Furrow erosion was recognized as a serious problem damaging cropland 40
years ago (Israelson et al., 1946), and attempts to quantify soil loss in
relation to furrow stream size and slope were made then and in the following
few years (Gardner and Lauritzen, 1946; Mech, 1959). However, little attention
was given to these studies, and the furrow erosion problem continued without
much effort to correct it for another 25 years. In the early 1970's water
quality legislation was directed towards reducing sediment, nutrients and
biocides in irrigation return flows. As scientists began to develop methods
to improve the quality of irrigation return flows in response to this legislation,
some questions were raised about the sources of these pollutants. Brown et el.,
(1974), and Carter at al., (1974) reported sediment and phosphorus inflows,
outflows, and balances for two large irrigation tracts in south central Idaho.
They found large quantities of sediment and associated phosphorus were being
lost from many irrigated fields. Research has progressed during the life of
the STEEP project, and much new information about erosion and sediment loss
has been reported both at Kimberly, Idaho, and Prosser, Washington. This paper
is a summary of the progress made towards understanding and controlling irrigation
erosion and sediment loss

Carter, D.L.

Miller, D.E.

Furrow erosion was recognized as a serious problem damaging cropland 40
years ago (Israelson et al., 1946), and attempts to quantify soil loss in
relation to furrow stream size and slope were made then and in the following
few years (Gardner and Lauritzen, 1946; Mach, 1959). However, little attention
was given to these studies, and the furrow erosion problem continued without
much effort to correct it for another 25 years. In the early 1970's water
quality legislation was directed towards reducing sediment, nutrients and
biocides in irrigation return flows. As scientists began to develop methods
to improve the quality of irrigation return flows in response to this legislation,
some questions were raised about the sources of these pollutants. Brown et al.,
(1974), and Carter et al., (1974) reported sediment and phosphorus inflows,
outflows, and balances for two large irrigation tracts in south central Idaho.
They found large quantities of sediment and associated phosphorus were being
lost from many irrigated fields. Research has progressed during the life of
the STEEP project, and much new information about erosion and sediment loss
has been reported both at Kimberly, Idaho, and Prosser, Washington. This paper
is a summary of the progress made towards understanding and controlling irrigation
erosion and sediment loss

USDA - ARS - NWISRL

MfiSTth Lury,STEEP Symposium. May 20-21, 1986. Spokane, Washington. pp. 585-591	 #4041. -FURROW IRRIGATION EROSION AND ITS CONTROLD. L. Carter and D. E. MillerSupervisory Soil Scientist and Research Soil Scientist,USDA, Agricultural Research Service, Kimberly, Idaho, andProsser, Washington, respectively.Sediment yield, residue management, sedimentation, furrow erosion rates,conservation tillage.INTRODUCTIONFurrow erosion was recognized as a serious problem damaging cropland 40years ago (Israelson et al., 1946), and attempts to quantify soil loss inrelation to furrow stream size and slope were made then and in the followingfew years (Gardner and Lauritzen, 1946; Mach, 1959). However, little attentionwas given to these studies, and the furrow erosion problem continued withoutmuch effort to correct it for another 25 years. In the early 1970's waterquality legislation was directed towards reducing sediment, nutrients andbiocides in irrigation return flows. As scientists began to develop methodsto improve the quality of irrigation return flows in response to this legislation,some questions were raised about the sources of these pollutants. Brown et al.,(1974), and Carter et al., (1974) reported sediment and phosphorus inflows,outflows, and balances for two large irrigation tracts in south central Idaho.They found large quantities of sediment and associated phosphorus were beinglost from many irrigated fields. Research has progressed during the life ofthe STEEP project, and much new information about erosion and sediment losshas been reported both at Kimberly, Idaho, and Prosser, Washington. This paperis a summary of the progress made towards understanding and controlling irrigationerosion and sediment loss.FURROW EROSION AND SEDIMENT LOSSThe irrigation furrow serves two purposes. One is to convey water fromthe top of the field 'to the bottom to supply water for infiltrating into thesoil. The other is to function as the infiltrating surface for water to enterthe soil. The stream size needed depends upon the soil infiltration rate, therun length, the furrow slope and factors such as roughness and residue thatdissipate energy of flowing water and slow the flow velocity. Some of thesefactors depend upon others. For example, residue usually increases infiltrationwhich decreases stream size, thereby requiring a larger stream to reach thedownslope field end. The stream required for infiltration is small, but thatrequired for transporting water to meet that infiltration need over the entirefurrow length is much larger and usually exceeds the erosive stream size onthe upslope one-third of the field. Irrigation management, which reflects theirrigator's judgment, is also an important factor. Often stream sizes are toolarge on steep slopes, and severe erosion occurs.Berg and Carter (1980) made detailed measurements of sediment losses fromfurrow erosion with different crops over a slope range of 1.0 to 4.0 percent.From these and other data collected later by these and other researchers, atable of sediment losses has been developed (Table 1). These data illustrate585the importance of land slope and crop on sediment losses. The presence andseverity of the convex end also has a significant impact on sediment loss. Aconvex and is an increasing slope into the tailwater ditch over the lower 20to 60 ft of furrow (Carter and Berg, 1983). The data reported in Table 1represent average sediment losses under irrigator's management. The actualfield observations show wide variation. Much of this variation is associatedwith wide variation in the furrow stream size applied. The average runoff fromall fields was 50 percent of the water applied, indicating that larger streamsthan needed were uplied (Berg and Carter, 1980). Sediment losses are higherwhere unlined ditches with cut-outs or gated pipe are used because variationin stream is greater.Table 1.--Estimated seasonal sediment losses in tons/a for different crops irrigatedfrom cement lined ditches with siphon tubes. Run length was 660 ft. 	 'Average Field Slope, %----0.5-1-- 	 	 1-2 	 	 2-3 	 	 >3Convex end N N S N M S N M S N M SCrapAlfalfa 0.0 0.0 0.0 0.7 0.9 1.2 2.3 2.9 4.1 5.6 7.0 9.8Cereal grainor peas 1.1 1.3 1.8 3.2 4.0 5.6 6.4 8.0 11.2 10.4 13.0 18.2Dry beansor corn 2.5 3.1 4.4 8.7 10.9 15.3 18.4 23.0 32.2 28.0 35.0 49.0Sugarbeets 3.2 4.0 5.6 12.1 15.2 21.2 26.4 33.0 46.2 44.0 55.0 77.0N no convex end; 24 moderate convex end; S severe convex endCONTROLLING FURROW EROSIONAND SEDIMENT LOSSIn response to legislation, the first efforts to improve the quality of irrigationreturn flows were directed towards removing sediment from drainage waters justbefore these waters entered streams or rivers. Subsequent research has beendirected toward reducing sediment losses from individual farms and fields, andfinally to reducing the source of sediment by controlling erosion. Followingare brief discussions of control practices developed and evaluated during thelife of the STEEP program.Sediment Retention BasinsSeveral types of sediment retention basins ranging from 1.0 acre or more locatedon a main drain to mini-basins receiving runoff from only four or five furrowshave been evaluated. All are effective and each has an effective application.Large sediment basins are often created by constructing an earthen dam acrossa natural drainage at a suitable site and installing a proper outlet. Theselarge basins have sediment removal efficiencies of 65 to 95 percent, dependingupon the sediment concentration in the inflow and the time required for water586to pass through the basin (Brown at al., 1981). Medium sized basins are oftenexcavations receiving runoff water from one or more fields. Their sedimentremoval efficiencies range from 75 to 95 percent. Mini-basins are formed byexcavating a sequence of small basins along the lower end of a field or byplacing earthen checks across the tailwater drainage ditch and extending themacross the convex end where present. If controlled outlets into a separatedrainage ditch are placed in each mini-basin, the sediment removed efficienciesrange from 85 to 95 percent. If water is allowed to pass from one basin tothe net, efficiencies are only 40 to 70 percent, and often flow volumes destroythe basins by washing out the earthen checks (Brown at al., 1981; Carter andBerg, 1983).Another type of mini-basin is the "I-slot" or "T-slot", constructed by excavatinga 6 to 10 ft section in the shape of an "I" or "T". A series of these slotsare constructed along the tailwater ditch. Efficiencies of these basins areabout the same as for other mini-basins where the water flows from one to theother, or about 40 to 70 percent. These slots, however, because they are belowthe level of the ditch bottom, are not susceptible to being destroyed by thedrainage stream.Sediment basins are costly to maintain because they need cleaning and theremoved sediment must be transported. We recommend that where possible, basinsbe located in naturally low areas that can be farmed as part of an adjacentfield once they are filled with sediment.The Soil Conservation Service and the Extension Service in Idaho, Oregon, andWashington can provide information on the design and appropriate type of sedimentbasins to use for various field and farm situations. Cost share funds may beavailable under several programs in many irrigated areas within these states.Buried Pipe Runoff and Sediment Control SystemIn an attempt to correct convex end problems on many fields, Carter and Berg(1983) developed a system comprised of a buried drain pipe along the lower endof a field in place of the drainage ditch. Vertical inlets at intervals alongthe pipe allow drainage water to enter. An earthen dam is constructed immediatelydownslope from each inlet, and the top of the inlet is placed at the elevationto eliminate the convex end once the area between the dam fills to the top ofthe inlet pipe with sediment. The first season this system functions much thesame as mini-basins with separate outlets and is 85 to 95 percent efficientfor removing sediment. After the convex end is corrected, the efficiencydecreases to 75 to 90 percent, but the incoming sediment load is much smallerbecause the convex end no longer exists and the high erosion rate along theconvex end has been eliminated. The area once barren as a convex end can befarmed adding to crop production, and tailwater ditches that could not becrossed with equipment are eliminated. Weed control problems along the lowerfield end are also reduced.The initial cost of the buried pipe runoff and sediment control system is higherthan that of some other practices, but it has the potential of paying for itselfin 4 to 8 years by correcting convex end and tailwater control problems andadding productive area to fields. This increased production increases the netincome from the field. This system requires little or no maintenance afterthe convex end is corrected.587Vegetative Filter Strips Strips of cereal grain, grass or alfalfa seeded along the lower ends offields can reduce sediment .losses by 40 to 60 percent, depending upon thesediment load in the runoff water, placement of the vegetation filter stripand how far furrows are made into the strip. Thesepegetative filter stripscan be harvested for some return from the land, but yields per unit area Oreusually 50 to 70 percent of field yields. Such filter strips can also be placedalong upper ends of fields or on particularly steep segments where the furrowstreams exceed erosive size. Vegetative filter strips must be properly installedand managed if they are to be effective. They are a relatively low costalternative, but their effectiveness is less than that of some other erosionand sediment loss control alternatives.Use og Crop Residues to Contrql Furysw ErosionThe proper use of crop residues is a valuable tool to control soil erosionunder natural precipitation (Larson et al., 1978). Similar benefits shouldoccur with sprinkler irrigation. Crop residues also effectively reduce erosionduring furrow irrigation. At Prosser, Washington, Aarstad and Miller (1981)found that relatively small amounts of straw (500 to 1000 lbs/a of furrow area)almost eliminated furrow erosion and the sediment load in the outflow water.Brown (1985) obtained similar results at Kimberly, Idaho. Miller and Aarstad(1983) observed that with corn or wheat residue from the previous year's crop,limited tillage could be performed for seed bed preparation and herbicideincorporation with enough residue remaining in the furrows to effectively reduceerosion.An important-problem with furrow irrigation is the non-uniformity ofwetting along the furrows, especially when the soil is loose and the infiltrationrate is high, such as during the first irrigation of the season or aftercultivation. By the time the furrow stream advances to the bottom end of afield, the upper end may be overirrigated. All of the above studies have shownthat residues in the furrows increase infiltration rates by 50% or more, furtheraggravating the non-uniformity of wetting.Surge flow refers to an irrigation system in which the furrow stream isalternately ON and OFF for the desired period of time - 0.5 hr ON and 0.5 hrOFF, for example (Stringham and Keller, 1979; Bishop et al., 1981). It hasbeen found that furrow streams advance as fast or faster with surging than withcontinuous flow. Inasmuch as the total amount of water applied by surge flowis only one-half that used in continuous flow (water is applied to the furrowonly one-half of the time in surge flow) the uniformity of wetting along thefurrow when outflow begins is much better with surge than with continuous flow(Evans at al., 1985).In recent years Evans at al. (1985) at Prosser have been evaluating thecombination of residues in furrows and surge flow irrigation to control erosionand increase wetting uniformity. The residues allow large furrow streams andrapid advance without excessive erosion, and surge flow increases uniformityof wetting. This work has shown that large furrow streams can be used withoutexcessive erosion, if the furrows contain residues, whether the residues arehand-placed or grown on site (Table 2). The furrow stream of 8.0 gal/min isvery high for this soil and slope, 3.0 gal/min would be more usual. Even with588fable 2.--Instantaneous rate of sediment discharge from furrows as affectedby straw placed in the furrows (1983) or wheat and corn residuesgrown /n situ (1985). Measurements were made soon after outflowbegan with a furrow inflow of 8.0 gal/min. After the measurements,the furrow stream was reduced to just maintain outflow. In 1985,on* surge flow was used during the advance phase.Straw '	1983	1985rates	 Surge Continuous	 Residue+	SurgeTon/a	 Ton a- l/day' l	Ton a-1/day- 10 78.8 63.3 0 53.71 0.8 0.2 wheat 0.62 0.2 0.1 corn 0.41Hand-placed in furrowsTGrown inxiIm50450(r) 40VI 35'421 30to25vi 20U)0 sa 1 0cn54	 1983---014--1984	 1985 -0-1983-84 STRAW 1	 a	 1 1985 RESIDUE15 30115	 15 30 115	 1984	 1985-01015 ft.3014-19830.5 1 STRAW11.0a El CORNi a	 i 0 NONE0 Tons/a1ab1111111111	bbb 	 lagiab b7:1:3aFig. 1.--Seasonal furrow erosion at three distances from theupper end of the furrows as affected by residues in the furrows.Bars within each group of three with different letters representsignificantly different values of F.m0.05 or less.589^^53. Berg, R. D. and D. L. Carter. 1980. Furrow erosion and sediment losseson irrigated cropland. J. Soil Water Conserv. 35:267-270.4. Bishop, A. A., S. R. Walker, N. L. Allen, and G. J. Poole. 1981. Furrowadvance rates under surge flow systems. 3. Irrig. and Drainage Div., Am.Soc. Civ. Eng., 107: (No. IR3) 257-264.5. Brown, M. 3. 1985. Effect of grain straw and furrow irrigation streamsize on soil erosion and infiltration. J. Soil Water Conserv. 43:389-391.6. Brown, M. J., J. A. Bondurant and C. E. Brockway. 1981. Ponding surfacedrainage water for sediment and phosphorus removal. Trans. Am. Soc. Agr.Eng. 24:1478-1481.7. Brown, M. J., D. L. Carter, and J. A. Bondurant. 1974. Sediment inirrigation and drainage waters and sediment inputs and outputs for twolarge irrigation tracts in southern Idaho. J. Environ. Qual. 3:347-351.8. Carter, D. L. and R. D. Berg. 1983. A buried pipe system for controllingerosion and sediment loss on irrigated land. Soil Sci. Soc. Am. J.47:749-752.9. Carter, D. L., M. J. Brown, C. W. Robbins, and J. A. Bondurant. 1974.Phosphorus associated with sediments in irrigation and drainage watersfor two large tracts in southern Idaho. J. Environ. (Nal. 3:287-291.10. Evans, R. C., J. S. Aarstad, D. E. Miller, and M. Kroeger. 1985. cropresidue effects on furrow advance and infiltration. Paper No. 85-2586,Am. Soc. Agr. Eng. Annual Meeting, Chicago, IL./1. Gardner, W. and C. W. Lauritzen. 1946. Erosion as a function of the sizeof the irrigating stream and the slope of the eroding surface. Soil Sci.62:233-242.12. Israelson, 0. W., G. D. Clyde, and C. W. Lauritzen. 1946. Soil erosionin small irrigation furrows. Utah Agr. Exp. Sta. Bul. 320.13. Larson, W. E., R. F. Holt, and C. W. Carlson. 1978. Residues for soil• conservation. In W. R. Oschwald (ed.) Crop Residue Management Systems,Am. Soc. Agron., Madison, WI. pp. 1-18.14. Mech, S. J. 1959. Soil erosion and its control under furrow irrigationin the arid vest. Info. Bul. 184, Agr. Res. Serv., U. S. Dept. Agr.,Washington, D. C.15. Miller, D. E. and J. S. Aarstad. 1983. Residue management to reducefurrow erosion. J. Soil Water Conserv. 38:366-370.16. Stringham, G. E., and J. Keller. 1979. Surge flow for automatic irrigation.Proc. Irrig. and Drainage Div. Specialty Conf., Am. Soc. Civ. Eng.,Albuquerque, NM, pp. 132-142.591

Furrow Irrigation Erosion and Its Control

Northwest Irrigation & Soils Research Laboratory Publications

Furrow irrigation erosion and its control

n STEEP - Conservation Concepts and Accomplishments. Washington State UniversityPublication, Pullman, Washington. May, 1987. pages 585-591FURROW IRRIGATION EROSION AND ITS CONTROLD. L. Carter and D. E. MillerSupervisory Soil Scientist and Research Soil Scientist,USDA, Agricultural Research Service, Kimberly, Idaho, andProsser, Washington, respectively.Sediment yield, residue management, sedimentation, furrow erosion rates,conservation tillage.INTRODUCTIONFurrow erosion was recognized as a serious problem damaging cropland 40years ago (Israelson et al., 1946), and attempts to quantify , soil loss inrelation to furrow stream size and slope were made then and in the followingfew years (Gardner and Lauritzen, 1946; Mech, 1959). However, little attentionwas given to these studies, and the furrow erosion problem continued withoutmuch effort to correct it for another 25 years. In the early 1970's waterquality legislation was directed towards reducing sediment, nutrients andbiocides in irrigation return flows. As scientists began to develop methodsto improve the quality of irrigation return flaws in response to this legislation,some questions were raised about the sources of these pollutants. Brown et el.,(1974), and Carter at al., (1974) reported sediment and phosphorus inflows,outflows, and balances for two large irrigation tracts in south central Idaho:They found large quantities of sediment and associated phosphorus were beinglost from many irrigated fields. Research has progressed during the life ofthe STEEP project, and much new information about erosion and sediment losshas been reported both at Kimberly, Idaho, and Prosser, Washington. This paperis a summary of the progress made towards understanding and controlling irrigationerosion and sediment loss.FURROW EROSION AND SEDIMENT LOSSThe irrigation furrow serves two purposes. One is to convey water fromthe top of the field to the bottom to supply water for infiltrating into thesoil. The other is to function as the infiltrating surface for water to enterthe soil. The stream size needed depends upon the soil infiltration rate, therun length, the furrow slope and factors such as roughness and residue thatdissipate energy of flowing water and slow the flow velocity. Some of thesefactors depend upon others. For example, residue usually increases infiltrationwhich decreases stream size, thereby requiring a larger stream to reach thedownsIope field end. The stream required for infiltration is small, but thatrequired for transporting water to meet that infiltration need over the entirefurrow length is much larger and usually exceeds the erosive stream size onthe upslope one-third of the field. Irrigation management, which reflects theirrigator's judgment, is also an important factor. Often stream sizes are toolarge on steep slopes, and severe erosion occurs.Berg and Carter (1980) made detailed measurements of sediment losses fromfurrow erosion with different crops over a slope range of 1.0 to 4.0 percent.From these and other data collected later by these and other researchers, atable of sediment losses has been developed (Table 1). These data illustrate585the importance of land slope and crop on sediment losses. The presence andseverity of the convex end also has a significant impact on sediment loss. Aconvex end is an increasing slope into the tailwater ditch over the lower 20to 60 ft of furrow (Carter and Berg, 1983). The data reported in Table 1represent average sediment losses under irrigator's management. The actualfield observations show wide variation. Much of this variation is associatedwith wide variation in the furrow stream size applied. The average runoff fromall fields was 50 percent of the water applied, indicating that larger streamsthan needed were applied (Berg and Carter, 1980). Sediment losses are higherwhere unlined ditches with cut-outs or gated pipe are used because variationin stream is greater.Table ' 1.--Estimated seasonal sediment losses in tons/a for different crops irrigatedfrom cement lined ditches with siphon tubes.Average Field Slope, %----0.5-1-- 1-2 	Convex end	 N	 M	 S	 NgkmRun length was 660 ft.	 	 2-3 	 	 	 >3M	 S	 N	 XAlfalfa 0.0 0.0 0.0 0.7 0.9 1.2 2.3 2.9 4.1 5.6 7.0 9.8Cereal grainor peas 1.1 1.3 1.8 3.2 4.0 5.6 6.4 8.0 11.2 10.4 13.0 18.2Dry beansor corn 2.5 3.1 4.4. 8.7 10.9 15.3 18.4 23.0 32.2 28.0 35.0 49.0Sugarbeets 3.2 4.0 5.6 12.1 15.2 21.2 26.4 33.0 46.2 44.0 35.0 77.0N no convex end; M - moderate convex end; S severe convex endCONTROLLING FURROW EROSIONAND SEMMENT LOSSIn response to legislation, the first efforts to improve the quality of irrigationreturn flows were directed towards removing sediment from drainage waters justbefore these waters entered streams or rivers. Subsequent research has beendirected toward reducing sediment losses from individual farms and fields, andfinally to reducing the source of sediment by controlling erosion. Followingare brief discussions of control practices developed and evaluated during thelife of the STEEP program.Sediment Retention Basins Several types of sediment retention basins ranging .1.t..4a 1.0 acre or more locatedon a main drain.to mini-basins receiving runoff from only four or five furrowshave been evaluated. All are effective and each has an effective application.Large sediment basins are often created by constructing an earthen dam acrossa natural drainage at a suitable site and installing a proper outlet. Theselarge basins have sediment removal efficiencies of 65 to 95 percent, dependingupon the sediment concentration in the inflow and the time required for water586to pass through the basin (Brown et al., 1981). Medium sized basins are oftenexcavations receiving runoff water from one or more fields. Their sedimentremoval efficiencies range from 75 to 95 percent. Mini-basins are formed byexcavating a sequence of small basins along the lower end of a field or byplacing earthen checks across the tailwater drainage ditch and extending themacross the convex end where present. If controlled outlets into a separatedrainage ditch are placed in each mini-basin, the sediment removed efficienciesrange from 85 to 95 percent. If water is allowed to pass from one basin tothe next, efficiencies are only 40 to 70 percent, and often flow volumes destroythe basins by washing out the earthen checks (Brown et *1., 1981; Carter andBerg, 1983).Another type of mini-basin is the "I-slot" or "T-slot", constructed by excavatinga 6 to 10 ft section in the shape of an "I" or "T". A series of these slotsare constructed along the tailwater ditch. Efficiencies of these basins areabout the same as for other mini-basins where the water flows from one to theother, or about 40 to 70 percent. These slots, however, because they are belowthe level of the ditch bottom, are not susceptible to being destroyed by thedrainage stream.Sediment basins are costly to maintain because they need cleaning and theremoved sediment must be transported. We recommend that where possible, basinsbe located in naturally low areas that can be farmed as part of an adjacentfield once they are filled with sediment.The Soil Conservation Service and the Extension Service in Idaho, Oregon, andWashington can provide information on the design and appropriate type of sedimentbasins to use for various field and farm situations. Cost share funds may beavailable under several programs in many irrigated areas within these states.Buried Pine Runoff and Sediment Control SystemIn an attempt to correct convex end problems on many fields, Carter and Berg(1983) developed a system comprised of a buried drain pipe along the lower endof a field in place of the drainage ditch. Vertical inlets at intervals alongthe pipe allow drainage water to enter. An earthen dam is constructed immediatelydovnslope from each inlet, and the top of the inlet is placed at the elevationto eliminate the convex end once the area between the dam fills to the top ofthe inlet pipe with sediment. The first season this system functions much thesame as mini-basins with separate outlets and is 85 to 95 percent efficientfor removing sediment. After the convex end is corrected, the efficiencydecreases to 75 to 90 percent, but the incoming sediment load is much smallerbecause the convex end no longer exists and the high erosion rate along theconvex end has been eliminated. The area once barren as a convex end can befarmed adding to crop production, and tailwater ditches that could not becrossed with equipment are eliminated. Weed control problems along the lowerfield end are also reduced.The initial cost of the buried pipe runoff and sediment control system is higherthan that of some other practices, but it has the potential of paying for itselfin 4 to 8 years by correcting convex end and tailwater control problems andadding productive area to fields. This increased production increases the netincome from the field. This system requires little or no maintenance afterthe convex end is corrected.587Vegetative Filter Strins Strips of cereal grain, grass or alfalfa seeded along the lower ends offields can reduce sediment losses by 40 to 60 percent, depending upon thesediment load in the runoff water, placement of the vegetation filter stripand how far furrows are made into the strip. These vegetative filter stripscan be harvested for some return from the land, but yields per unit area areusually 50 to 70 percent of field yields. Such filter strips can also be placedalong upper ends of fields or on particularly steep segments where the furrowstreams exceed erosive size. Vegetative filter strips must be properly installedand managed if they are to be effective. They are a relatively low costalternative, but their effectiveness is less than that of some other erosionand sediment loss control alternatives.Use of Cron Residues to Control Furrow ErosionThe proper use of crop residues is a valuable tool to control soil erosionunder natural precipitation (Larson et al., 1978). Similar benefits shouldoccur with sprinkler irrigation. Crop residues also effectively reduce erosionduring furrow irrigation. At Prosser, Washington, Aarstad and Miller (1981)found that relatively small amounts of straw (500 to 1000 lbs/a of furrow area)almost eliminated furrow erosion and the sediment load in the outflow water.Brown (1985) obtained similar results at Kimberly, Idaho. Miller and Aarstad(1983) observed that with corn or wheat residue from the previous year's crop,limited tillage could be performed for seed bed preparation and herbicideincorporation with enough residue remaining in the furrows to effectively reduceerosion.An important problem with furrow irrigation is the non-uniformity ofwetting along the furrows, especially when the soil is loose and the infiltrationrate is high, such as during the first irrigation of the season or aftercultivation. By the time the furrow stream advances to the bottom end of afield, the upper end may be overirrigated. All of the above studies have shownthat residues in the furrows increase infiltration rates by 50% or more, furtheraggravating the non-uniformity of wetting.Surge flow refers to an irrigation system in which the furrow stream isalternately ON and OFF for the desired period of time - 0.5 hr ON and 0.5 hrOFF, for example (Stringham and Keller, 1979; Bishop et al., 1981). It hasbeen found that furrow streams advance as fast or faster with surging than withcontinuous flow. Inasmuch as the total amount of water applied by surge flowis only one-half that used in continuous flow (water is applied to the furrowonly one-half of the time in surge flow) the uniformity of wetting along thefurrow when outflow begins is much better with surge than with continuous flow(Evans et al., 1985).In recent years Evans et al. (1985) at Prosser have been evaluating thecombination of residues in furrows and surge flow irrigation to control erosionand increase wetting uniformity. The residues allow large furrow streams andrapid advance without excessive erosion, and surge flow increases uniformityof wetting. This work has shown that large furrow streams can be used withoutexcessive erosion, if the furrows contain residues, whether the residues arehand-placed or grown on site (Table 2). The furrow stream of 8.0 gal/min isvery high for this soil and slope, 3.0 gal/min would be more usual. Even with5881a aaTable 2.--Instantaneous rate of sediment discharge from furrows as affectedby straw placed in the furrows (1983) or wheat and corn residuesgrown in situ (1985). Measurements were made soon after outflowbegan with a furrow inflow of 8.0 gal/min. After the measurements,the furrow stream was reduced to just maintain outflow. In 1985,only surge flow was used during the advance phase.Straw '	1983	1985rates	Surge Continuous	 Residuet	SurgeTon a-1/day-1	 Ton a- 1/day- 1Ton/a0 78.8 53.31 0.8 0.22 0.2 0.10	 53.7wheat	0.6corn	0.4'Hand-placed in furrowsTGrown in situ1 984-•14--19851985 RESIDUE0 NONESTRAWCORN	 983 	 bi450 1983-84 STRAW0 Tons/a	 1 aa7 450 0.5Icr) 40 1.0	 135CaI% 30tn0 25 btr; 200 150 10U)5•1b1bIb bb5 ft 30 115 I 15	 30 115	 15	 30 115I4----1983 1 1 4'	 1984 ' 1.4	 1985---1Fig. 1.--Seasonal furrow erosion at three distances from theupper end of the furrows as affected by residues in the furrows.Bars within each group of three with different letters representsignificantly different values of P ...0.05 or less.589such a large furrow stream, sediment loss was negligible from the furrowscontaining crop residues.Sediment concentration in the runoff from surged flow was usually greaterthan with continuous flow (Table 2). However, because of the lower totaloutflow from surging, total sediment loss was less with surge than with continuousflow. The difference between surge and continuous flow was small compared tothat between the presence or absence of residues.Seasonal soil losses along the furrows are summarized in Figure 1. In1983 and 1985 furrow inflow was 8.0 gal/min until outflow started, when it wasreduced to just maintain outflow. In 1984 furrow inflow was 6.0 gal/min withno reduction. Sail was lost from all furrows near the top of the field wherethe furrow stream was the largest. At any location, the soil lost was muchless with than without residues in the furrows, especially where the residueswere grown in situ.Conservation ' Tillaze on Furrow Irrigated LandNo-till and minimum-till practices have been studied on furrow irrigatedland for one season. Results are promising, but more research and evaluationare needed to develop the best systems. Early results indicate that winterand spring wheat and corn can be successfully grown following alfalfa withouttillage. Erosion and sediment losses were essentially eliminated by applyingno till management. Additional research is underway on this subject.SIMMARYFurrow erosion was recognized as a serious problem in the 1940's and somesattempts to quantify relationships among slope, furrow stream size and erosionwere made. Water quality legislation in the early 1970's mandated attentiontowards irrigation return flow quality problems. Research for the past 15years has developed and evaluated alternative management practices to reducesediment loss and decrease erosion. The first efforts were to remove sedimentfrom runoff water before it entered rivers or streams. Sediment basins,mini-basins, buried pipe runoff and sediment control systems and vegetativefilter strips, were all effective alternatives for removing sediment from runoffwater. Small amounts of crop residues effectively reduce erosion during furrowirrigation. Surge flow and residues can be combined to improve wettinguniformity. The residues allow large furrow streams and rapid advance withoutexcessive erosion while surge flow allows more nearly uniform wetting duringfurrow stream advance. Differences in erosion between surge and continuousflow are small compared to those between the presence and absence of residues.Conservation tillage is a promising practice to control both erosion and sedimentloss from furrow irrigated land.REFERENCES1. Aarstad, J. S. and D. E. Miller. 1981.. Effects of small amounts ofresidue on furrow erosion. Soil Sci. Soc. Am. J. 45:116-118.2. Berg. R. D. 1984. Straw residue to control furrow erosion on sloping,irrigated land. J. Soil Water Conserv. 39:58-60.5903. Berg, R. D. and D. L. Carter. 1980. Furrow erosion and sediment losseson irrigated cropland. J. Soil Water Conserv. 35:267-270.4. Bishop, A. A., S. R. Walker, N. L. Allen, and G. J. Poole. 1981. Furrowadvance rates under surge flow systems. J. Irrig. and Drainage Div., Am.Soc. Civ. Eng., 107: (No. 113) 257-264.5. Brown, M. J. 1985. Effect of grain straw and furrow irrigation streamsize on soil erosion and infiltration. J. Soil Water Conserv. 40:389-391.6. Brown, M. J., J. A. Bondurant and C. E. Brockway. 1981. Ponding surfacedrainage water for sediment and phosphorus removal. Trans. Am. Soc. Agr.Eng. 24:1478-1481.7. Brown, M. J., D. L. Carter, and J. A. Bondurant. 1974. Sediment inirrigation and drainage waters and sediment inputs and outputs for twolarge irrigation tracts in southern Idaho. J. Environ. (Mal. 3:347-351.8. Carter, D. L. and R. D. Berg. 1983. A buried pipe system for controllingerosion and sediment loss on irrigated land. Soil Sci. Soc. Am. J.47:749-752.9. Carter, D. L., M. J. Brown, C. W. Robbins, and J. A. Bondurant. 1974.Phosphorus associated with sediments in irrigation and drainage watersfor two large tracts in southern Idaho. J. Environ. Qual. 3:287-291.10. Evans, R. G., J. S. Aarstad, D. E. Miller, and M. Kroeger. 1.985. cropresidue effects on furrow advance and infiltration. Paper No. 85-2586,Am. Soc. Agr. Eng. Annual Meeting, Chicago, IL.11. Gardner, W. and C. W. Lauritzen. 1946. Erosion as a frxiction of the sizeof the irrigating stream and the slope of the eroding surface. Soil Sci.62:233-242.12. Israelson, 0. W., G. D. Clyde, and C. W. Lauritzen. 1946. Soil erosionin small irrigation furrows. Utah Agr. Exp. Sta. Bul. 320.13. Larson, W. E., R. F. Holt, and G. W. Carlson. 1978. Residues for soil• conservation. /n W. R. Oschwald (ed.) Crop Residue Management Systems,Am. Soc. Agron., Madison, WI. pp. 1-18.14. Mech, S. J. 1959. Soil erosion and its control under furrow irrigationin the arid west. Info. Bul. 184, Agr. Res. Serv., U. S. Dept. Agr.,Washington, D. C.15. Miller; D. E. and J. S. Aarstad. 1983. Residue management to reducefurrow erosion. J. Soil Water Conserv. 38:366-370.16. Stringham, G. E., and J. Keller. 1979. Surge flow for automatic irrigation.Proc. Irrig. and Drainage Div. Specialty Conf., Am. Soc. Civ. Eng.,Albuquerque, NM, pp. 132-142.591

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Furrow irrigation erosion and its control

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