Volume 78 Article 5

1-1-1991 An Project: Sustainable -Shrub- Grass Buffer Strips Along Waterways Richard Schultz Iowa State University

Joe Colletti Iowa State University

Carl Mize Iowa State University

Andy Skadberg Iowa State University

Bruce Menzel Iowa State University

Follow this and additional works at: https://lib.dr.iastate.edu/amesforester Part of the Sciences Commons

Recommended Citation Schultz, Richard; Colletti, Joe; Mize, Carl; Skadberg, Andy; and Menzel, Bruce (1991) "An Agroforestry Project: Sustainable Tree- Shrub-Grass Buffer Strips Along Waterways," Ames : Vol. 78 , Article 5. Available at: https://lib.dr.iastate.edu/amesforester/vol78/iss1/5

This Article is brought to you for free and open access by the Journals at Iowa State University Digital Repository. It has been accepted for inclusion in Ames Forester by an authorized editor of Iowa State University Digital Repository. For more information, please contact [email protected]. AN AGROFORESTRY PROJECT: susTAINABLE TREE-SHFIUB-GRASS BUFFEFI STRIPS ALONG WATERWAYS

BY

F]lCHAF]D SCHULTZ, JOE COLLETTl, CAFZL MIZE, ANDY SKADBEFIG, AND BFIUCE MENZEL

Introduction the streambank, the aquatic , and for providing for terrestrial Iowa is a mosaic landscape of agricultural . , pasture lands, native woodlands. prai- rie remnants, wetlands, and a network of A cooperative project on a private farm was streams and rivers. With settlement and the started in the spring of 1990. An interdiscipli- increased mecha- naryteam fromthe nization of agricul- Departments of ture, many natural , a as ` sgffi se.>< isee`s±gg // //,i/// i/// i/ // // //////i1/,,,,,74,i,,;,,#,// ,z/ /// Agronomy, Geol- woodland corri- `x,`,`/`se*/a <.*ng ng`'` -i- dors along these `asJz '3¥sezl , ` i ogy and Atmo- i // /// streams and rivers spheric Sciences, i$3& and Ecol- were removed. ``z`as,se:xtx:"z/7Zy///`^assse Present farming ogy at Iowa State :.,=.:`.:,` practices have re- -+;asREl'`:*` -``' fu .., `>..RTRE University have sulted in: in- established a ri- creased loss of parian buffer strip soils, which dimin- located on the Ro- ishes soil fenility, nald Risdalfarmon es,: and increased use Bear Creek nonh of agri-chemicals, of Ftoland, Iowa. which threatens the quality of water. Today's The site was intensively grazed and used for concerns about soil loss and ground and many years as a tractor access to nearby contamination must be ad- fields. Flow crops were planted close to the dressed by both the agricultural and non- creek along about 1/4 of its length and within agricultural communities of our state. 1 to 3 chains along the rest. The project includesfast-growing bottomland hardwoods, Tree, shrub, and grass covered llriparian" highquality hardwoods, aswell asshrubs and buffer strips can contribute to sustainable switchgrass. by reducing soil loss, improving waterquality, and stabilizing the banks of the Iowa Agriculture and Non-point Source drainage system. The is land Pollution that borders the banks of streams or lakes where vegetative communities consist of Although governmental action to reduce point plantsthat have systems in close proxim- sourcewaterpollution hasalong history inthe ity to the watertable. Such communities may United States, The Federal Water Pollution consume substantial amounts of water, but Control Act (PL 92-50O) of 1972 was the first more importantly are necessaryforprotecting national legislation to recognize the problem

1991 Ames Forester of non-point source (NPS) pollution. The act water systems. had two primary goals: 1 ) to maintain surface sufficient to support specific The Iowa landscape is dynamically uses such as drinking, general recreation, imbalanced because of the loss of diverse, and fishing, and 2) to restore and maintain the non-agricultural - , prai- physical, chemical, and biological integrity of ries, and wetlands. For example, lowa's waterways. The approach to NPS pollution forest cover has been reduced from about reduction has been to develop Best Manage- 19o/o ofthe state to 4%, and native prairie and ment Practices (BMP's) on watershedswhere wetlands have been reduced by over 99o/o there is substantial potential for movement of (ThomsonandHertel,1981 ;Smith,1981 ;and pollutants to drainageways. Until recently, Bishop,1981). These losses result in a re- recommended BMP'sforagricultural landhave duction in the assimilation capability of the chiefly involved application of soil landscape, and a loss of wildlife habitat. By control treatments, e.g. terracing, grass wa- reintroducing ecosystems of permanent terways, and minimum tillage. Actual experi- in sensitive locations on the land- ence with such BMP's, however, has shown scape, soil losses will be reduced and envi- that they are rarely adequate to deal with the ronmental conditions improvedo The intro- pervasiveoverlandandsubsurface movement duction of diverse buffer strips along many of agricultural poIIutants. Substantial quanti- streams using fast-growing , shrubs, and ties ofsediment andchemicals still maketheir perennial crops would reintroduce some of way into the bottomlands along creeks, these dynamic interactions while producing streams, ponds, and lakes. These problems profitable alternative crops for farmers. The are fuhher aggravated when modern, typical potential environmental benefitsofbufferstrips Iowa row farming is practiced down to are to keep surface on the site the edge of creeks and waterways. where they are generated, to improve water quality by filtering out the nutrients and lt is now clear that innovative approaches chemicals associated with agricultural pro- mustbedevisedto reduce movementofthese duction, to increase streambank stability and pollutants (soil and agricultural chemicals - improvethe in-stream environment, to provide nitrogen and ) into waterways. wildlife habitat, to provide carbon storage to Moreover, these new approaches must be reduce greenhouse warming, and to provide implemented on awatershed scaleto achieve alternative income for the landowner. significant improvements in water quality. Tree, Shrub, and Grass Buffer Strips as Iowa agriculture can be characterized as BMP's for the Riparian Zone fence-row-to-fence-row, highly mechanized, and chemically dependent (Jensen,1988). The riparian zone of a stream is the last area Continued production may lead to reduced forintercepting and processing up-hill materi- soil productivityand surface andgroundwater als produced by agricultural practices before quality because of soil erosion and percola- they enter the stream (see figure 1 ). One of tion of chemicals. Soil and farm chemical the best management techniques for the ri- movement from agricultural fields has re- parian zone is to maintain a continuous cover sulted in environmental problems that need crop that has an extensive and dynamic root immediate attentl'on. To maintain a sustain- system. Such asystem iscapable ofprocess- able agricultural system, erosion losses must ing large quantities of water and associated be reduced on-site, and losses that inadvert- agricultural chemicals, while also trapping entlyoccur must be stopped beforethey enter sediments moving from adjacent crop fields.

15 Trees and grasses, often the natural ecosys- or burned. Compared with annual crops, this tem that was cleared from the riparian zone, carbon storage is long term. Such long-term provide such a crop. Fast-growing trees can storage reduces carbon dioxide in the air, be managed to provide the benefits of a thus reducing the greenhouse effect. When permanent covercrop while also providing an the trees are utilized for energy through gas- economically sustained yield of for ification, combustion, or use in a processed energy production or h-lgh quality timber, if liquid form, the carbon dioxide that is addedto species such as walnut and oak are included. the atmosphere is not carbon that has been in extremely long-term storage, as is the case Tree buffer strips improve the in-Stream envi- with fossil fuels (e.g., coal and oil). Also, the ronment and provide wildlife habitat, as well released carbon dioxide is quickly removed as an aesthetically pleasing diversity in the from the air by the resprouting shoots. Thus, landscape (Kennedy,1977). Whereas tree a 6tbalanced," closed cycle of carbon genera- buffer strips process surface and subsurface tion and use is established. water and associated chemicals, they also stabilize stream banks that otherwise con- Integrating Short-Rotation Woody Crops tinually erode into highly productivecropfields. into a Buffer Str'lp Agroforestry System Trees are able to reduce the rate Of Stream bankcollapse because theirpermanent Agroforestry, the practice Of integrating trees extend into the soil, and their stems provide with agricultural crops and livestock in space increasedfrictional surface during flood flows. and time, has been used in tropical countries Additionally, trees reduce in-Stream for decades. Growing trees in conjunction load and water temperatures while providing with agricultural crops and livestock can di- organicdebristhatis afood sourceforbenthic versify farm income by producing a wider organisms (Swanson et al., 1982). range of market and non-market products from the same land unit and aid in soil and Mixtures of trees, shrubs, and grasses Pro- waterconservation (Betters,1988). There is vide good habitat for wildlife, which may be a need to develop projects in other agro- desired by the landowner and the public. ecological conditions (e.g., the temperate Most of lowa's forests, prairies, and WetlandS Nonh Central F]egion of the U. S.) to test the were cleared for agricultural purposes. What viability of the system (Ssekabembe, 1985). is left, forthe mostpan, are small, fragmented, and isolated ecosystems. Movementofwildlife The use of, shon rotation woody Crops and between these systems is difficult because of herbaceous crops in adjacent strips within a the wide open crop spaces that provide little buffer strip system is an agroforestry applica- cover. The use of mixed tree-shrub-grass lion that can be used to reduce the negative buffer strips along streams can provide corri- environmental impacts from current agricul- dors of cover and habitat for wildlife move- tural practices. This system intercepts both ment. The use of a variety of vegetation also wind-and water-eroded soil, as well as agri- provides diversity for wildlife use. cultural chemicals moving from crop fields. Potential groundwater pollutantS may be Se- The same buffer strips also SequeSter large questered into the standing biomass (Licht quantities of carbon dioxide that should help and Schnoor, 1989). The system also estab- stabilize the global warming phenomenon. lishes corridors of diverse vegetation provid- For example, is about 50% carbon. ing food for wildlife and avenues for move- This carbon is stored in the Stems Of trees in ment by maintainingvisual andthermalcover. the until the wood is decomposed

1991 Ames Forester The problem with Iowa riparian zones is that Project Hypothesis they have been abused, which has led to accelerated erosion and contamination of The hypothesis that is being tested in this surface and groundwaters. Continuously proJ'ect iS that the buffer-Strip System Will trap vegetated buffer strips could reduce these soil that is eroding from the row cropped adverse effects. The shon-rotation-woody- uplands and process contaminated subsur- crop-prairiegrassagroforestrysystem meets facewatercarrying agriculturalchemicalsthat the criteriaforpermanentcoverwith excellent are moving into the alluvial zone. Further, it is water processing qualities. Atthe same time, expected that the buffer strip can provide the system provides tangible, economic, en- periodic to annual economic returns to the vironmental, and social benefits for Iowa land farmer in the form of harvested biomass that owners and citizens. can be used for on-farm energy. The buffer strip also is expected to provide increased Criteria for establishing buffer strips must be wildlife habitatl especially because of the di- developed to evaluate theirphysI'Cal, enVirOn- versity of being used. From a global mental, and economic ,productivity. On-farm perspective the buffer strip is expected to demonstrations must be established to show provide long-term carbon storage to reduce landowners how buffer strl®ps function. the greenhouse effect.

The Risdal Buffer Strip Project An interdisciplinary team of researchers is intensively monitoringthe sitetotestthe above This cooperative project was initiated in the hypothesis. The team consists of specialists spring of 1990. Mr. F}onald F}isdal, a farmer in forage crops, soils, groundwater, forest from Poland, Iowa, was interested in applying hydrology, , forest economics, some BMP's on his stretch of Bear Creek to biometrics, and landscape ecology. reduce NPS pollution, improve wildlife habi- tat, and provide opportunities for additional The research will provide base-line data on on-farm benefits from woody biomass. This costs, biomass production, carbon storage, project is supported by funding from the environmental impacts, net energy output, Leopold Center for Sustainable Agriculture and the effect of tree-shrub-grass buffer cor- and EPA 319 funds for NPS control. ridors on riparian zones. The project provides a demonstration of buffer strips to farmers The Bear Creek watershed is about 17,700 and regulatory agencies. lt represents a acres (7160 ha). lt is located in Story County coordinated effon by a landowner and gov- in the hean of predominantly agn'culturaI land. ernmental bodiesto evaluatetree bufferstrips This watershed is drained by Bear Creek, as an innovative and sustainable agricultural which flows for 22 miles (34.8 km) before it practice, which should actively negate the empties intothe skunk River. BearCreek has environmental impactsfrom up-hill soil erosion over 17 miles (27.8 km) of major tn'butaries, and non-point source agriculture chemicals which drain undulating to level topography. while providing economic alternatives for the Most of the area was originally covered with farmer. prairievegetation, exceptforforestsalongthe lower end of the creek. The major soils were Project Objectives: formed in glacialtill orfrom local alluvium from till. The soils range from well-drained to 1. To measure the changes in quality and poorly drained. quantity of surface water and groundwater moving from up-slopethroughthe mixedtree-

17 shrub-grass buffer strip to the stream. sisted of: 1) a poplar hybrid that has been tested extensively and is readily available in 2. To measure the quantity Of uP-Slope Sedi- Iowa, 2) green ash and, 3) mixed plots of four ment that is intercepted by the buffer strip. rows of silver maple with acenter row of black walnut. Two rows of shrubs, planted with 3. To measure changes in Soil and three feet between shrubs and six feet be- nutrients to determine their role in chemical tween rows, are planted upslope from the uptake from water moving through the buffer trees. All plots contain one row Of red-OSier strip. dogwood and one row of ninebark. Finally, a 24 ft wide strip of SWitCh grass iS Planted 4. To measure the effect Of the buffer Strip On upslope from the shrubs. stream bank stability and in-stream environ- ments. The plots are identified by their position and tree species makeup. Each species is found 5. To determine the impact Of the buffer Strips in one ofthe three creek location plots. There on wildlife populations. are three replications of each tree species for most purposes of the project. However, to 6. To determine the biomaSS and POtential observe the effect of the trees on channel energy productivity of the buffer strip. stability there is only one plot per species. lt was assumed that, for bank stability pur- 7. To determine the economic COStS and ben- poses, the species had lessto do with stability efits of the buffer strips. than the fact that there were trees. lf that assumption is correct, then there are three Location and Study Design replications of trees by creek locations. One of the keys to understanding the effect of the This project is being done On a farm located buffer strip influence on bank stability is to 1.5 miles north and 0.5 miles east of F}oland, determine the dynamics of the root systems. Iowa. The farm is an 80 acre tract through From work with root systems in Other Studies, which Bear Creek, a major tributary Of the we believe that for these species the soil northern reaches of Skunk F}iver, passes. texture and structure have more i,nfluence on Bear Creek meanders through the Risdal rootingcharacteristicsthanthespecies. These farm fora length ofabout3,OOOfeet (3/5 mile). assumptions will be tested during the study. The length ofthe creekwas broken into 280 ft long plots extending along both Sides Of the Because much of the area Was in Pasture creek (see figure 2). Plots were identified by when it was converted to buffer strip plots, it their location along the creek as being: a) was thought that the controls should be left in inside bend, b) outside bend, or c) straight the pasture grasses and any areas that had reaches of the creek. A total of 15 plots were been cultivatedtotheedge ofthecreekshould defined. Several areas were not used be- also be planted to a mix of pasture grasses. causetheyweretoo small orthere was debris The site was prepared by aPPIy'lng a general that could not be cleared from the site. purpose herbicide in strips where the rows of trees and shrubswere planted, and bydiscing Three combinations oftree-Shrub-grass PIots the area to be planted with switchgrass. One were established. Each plot consists of five year-oldtreeandshrubseedlingswere planted rows of trees planted closest and parallel to and the switchgrass was planted with a drill. the creekwith fourfeet between trees and six All of the plots were planted during the spring feet between rows. The tree plantings con- of 1990. Additionally; about seventy-five fast

1991 Ames Forester growing willow were planted on a sand bar. First Year Results

Growth and yield data for the trees and Planting the entire design took a little more switchgrass from permanent inventory plots than one day (May 12,1990). About 10 will be collected. Annual biomass yield, car- people spent close to 100 hours planting with bon content, and BTU energycontents will be atractorand planter, and by shovel and auger calculated. The trees will be grown on a 4-8 where it was impossible to get a tractor close yearrotationdepending onspeciesandgrowth enough to the edge of Bear Creek. The rates. Black walnut will be grown on a 45-55 following numbers of plants were planted: 1 ) year rotation. 1,200 green ash; 2) 1,200 poplar hybrids; 3) 800 silver maple; 4) 400 black walnut; and 5) Soils on the site will be characterized by a 900 each of ninebarkand red-osierdogwood. grid-based survey. This informa- It was a great year for because lion will be compared to that described in the itstayeddryjust long enough forplantingto be Story County Soil Survey (DeWitt, 1984). completed. Following planting, it rained Detailed laboratory characterization of the probably too much foroptimal growth. On the soil will be done (particle size distribution; other hand, after three years of drought, this total N; total P; organic C; pH; bulk density of was a pleasant change for the trees. key horizons; water retention characteristics of key horizons; and free Fe and Mn oxides). Weeds were controlled by mowing the area Because water quality is an impohant part of between the tree and shrub rows. Because of the project, a series of sampling devices will our desire to reduce chemical inputs into this be installed. Changes in waterquality moving buffer strip system, we did not want to elimi- through the unsaturated zone from up-slope mate ground cover through mechanical or through the the buffer strip will be measured. chemical cultivation, thus exposing the bare Annual soil samples will be tested for major soil to potential water erosion. This approach cation and anion concentrations and the pes- may reduce growth somewhat, but it will help ticides alachlor, atrazine, and bladex. to maintain the primary function of the buffer Hydrogeological investigations will be made strip as a system designed to reduce NPS to: 1 ) determinethe groundwaterflow system pollution. near the creek, 2) quantify the amount of groundwater moving into the creek, 3) deter- All permanent inventory plots were installed. minethe ambientgroundwaterchemistry, and Survival of all plants was excellent, except for 4) determinethe effectofthe riparian plantings the red-osier dogwood which will probably be on groundwater flow and chemistry. replanted during the spn'ng of 1991. Prelimi- nary survival data are given in table 1. The costs associated with site preparation, planting, and management activities will be A major flood on June 17, 1990, washed out determined. A break-even analysis will be the bridge that crossed the creek and washed done to determine the biomass production out partial rows of trees on several plots. that would be required annually when valued MaJ'OrCOllaPSeS along the bank also occurred at a given price, to off-set the costs of site and in at least one location some of the preparation, planting, and management. A planted trees collapsed into the creek and thorough benefit-cost analysis will be con- were washed away. The planting of the ducted as data of the benefits of the buffer switchgrass was delayed and washed out in strip, relating to a reduction in soil erosion and several locations. All but one area of switch- pollution, are determined. grass has now been replanted and should be

19 well established during 1991. The switch- system established. We were held up from grass was planted later than desired, again doing the soil, geological, and hydrOIOgiCal because of the wet conditions. As a result, it work for several reasons. The emphasis for is not astall as it might have been under more the second yearwill be to complete the instal- llnormaI" years. lation of monitoring wellsand lySimeterS, Creek cross-sectional profile markers, sediment Because of the high rainfall and Subsequent traps, the weather station, and flow monitor- wet conditions following planting, the soil de- ing andwatersampling equipment, if itcan be scription, surface and groundwater monitor- purchased. Chemical analysis will get in full ing equipment installation has not been com- swing and growth parameters will continue. Dead plants will be replaced in the SPr'lng pleted. Eightwells have been installed. About twenty more wells may be needed. including a major replanting of red-osier dog- wood. Some additional willow may be Planted Summary along the stream bank to test their ability to quicklydevelop roots and hold a bankin place The pastyearwas one Primarily ofgetting the before the buffer strip becomes established.

Table 1. Overall means after one growing Season for buffer Strip woody Plants

Species (n) Height (cm) Diameter (mm) Mortality (a/a) LO=®tt-S Green Ash (114) ES?3l ®®O)®qT-.CQap Poplar Hybrid (104) Silver Maple (93) Black Walnut (23) Ninebark fled-osier Dogwood

The higher mortality Of the POPlar hybrid Stems from One Plot Where flood waters actually tore trees out of the ground.

1991 Ames Forester 21 Outside silvermaple-I]II]t E black walnut (275')

I Inside plIIt T control Straight (250l) - control I]Itlt I 5 (300') []lDt 6

ln_sit_e_I I Straight control Grafted walnut -silver maple silver maple - - Christmas trees black walnut (300') Outside plt]t 14 / green ash (270') I]II]t 5

Outside Inside control poplar F]Iot 4 -N (300') (300') plut l3 / unused (l80') Straight Layout of plots at Risdal Farm poplar - Bridge (280') / Not drawn to a scale IIIot l2 Outside Shows general lns'lde p(8opdq)r pIDt i location of plots green ash (270') lIIot ll Plots have 5 rows of trees planted parallel to creek with 4' between trees and 6' between Inside rows, then 2 rows of shrubs Outside sgYae:kmwaapllneu-t p ID I 2 planted 3l between plants and control 6' bet\^,een rows, then 24' of (320') (275') switch, All together they form a band 66' widel I|Int lH /

Control plots were planted to Straight Straight a mix of grass seed if not control gre(2e7nOq)Sh F]lOt 1 already in pasture plIIt I (300')

Figure 2. Layout of plots at Risdal Farm

1991 Ames Forester Literature Cited Ssekabembe, C.K. 1985. Perspectives on hedgerow intercropping. Agroforestry Sys- Betters, D.F3. 1988. PIanning optimal eco- tems 3:339-356. nomic strategies for agroforestry systems. Agroforestry Systems 7:17-31. Thomson, G.W. and H.G. HerteI.1981. The Bishop, Ft.A.1981. Iowa's wetlands. Proc. forest resources of Iowa in 1980. Proc. Iowa Iowa Acad. Sci. 88:ll -16. Acad. Sci. 88:2-6.

DeWitt, T.T. 1984. Soil survey of Story County, Iowa. USDA Soil Conservation Ser- vice-

Jensen, H.M.1988. Acceptingthechallenge. J. of Freshwater. ll :2

Kennedy, C.E. 1977. Wildlife conflicts in riparian management: water. ln: F3.F3. John- son and D.A. Jones, ed. Importance, preser- vation and management of riparian habitat. USDA For. Serv. Gen. Tech. Report F}M-43. pp 52-58.

Licht, L.A. and J.L. Schnoor. 1989. Poplar tree buffer strips grown in riparian zones for biomass production and non-point source pollution control. Final F}eporfto The Leopold CenterforSustainableAgriculture, Iowa State U-niversity, Ames, Iowa, 50011.

PIatts, W.S. and 12 others. 1987. Methods for evaluating riparian with applica- tions to management. USDA For. Serv. Gen. Tech. Report lNT-221.

Smith, G.A. and nine others. 1987. Evalua- tion of sweet sorghum for fermentable sugar production. Crop Sci. 27:788.

Swanson, F.J., S.V. Gregory,J.F}. Sedell, and A.G. Campbell.1982. Land-water interac- tions: the riparian zone. Jn: R.L. Edmonds, ed. Analysis of coniferous forest ecosystems in the western United States. Hutchinson Floss Publishing Co. Stroudsburg, Penn. 419 PP.

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