DOT Project Number:  90-00-LRTF-403

Fiscal Year:  2004

Award:  $20,828.00

Principal Investigator:  Dr. Mahdi Al-Kaisi, Assistant Professor, Department of Agronomy, Iowa State University, malkaisi@iastate.edu

Other Project Participants:  Mark A. Licht, Extension Program Specialist, Iowa State University

Research Report:

INFILTRATION RATES FOR NATIVE AND RECONSTRUCTED PRAIRIES ACROSS IOWA

ABSTRACT
The objective of this project is to determine soil infiltration rates and soil bulk density under various species of grassy vegetation over different soil types in central and south central Iowa. The Story County sites included three roadside reconstructed prairies along Interstate 35. Additionally, a nearby rest area (with smooth bromegrass and bluegrass stands) and the Ames High Prairie State Preserve were used as comparison sites. The Jasper-Warren County sites included three reconstructed prairies and one roadside reconstructed prairie within the Neal Smith National Wildlife Refuge. An adjacent row crop site and Rolling Thunder Prairie were used as a comparison sites. Soil texture was loam for the Story County sites and silty clay loam for the Jasper-Warren County sites. First year data shows no correlation between establishment date and water infiltration rate or bulk density. Overall, water infiltration at the Story County sites ranged from 0.08 to 0.32 cm min-1 (0.03 to 0.12 inch min-1). At the Jasper-Warren County sites the overall water infiltration rates ranged from 0.06 to 0.28 cm min-1 (0.02 to 0.11 inch min-1). There was high variability within sites partially due to extremely wet weather conditions. The natural soil physical properties of the roadside soils have been compromised and no longer possess their natural condition. Significant improvement in soil physical and structural properties may take a longer time period and the establishment of a wide range of plant species.

INTRODUCTION
European migration into the mid-continent plains of the North America marked the demise of large prairie expanses. Most immigrants were interested in the economic potential inherent in the prairie while very few were interested in other aspects of the prairie environment. A small number of people have championed the need to preserve the rare remaining prairie remnants during the last 150 years (Conrad and Hess, 1998), but wide spread public interest in the environmental quality and the preservation of habitat and unique ecosystems did not occur until the effects of DDT and other chemicals in the environment came to the nations attention (Carlson, 1962). A multitude of entities have since been involved with preserving remaining prairie remnants or restoring and reconstructing prairies. Prairie reconstructions and restorations serve a wide range of purposes including: improving soil and water quality, weed control, preserving genetic resources, wildlife habitat, and social values (Thompson, 1992). The objectives of this study was to establish a data-base of bulk density and infiltration measurements on restored prairies and reconstructed sites of roadsides and compare them with adjacent cropland and native prairies.

MATERIALS AND METHODS
Description of study area:
This study was conducted in Story, Jasper, and Warren Counties in Iowa during 2004. The Story County sites were located along Interstate 35 (I-35) and at the Ames High Prairie Preserve. They are classified as typic Udorthents and typic Hapludoll, respectively (Table 1). The soils in Story County were formed in glacial till under native prairie vegetation (Dewitt, 1978). The I-35 roadside sites are on engineered soils. Engineered soils have been drastically altered by: excavation, additions of specific fill materials, dewatering, repeated vigorous compaction, and other construction techniques (Schroeder et al., 2004).

The prairie reconstruction sites within Neal Smith National Wildlife Refuge in Jasper County included Mahaska, Tama, and Otley soils which are classified as aquic Argiudolls, typic Argiudolls, and typic Argiudolls, respectively (Table 1). The Rolling Thunder native prairie is located in Warren County was located on a Sharpsburg soil classified as typic Argiudolls (Table 1). The soils in both Jasper and Warren Counties formed in loess under a native vegetation of tall prairie grasses (Bryant and Woster, 1978; Nestrud and Woster, 1979).

Experimental Design
In each site four completely randomized plots were selected at each treatment consisting of an area with a known planting history, suite of plants species, and management strategy (Table 1). The Story County sites consisted of roadside reconstructed prairie, bluegrass, bromegrass, and native prairie. The Jasper-Warren County sites consisted of roadside reconstructed prairie, reconstructed prairie, native prairie, and corn-soybean. Four replications (approximately 40 feet apart in an approximate square) of bulk density, 0-15 cm (0-6 in) depth and water infiltration were conducted at each replication. GPS coordinates were also recorded each point of measurement of bulk density and infiltration rate. One plant inventory was completed for each site encompassing all replications.

Measurements and Analysis
Infiltration rate was measured using a Cornell Infiltrometer (Ogden et al., 1997). This system consisted of a portable rainfall simulator placed on a single 24.1 cm (9.5 inch) inner diameter ring inserted 7 cm (2.8 inch) into the soil. The ring is equipped with an overflow tube to determine the time to runoff and runoff rate (Fig. 1). Rainfall simulator rates of 0.4 – 0.5 cm min-1 (0.16 – 0.20 inch min-1) were used. Bulk density samples were collected using a 1.85 cm (0.733 inch) diameter soil probe. For each replication 8 sub-samples were collected. The uppermost 1.3 cm (0.5 inch) soil was removed from the top and discarded. An additional 12.7 cm (5.0 inch) of the core was cut from the top and collected for bulk density determination. Each sample was oven dried at 105 ºC (221oF) for 24 hours and weighed. Bulk density was calculated with the formula;
BD = ODW/V,
Where; BD is bulk density, ODW is soil oven dry weight, and V is soil volume based on soil core of 1.85 cm (0.73 inch) diameter and 12.7 cm (5.0 inch) long. Site coordinates were determined by a Transplant IGPSJ unit with external antenna (Table 2).

RESULTS AND DISCUSSION
At both the Story County and Jasper-Warren County sites there is no correlation between establishment date and water infiltration rate or bulk density (Table 3). Overall, water infiltration at the Story County sites ranged from 0.08 to 0.32 cm min-1 (0.01 to 0.13 inch min-1). The bluegrass treatment that was established in the 1970 had the highest water infiltration rate of 0.32 cm min-1 (0.13 inch min-1) while the roadside reconstructed prairies had infiltration rates below 0.21 cm min-1 (0.08 inch min-1) (Fig. 1). At the Jasper-Warren County sites the overall water infiltration rates ranged from 0.06 to 0.28 cm min-1 (0.02 to 0.11 inch min-1) (Fig. 2). The row crop land and 1998 reconstructed prairie had the lowest infiltration rates (0.06 and 0.11 cm min-1 [0.02 to 0.04 inch min-1]), respectively) compared to the 1993 reconstructed, 2003 reconstructed, and 1998 roadside reconstructed prairies (0.29, 0.25, and 0.28 cm min-1 [0.11, 0.10, and 0.11 inch min-1], respectively).

All soil bulk densities were lower than 1.35 g cm-3 (84.2 lb ft-3) for both the Story County and Jasper-Warren County sites (Table 3). Bulk densities at the Story County sites ranged from 1.03 to 1.27 g cm-3 (64.3 to 79.2 lb ft-3) and bulk densities at the Jasper-Warren County sites ranged from 0.83 to 1.17 g cm-3 (51.8 to 73.0 lb ft-3). Additionally, at both sites for all treatments there was no correlation between bulk density and water infiltration rates.

CONCLUSIONS
In conclusion at the Story County sites, bluegrass and bromegrass generally improved water infiltration rates as compared to roadside reconstructed prairies. Water infiltration rates for the reconstructed roadside prairies were typically quite variable. At the Jasper-Warren County sites there was no trend established and the treatments were highly variable. At both sites the variability could not be explained by the bulk density, however the plant suites also varied widely by treatment. The prairie remnants displayed the most diverse plant populations followed by the reconstructed prairies. Roadside reconstructed prairies in general were less diverse than reconstructed prairies, while the monoculture grass species and row-crop fields displayed no plant species diversity (Tables 4, 5, and 6). Additionally, all of the roadside reconstructed sites were established on engineered soils. Engineered soils are drastically altered by excavation, additions of specific fill materials, dewatering, repeated vigorous compaction, or other construction techniques (Schroeder et al., 2004). The natural soil physical properties of roadside soils have been compromised and no longer possess the natural condition. Redevelopment of significant soil structure may take a longer time period and the establishment of a wide range of plant species.

Soil hydrological properties can be affected and vary with time, landscape position, and land management (van Es et al., 1999; Drohan et al., 2003; Lin et al., 1999). Investigation and evaluation of both soil infiltration and bulk density need to continue to develop a database that reflects a trend of both spatial and temporal effects of different grass mixes and management on soil infiltration rates and bulk density of newly reconstructed soils as well as agricultural and natural prairie soils.

ACKNOWLEDGEMENTS
We would like to thank Jim Priebe, David Youngblood, and the Warren County Conservation Board for allowing us access to Rolling Thunder Prairie and providing a plant inventory. We thank Erv Klass and The Nature Conservancy for allowing us access and providing the plant inventory for the Ames High Prairie State Preserve. We express our thanks and appreciation to Pauline Drobney and the Neal Smith National Wildlife Refuge for all of their cooperation and assistance. We are also grateful to Mr. and Mrs. Hubert Burns for allowing access to their land. We also want to thank Rich Pope for his assistance in plant identification.

REFERENCES
Bryant, A.A., J.R. Woster, 1978. Soil Survey of Warren County, Iowa USDA-SCS. U.S. Government Printing Office, Washington, D.C.
Carlson, R., 1962. Silent Spring. Houghton-Mifflin Co. Boston, Massachusetts.
Conrad, R. and S. Hess, 1998. Tallgrass Prairie national Preserve Legislative History, 1920-1996. National Park Service Midwest Support Office, Omaha, Nebraska.
Dewitt, T.A., 1978. Soil Survey of Story County, Iowa USDA-SCS. U.S. Government Printing Office, Washington, D.C.
Drohan, P.J., E.J. Ciolkosz and G.W. Petersen, 2003. Soil Survey Mapping Unit Accuracy in Forested Field Plots in Northern Pennsylvania. Soil Sci. Soc. Am. J.67:208-214.
Lin H.S., K.J. McInnes, L.P. Wilding, and C.T. Hallmark, 1999. Effects of Soil Morphology on Hydraulic Properties: I.Quantification of Soil Morphology. Soil Sci. Soc. Am. J. 63:948–954 (1999).
Nestrud L.M., J.R. Woster, 1979. Soil Survey of Jasper County, Iowa USDA-SCS. U.S. Government Printing Office, Washington, D.C.
Ogden, C.B., H.M. van Es, and R.R. Schindelbeck. 1997. A simple rainfall simulator for measurement of soil infiltration and runoff. Soil Sci. Soc. Am. J. 61:1041-1043.
Schroeder, W.L., S.E. Dickenson, and D.C. Warrington (ed.) 2004. Stress Analysis and Engineering Properties p. 59-82. In Soils in Construction., Prentice Hall, New Jersey
Thompson, J.R. 1992. Prairies, Forests and Wetlands. The Restoration of Natural Landscape Communities in Iowa. University of Iowa Press, Ames, Iowa.
van Es, H.M., C.B. Ogden, R.L. Hill, R.R. Schindelbeck, and T. Tsegaye. 1999. Integrated Assessment of Space, Time, and Management-Related Variability of Soil Hydraulic Properties. Soil Sci. Soc. Am. J. 63:1599-1608.