmental Quality, Oregon's 1994 Water Quality Status Assessment Report, 305(b) Report, April, 1994.
Oregon State University Extension Service and Agricultural Experiment Station, Educational Materials, EM 8289, July, 1995.
Oregon State University Extension Service. Pesticide Application Record. Terry Miller. 1993.
Oregon Water Resources Department, 1993 Oregon Water Laws, Volume 1, 1993.
Oregon Water Resources Department, 1993 Oregon Water Laws, Volume 1I, 1993.
Parsons, D., Witt, J., Pesticides in Groundwater in the United States of America, Oregon State University Extension publication EM 8406, 1989.
Shock, C., Hobson, J., Banner, J., Saunders, L., Stieber, T., An Evaluation of Mechanically Applied Straw Mulch on Furrow Irrigated Onions, Oregon State University Malheur Agricultural Experiment Station Special Report 924, 1993.
Shock, C., Feibert, E., Saunders, M., Appropriate Irrigation Management for Potato Varieties; Variety Tolerance to Deficit Irrigation, Oregon State University Malheur Agricultural Experiment Station Special Report 924, 1993.
Shock, C., Stieber, T., Eldredge, E., A Comparison of Drip, Sprinkler, and Furrow Irrigation of Potatoes, Oregon State University Malheur Agricultural Experiment Station Special Report 924, 1993.
Shock, C., Hobson, J., Banner, J., Saunders, L., Townley, B., Improved Irrigation Efficiency and Erosion Protection by Mechanical Furrow Mulching Sugarbeets, Oregon State University Malheur Agricultural Experiment Station Special Report 924, 1993.
Shock, C., Stieber, T., Miller, J., Nutrient Content in Northeastern Malheur County Irrigation Water, Oregon State University Malheur Agricultural Experiment Station Special Report 924, 1993.
Shock, C., Feibert, E., Saunders, M., Soil Water Potential Criteria for Onion Irrigation, 1994 Trial, Oregon State University Malheur Agricultural Experiment Station Special Report 947, 1995.
Shock, C., Feibert, E., Saunders, L., Irrigation Management for Potato Varieties; Variety Tolerance to Deficit Irrigation, Oregon State University Malheur Agricultural Experiment Station Special Report 947, 1995.
Shock, C., Zattiero, J., Kantola, K. Saunders, M., Comparative Cost and Effectiveness of Polyacrylamide and Straw Mulch on Sediment Loss from Furrow Irrigated Potatoes, Oregon State University Malheur Agricultural Experiment Station Special Report 947, 1993.
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Topielec, R., Measuring Crop Water Use and Available Soil Moisture, Energy Note, Oregon State University Energy Extension publication A306, 1993.
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Trimmer, Walter L., Ley, Thomas W., Clough, George, Larsen, Dorrell, Chemigation in the Pacific Northwest, Pacific Northwest Extension publication PNW 360 (Oregon State University, 1992).
Trimmer, Walter L., Measuring Well Water Levels, Oregon State University Extension publication EC 1368, 1994.
Trimmer, Walter L., Hansen, Hugh J., Offsets for Stationary Sprinkler Systems, Pacific Northwest Extension publication PNW 286 (Oregon State University, 1986).
Trimmer, Walter L., Hansen, Hugh J., Electrical Demand Charges - How to Keep them Low, Pacific Northwest Extension publication PNW 291 (Oregon State University, 1986).
Trimmer, Walter L., Hansen, Hugh J., Extending Electrical Motor Life, Pacific Northwest Extension publication PNW 292 (Oregon State University, 1986).
Trimmer, Walter L., Hansen, Hugh J., Sizing Irrigation Mainlines and Fittings, Pacific Northwest Extension publication PNW 290, 1986.
Trimmer, Walter L., Stretching Irrigation Water Supplies, Pacific Northwest publication PNW 323 (Oregon State University, 1994).
Trimmer, Walter L., Hansen, Hugh J., Irrigation Scheduling, Pacific Northwest Extension publication PNW 288 (Oregon State University, ,1994).
Trimmer, Walter L., Estimating Water Flow Rates, Oregon State University Extension publication EC 1369, 1994.
Trout, T., Installation and Use of Powlus V-notch Flumes, U.S. Agricultural Research Service, Kimberly, ID, undated.
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Wright, R., Maintaining Impact Sprinklers, Energy Notes, Oregon State University Energy Extension publication A304 (Oregon State University, 1986).
Wright, R., Checking Electic Motor Load, Energy Notes, Oregon State University Energy Extension publication A305 (Oregon State University, 1986).
Cross-reference listing of publications
Cooperative Extension Publications (Oregon, Washington, Idaho)
PNW 285 Pumping Plant Efficiencies
PNW 286 Offsets for Stationary Sprinkler Systems
PNW 287 Irrigation Runoff Control Strategies
PNW 288 Irrigation Scheduling
PNW 289 Converting Sprinkler Systems to Lower Pressure
PNW 291 Electrical Demand Charges - How to Keep them Low
PNW 292 Extending Electrical Motor Life
PNW 293 Irrigation System Walk-Through Inspection Analysis
PNW 323 Stretching Irrigation Water Supplies
PNW 360 Chemigation in the Pacific Northwest
PNW 475 Soil Water Monitoring and Measurement
Oregon State University Extension Publications (in addition to the above)
FG 74 A List of Analytical Laboratories Serving Oregon
FG 76 Irrigation Water Quality
FS 281 Manure Management Practices to Reduce Water Pollution
EC 628 How to Take a Soil Sample and Why
EC 1368 Measuring Well Water Levels
EC 1369 Estimating Water Flow Rates
EC 1374 Rural Domestic Water Supply
EC 1426 The State of Water in Oregon
EM 8530 Oregon Crop Water Use and Irrigation Requirements
EM 8546 Home-A-Syst Homestead Assessment System (a set of 20 publications dealing with protecting the groundwater that supplies drinking water)
EM 8532 Oregon Pesticide Applicator Manual (available in Spanish)
EM 8559 How Soil Properties Affect Groundwater Vulnerability to Pesticide Contamination
EM 8560 Site Assessment for Groundwater Vulnerability to Pesticide Contamination
EM 8561 Understanding Pesticide Persistence and Mobility for Groundwater and Surface Water Protectiong
Oregon State University Energy Extension Notes (contact Energy Extension)
A303 Irrigation Pump Efficiency Test
A304 Maintaining Impact Sprinklers
A305 Checking Electric Motor Load
A306 Measuring Crop Water Use and Available Soil Moisture
Oregon Irrigator's Pocket Guide
An irrigation scheduling program consists of four elements: (1) agronomic knowledge of the soils and crop, (2) a method of measuring soil moisture status, (3) a means of measuring or estimating daily crop water use and (4) an estimate of the application efficiency of your irrigation system. With this information, a water balance (or budget) may be established for a given field and the irrigator will be able to apply the correct amount of water at the right time.
The soil and crop information required are: soil water holding capacity, mature crop rooting depth or root zone depth, and allowable depletion (the percent of water stored in the root zone which is allowed to deplete before an irrigation is required). This information may be determined from field experience and/or obtained from other sources including but not limited to PNW 288 and 475, OSU Energy Extension Energy Note A306, OSU Irrigator's Pocket Guide, SCS Engineering Handbook (Section 15, Chapter 2), WSU EB 1304 or your OSU Extension Agent.
An accurate yet economical means of measuring soil moisture in the crop root zone is essential. To help irrigator's decide on the appropriate equipment, a recent Pacific Northwest Extension publication, PNW 475, reviews and compares several tools for measuring and monitoring soil moisture.
There are several means by which daily crop water use (evapotranspiration or ET) can be estimated or measured. For evaporation measurement on the farm, a standardized evaporation pan is used and daily evaporation is related to crop ET by the crop coefficient (WSU EB 1304). Secondly, weather data may be used to calculate daily crop ET by the Modified Penman or Blainey-Criddle methods (James, 1988; Cuenca, 1989). An OSU Extension publication, EM 8530, published in 1992, provides monthly estimates of crop water use and irrigation requirements in Oregon for each region and crop. These estimates were calculated using the Modified Blaney-Criddle method along with weather data compiled from 244 existing National Weather Service Stations in Oregon. In addition, several automatic weather stations have been installed throughout Oregon by the U.S. Bureau of Reclamation and Bonneville Power Administration which collect weather data and transmit the data via satellite to Boise, Idaho, where daily ET is calculated for all important regional crops. This system is known as Agrimet and current Oregon Agrimet station locations include: Forest Grove, Corvallis, Bandon, Medford, Madras, Hood River, Christmas Valley, Lakeview, Ontario, Prairie City, Echo, Hermiston R&E and Hermiston (Boardman). Your OSU Extension agent or local experiment station can be of assistance in supplying further information or contact the U.S. Bureau of Reclamation Conservation Program Manager in Boise, Idaho.
In general, the application efficiency of an irrigation system depends on the particular type of system. Application efficiency results from the amount of control the irrigator has over the ultimate distribution of water. It follows that surface irrigation systems are generally less efficient than sprinkle and drip irrigation systems. Several publications are available which give the irrigator an estimate of application efficiencies for different system types (PNW 288, SCS National Engineering Handbook: Section 15, Chapter 2). Equipment design and maintenance and water management also play an important part in application efficiency and cannot be neglected. See Appendix B for definitions of application efficiency and distribution uniformity.
There are various means of numerically describing irrigation performance. Two of these are application efficiency (Ea) and distribution uniformity (DU). Application efficiency is defined as the ratio of the volume of irrigation water beneficially used to the volume of irrigation water applied (ASCE, 1978). Beneficial uses include cooling, frost protection and leaching to control salinity in the root zone. Distribution uniformity is a measure of how evenly water infiltrates the ground across a field during irrigation and is expressed as a percentage between 0 and 100. It is defined as the ratio of the average low-quarter depth of infiltration to the average depth of infiltration. Good distribution uniformity is essential for reducing deep percolation if the entire field is to be watered sufficiently.
Aquifer A geological formation capable of yield usable quantities of water to wells or springs
Application A measure of how much of the water applied to a field during an efficiency (Ea) irrigation is beneficially used. Beneficial uses include crop evapotranspiration (ET), frost control, leaching for salt control and cooling. See Appendix A.
Best management A generic term referring to schedules of activities, prohibitions of practices (BMP) practices, maintenance procedures and other management practices to prevent or reduce the pollution of ground or surface water.
Calibration To check and adjust application equipment so that the desired application rate is achieved.
Cascading Flows Movement of water from a high aquifer to a lower aquifer through well boreholes.
Chemigation The application of formulated liquids or solutions of pesticides, herbicides, fungicides, fertilizers or other agents through the irrigation system.
Clean Water Act A Federal enactment (1972) seeking to maintain the chemical, (CWA) physical and biological integrity of the nation's waters. Administrative authority is given to the U.S. Environmental Protection Agency (EPA) and requirements are carried out by the Oregon Department of Environmental Quality. Section 319 covers non-point source pollution.
Cutback irrigation Reducing the inflow rate of irrigated furrows after the completion of advance.
Deep percolation The movement of soil-water past the crop root zone.
Distribution A measure of how evenly water is applied/infiltrated in a field uniformity (DU) during an irrigation.
Evapotranspiration The sum total of plant transpiration and soil surface evaporation in (ET) a cropped field.
Fertigation The application of fertilizers through the irrigation system.
Flume A flow measurement structure for use with open channels.
Integrated pest A combination of pesticide and non-pesticide methods to control management (IPM) pests. Methods include cultural practices, use of biological, physical, and genetic control agents, and the selective use of pesticides.
Irrigation scheduling A generic term used to describe a family of methods/techniques that aid a farmer in deciding when to irrigate and how much water to apply.
Leaching The movement of chemicals through soil with water.
Nonpoint source Pollution caused by diffuse sources that are not regulated as a point pollution (NPS) source.
OACFA Oregon Agricultural Chemical and Fertilizer Association.
Polyacrylamide A synthetic long-chain polymer used to reduce erosion by (PAM) increasing soil cohesion and flocculating sediments when applied with irrigation water.
Root zone The effective depth of crop roots in the soil from which water is extracted.
Soil Stabilizing
Crops Crops planted specifically to reduce movement of surface soils due to wind or water erosion.
Surge-flow A technique employed with furrow irrigation to increase uniformity and to reduce runoff by intermittently introducing pulses of irrigation water into a furrow
SWCD Soil Water Conservation District
Tailwater Irrigation runoff from surface irrigated fields.
Wellhead The surface and subsurface area surrounding a water well or wellfield supplying a public water system through which contaminants are likely to move toward and reach such water well or wellfield.
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