Shrub Species for Single-Row Field Windbreaks Under Center-Pivot Irrigation Systems

Copyright ©  2008  Regents of the University of Minnesota. All rights reserved.

Table of Contents

Introduction

Single-row tree windbreaks have been protecting Minnesota fields from wind erosion for many years. In recent years, however, tree windbreaks have often been topped or removed to accommodate the traveling booms of center-pivot irrigation systems. These systems are normally installed on sandy, droughty soils that are highly susceptible to wind erosion. Without a substitute for the windbreaks, there could be a return to the "sand-blasting" damage to young crops caused by dust storms, damage which can require the replanting of crops a second or even a third time.

New installations of center-pivot irrigation systems have increased sharply in the last 20 years. The number of acres under center-pivot systems in the Bonanza Valley of west central Minnesota increased from an estimated 1,000 acres in 1966 to 23,000 acres in 1976 (Sperbeck and D'Silva, 1978) and from approximately 45,000 to 50,000 acres in 1990.¹ The entire state of Minnesota had an estimated 100,000 acres under center-pivot irrigation systems in 1975 and that number had risen to 500,000 acres in 1990.² This is an average annual increase of over 26,000 acres during the last 15 years.

As the number of acres under center-pivot irrigation increased, more windbreaks were removed and farmers had to seek alternative barriers. Frequently they looked to shrubs or grass strips as a solution. They began asking windbreak specialists for recommendations on shrub species that could perform the windbreak functions. Since shrub species have only rarely been used in field windbreaks, windbreak specialists had to base their recommendations on past performance of shrub species in farmstead shelterbelts and ornamental plantings.

To make valid recommendations, it was necessary for specialists to test various shrub species under center-pivot irrigation systems. During 1978, the following cooperating agencies made plans for a 10-year shrub testing project at the Herman Rosholt Research Farm, Westport, Minnesota:

Pope County Soil and Water Conservation District (SWCD), Glenwood, Minnesota.

USDA Soil Conservation Service (SCS), St. Paul and Glenwood, Minnesota; and Plant Materials Center, Bismarck, North Dakota.

University of Minnesota (U of M) Pope County Extension Director; West Central Agricultural Experiment Station (WCES) at Morris, Minnesota; Minnesota Extension Service (MES); and the College of Natural Resources, Department of Forest Resources (FR).

This publication presents findings from the shrub-testing project conducted by these agencies. It provides farmers with research-based, alternative barriers to replace trees that were lost to center-pivot irrigation systems.

Herman Rosholt Research Farm

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The Herman Rosholt Research Farm (Figure 1) is in the Bonanza Valley of west central Minnesota, on the southwest edge of Westport, Minnesota, about 14 miles northeast of Glenwood, Minnesota, on Highway 28. Herman Rosholt, a retired farmer, donated this 40-acre tract of land to the Pope County SWCD for experimental purposes. Thirty acres of the Herman Rosholt Research Farm is tillable. Clinton Welte, Brooten, Minnesota, donated the single tower center-pivot irrigation system (Figure 2). The irrigation system has an effective coverage of about 6-1/4 acres.

Figure 1. Sign on Herman Rosholt Research Farm.

Figure 2. Single-tower center-pivot irrigation system on Herman Rosholt Research Farm.

The Pope County SWCD Board furnished the farming equipment used on the Herman Rosholt Research Farm. A local farmer operated the equipment and maintained the weed control in the shrub plots.

Planting Site

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The location of the one-acre, rectangular planting site on the Herman Rosholt Research Farm is in the center of the south edge of the effective irrigation coverage. The soil (Esterville) is a well-drained loamy sand with a moderately rapid permeability in the upper horizons and rapid permeability in the lower horizons. The soil horizons are mostly neutral to medium acid. Native vegetation was tall grass prairie. This soil is representative of 250,000 acres in the area now under irrigation. The site was in grass, primarily quackgrass, before planting preparation.

Agronomic Crops

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The original purpose for growing crops in the bays between the shrub rows was to determine the effect of crop fertilizer and chemical treatments on the shrub species. In 1979 (Figure 3), researchers grew Adzuki beans in the bays; and in 1980 (Figure 4), they grew wheat and barley. Unfortunately, budget restrictions prevented the planting of crops from 1981 through 1986. Soybeans were planted in 1987 and corn in 1988 and 1989.

Figure 3. Adzuki beans in 20-foot bays between shrub rows in 1979 — first year of study. Sign lists the order of species in the 24-foot-row plots.

Figure 4. Wheat and barley in 20-foot bays in 1980 — second year of study. Zabels honeysuckle seen in the foreground. The date of the photo is August 5, 1980 — the first field day.

Site Preparation and Weed Control

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The planting site was plowed and disked the fall of 1978. Failure to treat with Roundup (Glyphosate) before plowing and disking resulted in severe quackgrass competition for several years. Weed control following planting consisted of applications of Princep (Simazine) (granular or spray) in 1979 through 1981, Ronstar (Oxadiazon) in 1982 through 1984, Princep in 1985 and 1986, and Casoron (Dichlobenil) in 1987 through 1989. Some Roundup and rototilling was used every year.

Measurements and Evaluations

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Measurements and evaluations were performed at the end of each growing season for survival, vigor, height, spread, disease and insects, animal damage, and general suitability for use under center-pivot irrigation systems. The overall condition of each plant was rated as excellent, good, fair, poor, or very poor.

During the 1984 and 1985 growing seasons, almost all activities on the Herman Rosholt Research Farm ceased because of budget problems. This included a shutdown of the center-pivot irrigation system. Although the 1984-85 growing seasons were not exceptionally dry years, all shrub species showed symptoms of drought damage to varying degrees. In 1986, the Pope County SWCD Board led by Chairman Dave Jellum reinstated research activities and turned on the irrigation system for the shrub plots.

Shrub Species Tested

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The planting stock was provided by the Soil Conservation Service Plant Materials Center located at Bismarck, North Dakota. Most of the planting stock came from known seed sources. The original planting on May 1, 1979, included 16 shrub species and 2 tree species. When shrub species' performance demonstrated characteristics unfavorable for use in windbreaks under center-pivots, they were replanted with new species or varieties.

Table 1 lists the discontinued shrub species, in alphabetical order by planting date, reasons for discontinuing, date of removal, and replacement species.

Table 2 lists the final shrub species tested, in alphabetical order by planting date, and gives comments on their performance through the 1989 growing season when the project was terminated.

Conclusions

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After the October 2, 1989 measurements, there was mutual agreement that we had enough information to make valid recommendations as to which shrub species were desirable, showed promise, or were undesirable for use in single-row field windbreaks under center-pivot irrigation systems. Consequently, this project was terminated after 11 growing seasons. During this time, 2 tree species and 34 shrub species and varieties from 18 genera were tested.

By the fall of 1987, the 2 tree species and 17 shrub species and/or varieties had been eliminated from considered use in field windbreaks under center-pivot irrigation systems. Of the remaining 17 species still being tested by the fall 1989 termination date, 8 were eliminated from consideration because of unsatisfactory crown characteristics, root suckering, or generally poor performance.

Three species (European Cotoneaster, 'Rem Red' Honeysuckle, 'Cling-red' Honeysuckle) showed some promise, 1 species (Black Chokeberry, Figure 5) which performed well prior to shutting down the irrigation system should be considered, and 5 species (Figure 6) were recommended for planting under center-pivot irrigation systems in Minnesota: Persian Lilac, Chinese Lilac, Peking Cotoneaster, Glossy Buckthorn (also called Tall Hedge or Columnar Buckthorn), and Caragana. Except for Caragana which was planted in 1982, these were the only species left from the original 1979 planting. Although Arrowwood (planted in 1979) was eliminated after the 1984-85 irrigation shutdown (all but one plant perished in the drought), it should be added to the recommended list because of its excellent early performance (Figure 5) — we would not expect farmers to shut down their irrigation systems when crops were in need of water.

The reader should remember that the shrub species included in this study were under a center-pivot irrigation system on Esterville soils in west-central Minnesota. These species may perform differently on other soil types in other areas of Minnesota or in other states. However, this study can serve as a guide for recommendations on shrub species under center-pivot irrigation systems throughout Minnesota and in neighboring states and Canada.

Although the decision to shut down the center-pivot irrigation system during the 1984 and 1985 seasons was unfortunate, it did provide some valuable information. This shutdown demonstrated the drought tolerance of the species tested and how they adapted to soils having excessive internal drainage. This study did not determine the proper spacing for the species recommended for use in single-row field windbreaks under center-pivot irrigation systems.

A species crown spread helps specialists make a spacing determination. However, they should consider other factors.

Some farmers want a windbreak that (1) will filter the wind and provide air movement over crops during the growing season and (2) filter blowing, drifting snow to provide uniform snow distribution during the winter. For these farmers, the plants must be planted far enough apart so that the crowns will not touch — or planted closer together and every other plant removed before crowding occurs.

On June 6, 1991, the project was officially terminated when all shrubs were removed from the planting site.

Table 2. Final Shrub Species Tested at Project Termination Date, October 2, 1989 Back to Table of Contents / Back to Text

Recommended			Not Recommended
Species by Year of Planting			Comments
1979	Black Chokeberry		Good survival (88%). Performed very well first 5 years until 1984 when the irrigation system was shut down — exhibited sparse foliage ever since. Originally was one of the more promising species with its annual heavy fruit production, shiny-green leaves, and beautiful fall color. Some indication of root suckering. Could be recommended, but may not grow tall enough — other species are better choices.
	Peking Cotoneaster		Excellent survival (100%). All plants were in excellent condition. No ill effects from 1984-85 irrigation shutdown. Only Persian Lilac had more uniform height growth. Its width (7.5 feet) exceeded its height (6.5 feet) — a possible disadvantage. Highly recommended.
	Glossy Buckthorn		Good survival (81%). Its narrow crown (2.3 feet) in relation to its height of 4.9 feet makes this a desirable species. Somewhat irregular height growth — 4.5 feet difference between tallest and shortest plant. Suffered several years from 1984-85 irrigation shutdown but has come back so that now 85% of the plants are in good to excellent condition. Recommended, but could exceed height of traveling boom.
	Persian Lilac		Excellent survival (100%). Best performance of all species tested. All plants were in excellent condition. No ill effects from 1984-85 irrigation shutdown. Most uniform height growth of all species — only 1.3 feet difference between tallest and shortest plant. Its width (8.5 feet) exceeds its height (7.2 feet) — a possible disadvantage. Highly recommended.
1982	Caragana		Excellent survival (100%). All but one plant was in good to excellent condition. No ill effects from 1984-85 irrigation shutdown. Height growth (7.3 feet) far exceeds its width (4.3 feet) — a distinct advantage. Somewhat irregular height growth — 7 feet difference between tallest and shortest plant. Recommended, but could exceed height of traveling boom.
	Nanking Cherry		Fair survival (75%). Seventy-eight percent of plants were in good to excellent condition. As wide as it is tall at 4.9 feet. Showy whitish to pink flowers; edible fruit. Relatively short life is a disadvantage.
	Chinese Lilac		Fair survival (70%), but all live plants were in good to excellent condition. Width equals height. Appears to be equal to Persian Lilac in overall performance. Recommended.
Species planted in 1986 and later either showed no promise or had not been tested long enough to be ranked. Therefore, none of these species can be recommended.
1986	European Cotoneaster	Fair survival (69%), but 10 of 11 remaining plants were in good to excellent condition. Shows promise.
	'Scarlet' Mongolian Cherry	Poor survival (62%), but 8 of 10 remaining plants were in good to excellent condition. Prolific root-suckering is a disadvantage.
	Nannyberry	Poor survival (38%) from 1986 planting, but all remaining plants were in good to excellent condition. Of 10 plants replaced in the spring of 1989, one died and 4 were in good to excellent condition. Based on growth of wild plants in Minnesota, it will eventually exceed height of traveling boom.
1987	False Indigo	Good survival (88%). All remaining 14 plants were in good to excellent condition. After three growing seasons, its width of 5.5 feet exceeds its height of 4.2 feet. Considerable "layering."* Sprawling form subjects this species to snow damage. Not recommended.
		*"Layering": any portion of an attached branch taking root where it comes in contact with the soil.
	Amur Honeysuckle	Poor survival (50%) and only 3 of 8 remaining plants were in good to excellent condition. After three growing seasons, only 1.5 feet in height — width exceeds height. No evidence of aphids. Appears to be susceptible to powdery mildew. Early performance does not warrant a recommendation.
	'Rem Red' Honeysuckle	Very poor survival (19%) from original 1987 planting, but 3 remaining plants were in good to excellent condition. Width exceeds height by 1.6 feet. Ninety-two percent survival in 1989 replacement planting and 10 of 12 plants were in good to excellent condition. No evidence of aphids. Ultimate width in relation to height may determine its potential. Early performance indicates some potential.
1988	'Hedgeking' Honeysuckle	Fair survival (69%) from original 1987 planting, and only 7 of 11 remaining plants were in good to excellent condition. In spring, 1989, 5 replacements were planted, 4 survived, but only 1 was in excellent condition. No evidence of aphids. Generally poor performance. Not recommended.
1989	Meadowlark Forsythia	After only one growing season, 88% survival, and 50% of live plants were in good to excellent condition. Early performance does not warrant a recommendation.
	'Freedom' Honeysuckle	After only one growing season, only 69% survival, and 9 of 11 remaining plants were in good to excellent condition. No evidence of aphids. Reported to have leggy, open growth — not a good characteristic for use in windbreaks under center-pivots or in farmstead shelterbelts.
	'Cling-red' Amur Honeysuckle	After only one growing season, 100% survival, and all plants were in good to excellent condition. No evidence of aphids. Early performance indicates some potential.

References

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Sorenson, Doug. 1981. Wisconsin Center Pivots and Breaks Go Together to Curb Erosion. Irrigation Age, October 1981.

Sperbeck, Jack and D'Silva, Emmanuel. 1978. Science Strives to Make Irrigation More Efficient. Minnesota Science, Vol. 33, Winter 1978, pp 8–9. University of Minnesota, Agricultural Experiment Station.

Widdel, Keith H. 1981. Shrubs and Grasses Save Soil and Crops on Irrigated Fields. Soil and Water Conservation News, December 1981, p. 7.

¹From a conversation with Jerry Wright, Minnesota Extension Service irrigation specialist, West Central Experiment Station, Morris, Minnesota.   (Back to footnote 1 source)

²Ibid.   (Back to footnote 2 source)

Acknowledgments

The authors are grateful to the University of Minnesota (U of M) Agricultural Experiment Station (AES), Minnesota Extension Service (MES), the Department of Forest Resources (FR), and the USDA Soil Conservation Service (SCS), St. Paul, for their cooperation throughout the study. The authors are especially indebted to the local Bonanza Valley irrigators (farmers) for instigating and encouraging the study; the Pope County Soil and Water Conservation District (SWCD) for providing the test sites; and the USDA SCS, Plant Materials Center, Bismarck, North Dakota, for providing most of the plant materials.

Organizing and conducting this study required the assistance of many individuals. The authors wish to express their appreciation to the following key individuals for their contributions: John Hultgren, Woodland Conservationist (retired), USDA SCS, and Jerry Wright, Extension Agricultural Engineer, U of M, who were the prime instigators in initiating this study; John Morris, Pope County Extension Agent and Director, U of M, and Wesley Gray, Horticulturist, West Central (WC) AES, U of M, who were among the original planners, assisted with the original planting, and continued to actively support the project; Fred Bergsrud, Agricultural Engineer, U of M, who chaired the "Westport Committee (composed of members from organizations involved in research on the Rosholt Farm) and whose efforts were influential in the continuance and/or resumption of research activities; Cindy Buschena, Junior Scientist, Department of FR, U of M, who helped with the planting, early weed control, and conducted the measurements during the early years of the project; Richard Vatthauer, Superintendent, and Steven Poppe, Research Plot Coordinator, WCAES, U of M, who, respectively, furnished and operated weed control equipment during the 2–3 years that the Experimental Farm was without equipment and a caretaker; George "Larry" Pollard, Biologist, and Robert Blackbourn, Forester (retired), USDA SCS, who assisted with replacement plantings and annual measurements, and who were ardent supporters of the project; John Koosman, Pope County Conservation Technician (retired), USDA SCS, and Kim Krueger, Pope County SWCD District Technician, who were an integral part of the project and were involved in all project activities from its initiation through its termination; David Jellum, Chairman, Pope County SWCD Board, and all Board members who, in spite of several years of U of M budgetary restraints, were responsible for resuming activities involving the irrigating of shrub plots; Peter Gilbertson, a local farmer who maintained weed control in the plots; and finally the authors are especially grateful to Mary Ann Hellman, Principal Secretary, Forest Resources Extension, U of M, for her patience and expertise in the preparation of the text and tables of this publication.

Harold Scholten Extension Windbreak/Shelterbelt Specialist Department of Forest Resources College of Natural Resources University of Minnesota St. Paul, Minnesota	David D. Breitbach Conservation Agronomist USDA Soil Conservation Service St. Paul, Minnesota
Russell J. Haas Plant Materials Specialist USDA Soil Conservation Service Bismarck, North Dakota	Erling T. Jacobson Plant Materials Specialist USDA Soil Conservation Service Midwest National Technical Center Lincoln, Nebraska

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