Franzmeier, D. P.

King, J. J.

English

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Morphology, Hydrology, and Management of Clermont SoilsJ. J. King and D. P. FranzmeierDepartment of AgronomyPurdue University, West Lafayette, Indiana 47907IntroductionThe Clermont soil occurs extensively on nearly level tabular divides of the II-linoian till plain in southeastern Indiana. Generally, it has been accepted that thesoil formed in 50 to 120 cm of loess over Illinoian glacial till. Recent investigations,however, have shown that the soil has a distinct paleosol surface, probablySangamon in age, about 2 to 3 m deep (Steinhardt and Franzmeier, 1979; Ruhe andOlson, 1980), which makes the origin of the material above the paleosol uncertain. Itis usually silt loam or silty clay loam in texture, but has a higher sand content thanclassical loess from the major loess sources such as the lower Wabash and WhiteRiver Valleys, and usually it has no distinct lithologic discontinuities. The 2 to 3 mdeposit is also thicker than loess is usually thought to be in southeastern Indiana.In spite of these relationships, however, it seems that eolian activity is a moreplausible explanation of the origin of the silty materials than any of the alter-natives.Within this surface silty deposit is a brittle subsurface horizon often called afragipan. Earlier, this layer was considered to be one of the strongest fragipans inthe soils of Indiana. Then, during a field study in Ohio and Indiana in 1971,pedologists decided that most of the Clermont pedons did not have horizons thatqualified as fragipans according to the then current definitions which were subse-quently published in Soil Taxonomy (Soil Survey Staff, 1975). This definition re-quires that a horizon must contain more than 60% brittle material which is inprisms that average more than 10 cm across. The pans observed had some brittlematerial but they were so riddled with krotovinas, probably crayfish burrows, thatgenerally they did not meet the 60% brittle requirement. Also, many of the prismsin the upper part of the pan were less than 10 cm across, which again did not meetthe requirements for a fragipan. This layer, however, is usually designated a Bxhorizon to indicate its brittle nature. As a result of this study the classification ofthe Clermont series was changed from Typic Fragiaqualf to Typic Ochraqualf in-dicating that there is no fragipan in the control section. It is in the fine-silty, mixed,mesic family. However, many pedons of the soil, as it occurs in the field, do havefragipans. Thus the natural soil landscape unit recognized as Clermont has aborderline fragipan but the classification of the taxonomic unit does not recognizeit.The Clermont soil (natural landscape unit) is a difficult one to manage. It is ex-cessively wet in the spring and planting is often late. In a dry summer crops sufferfrom drought because plant roots are not developed very deeply. Tile drainagegenerally has not been recommended because of the low permeability of the sub-soil, especially the fragipan (or fragipan-like horizon), and because it is difficult tofind suitable outlets for the tile in the broad divides. Instead, surface drainage hasbeen emphasized. This practice, however, increases surface runoff and results insignificant erosion during intense rainfall when the soil is bare or the crop is small.The objectives of this study were to study the hydrologic properties of theClermont soil, to identify which soil horizons are most limiting to water movement,and to relate these observations to soil management.416Soil and Atmospheric Sciences 417Materials and MethodsThe study was conducted in cooperation with the Agricultural EngineeringDepartment, Ohio State University. They were studying how drainage systemsfunctioned in soils that are difficult to drain (Schwab et al., 1979). The general ap-proach was to completely saturate a soil and then, by monitoring the drop in watertable levels and the rate of flow from a tile line, to calculate the drainable porosity(x) and the hydraulic conductivity-drainable porosity ratio (K/x) of the drainedlayers.The site selected was on the D. Wilson farm near Greensburg, Indiana (640 mE and 425 m S of NW corner, Sec. 32, T ION, R 10E, Decatur Co.), in which adrainage system with a 15 m (50 ft.) tile spacing had been installed in 1968 at adepth of about 1 m. During the spring of 1979 three rows of piezometers were in-stalled at right angles to the tile lines to monitor ground water levels. Then, duringperiods when natural rainfall was high, about five more cm of water was added byirrigation to insure a saturated soil. Two soil pits were dug in the saturated soil,one to intercept a tile line for outflow measurements and one halfway between tilelines to study and sample the soil.The soil was sampled by horizons and particle-size distribution, exchangeablecations, organic carbon, and pH were determined by standard procedures (Franz-meier et al., 1977). Bulk density was measured by the National Soil SurveyLaboratory at V3-bar tension (field capacity) and oven dryness using natural clodsamples (Soil Survey Staff, 1972). Hydraulic conductivity, Ksat, was measured, bythe Piezometer method. This procedure involved measuring the rate at whichwater entered a 10-cm deep hole augered below the bottom of a 5-cm diameter steelconduit called a piezometer (Luthin and Kirkham, 1949). The results plotted repre-sent averages of two to six replicate measurements.Results and DiscussionSoil Morphology and CharacterizationThe Clermont profile is dominated by silt loam texture and gray color to adepth of 235 cm. Below the plow layer, the A2 (24 to 38 cm) and Bl (38 to 64 cm)horizons have very weak platy and weak subangular blocky structure, respective-ly. The B21t (64 to 96 cm) has moderate subangular blocky structure with some clayfilms on ped surfaces. The Bxl horizon (96 to 145 cm) has brittle material within theprisms, but the prisms are relatively small, 5 to 10 cm across. The Bx2 horizon (145to 235 cm) has very coarse prisms (> 10 cm across), and conspicuous silt and clayfilms on the prism surfaces. It is a well developed fragipan according to currentdefinitions. Below the fragipan, at a depth at 235 cm, is the paleosol surface. Thechange in soil properties there is quite apparent when boring with an augerbecause of the 10% clay increase, the increase in firmness and the morphology ofthe paleosol. Details of the profile morphology are reported elsewhere (Indiana SoilSurvey Staff, 1980).In this Clermont profile the upper material, to 235 cm, has > 53% silt; below235 cm the material has < 43% silt (Figure 1). The sand content of the uppermaterial, 9-26%, is higher than in typical loess. The clay content of the Clermontsoil reaches an upper maximum of 26% (Figure 1) in the Bxl horizon and a secondmaximum of 36% in the paleosol (IIB22tb horizon). Sand content increasesdownward in the paleosol. Organic carbon content is low — 0.7% C in the Aphorizons and 0.3% C in the A2 and Bl horizons.418 Indiana Academy of Science% of Separate100350Figure 1. Particle-size distribution for Clermont silt loam.Hydraulic ConductivityWhen the pits were dug, after rain and irrigation, water was standing in smalldepressions in the field. The track-tractor with a back-hoe had difficulty crossingthe field in corn stubble because the soil surface was so wet and soft. Because ofthese very wet conditions we expected the soil pit to fill with water immediatelyafter digging, making it impossible to collect soil samples. We were surprised,however, to find that little water entered the soil pit. Most of what did enterseeped in at the lower boundary of the Ap horizon. Where a corn stalk protrudedinto the pit it acted as a conduit with water running from it in a steady drip. Occa-sionally, slabs of soil caved into the pit exposing large vertical planar surfaces ofthe subsoil and water could be seen moving along these surfaces. From these inter-Soil and Atmospheric Sciences 419,01a50100-E 150o8" 200-250Hydraulic Conductivity, cm/hrA2PlowpanBxlB2ltBX2 FraqiponUB22tb300-1Figure 2. Saturated hydraulic conductivity for Clermont silt loam.pretations it appeared to us that the layer limiting water movement was the A2horizon immediately below the plow layer and that once water got through thislayer it had a clear channel to the tile line through the well developed planar voidsof the B21t and Bxl horizons.Measurement of hydraulic conductivity on individual layers (Figure 2) con-firmed this observation. The slowest conductivities were in the paleosol (HB22tb)and the fragipan (Bx2) horizons, both of which are below the 1 m tile depth, and inthe A2 horizon, 24 to 38 cm deep.Table 1- Bulk density from saran-coated natural clods for Clermont silt loam(data from National Soil Survey Laboratory, SCO.Depth HorizonBulk densityl/3-bar oveng/cm1.57 1.631.58 1.881.54 1.591.49 1.771.77 1.8224-38 A238-64 Bl64-96 B21t96-145 Bxl145-235 Bx2420 Indiana Academy of ScienceThe low Ksat of the Bx2 horizon probably is related to its high bulk density(Table 1). The low Ksat of the A2 horizon, however, cannot be attributed to highbulk density; it might be related more to the arrangement, rather than the amount,of pore space.Tile Drainage StudyThe drawdown curve from the tile drainage study on Clermont is comparedwith curves from two other soils studied by the Ohio State group, Hoytville (MollicOchraqulf, fine, illitic, mesic), and Nappanee (Aerie Ochraqualf, fine, illitic, mesic).In Figure 3 the comparison shows that the shape of the curve for Clermont is dif-ferent from that for the other two soils, which is the more typical shape for slowlypermeable soils. The latter soils are high in clay in most of the profile and it is likelythat the horizons around the depth of the tile are the least permeable ones. In Cler-mont, on the other hand, the lowest Ksat values above the tile lines are in the A2horizon. Thus, the limiting layer is near the top of the drainage column in Clermontbut near the bottom of the column in the other soils. In the Hoytville and Nappaneesoils drainage begins quickly (Figure 3) and slows down as the water level islowered. In Clermont, however, drainage begins slowly and then accelerates.The conditions are analogous to draining water from a drinking straw. In onecase, as in Clermont, the straw is filled with water and one places a thumb over thetop of it to hold the water. The water stays in it until the thumb is released enoughto allow air to enter and then the straw drains quickly. If the straw were cripmedat the bottom to reduce its flow rate but not sealed completely, then filled withwater, and allowed to drain, it would begin to drain immediately and the rate wouldslow down with time as the head of water decreases. This is analogous to the Nap-panee and Hoytville soils.According to the tile spacing study (Schwab et al., 1979) the hydraulic conduc-tivity for a water table drop from to 20 cm is 2.2 cm/hr. This measurement isNappanee£lermont10 15 20 25 30Time j hoursFigure 3. Water table drawdown midway between tile lines for three soils(Schwab, et al. 1979. Their plot 2 of each soil.)Soil and Atmospheric Sciences 421within the range of Ksat values for the profile (Figure 2). Conductivity (k)measured by the tile drainage study is an equivalent K that is independent ofevaporation from the soil surface, but is influenced by the convergence of flow linesto the tile, by restriction of flow lines at the tile openings, and by deep seepagebelow the tile to lower horizons. The drainage study also represents a much largersoil area than does the piezometer method which is more specific for differencesamong horizons. For comparison, Ksat measurements by the piezometer methodranged from about 0.01 to 100 cm/hr for selected horizons of soils in Indiana, butthese horizons probably did not represent the full range of hydraulic conductivityrates.Soil ManagementThese results raise some interesting questions about management anddrainage of the Clermont soil. The rate-limiting horizon, instead of being quitedeep, is near the surface where it can be more readily managed. The question ishow best to manage it. Because surface drainage systems often result in erosion ofbare soil it appears that it would be desirable to remove some of the water throughthe profile in a tile line rather than across the soil surface. This requires that theconductivity of the A2 horizon-plowpan be increased which could be done bymechanical (tillage) or biological (plants, worms, etc.) methods. Because of the veryweakly developed structure of the A2 horizon we believe that tillage would havevery little lasting effect. Also, we question whether a layer that has deteriorated instructure under tillage can be improved by more tillage. On the other hand, ver-tical mulching, the practice of placing plant residues in vertical slits in the soil,might be investigated on these soils. Kohnke (1971) studied the practice on somewell-structured soils and found no pronounced runoff reduction or corn yield in-crease. It may be more beneficial, however, on poorly-structured soils such as Cler-mont.A more promising method may be biological, through winter cover crops orcrop rotations with a forage crop. A winter cover crop which has live roots duringthe fall, winter and early spring should have these advantages:1. The roots would penetrate the A2-plowpan horizon allowing water and airto pass through it more readily. In the analogy of the drinking straw thiswould allow air to enter through the top of the column to drain it.2. Plant growth during spring would help dry the soil when it is usually toowet for farming.3. Addition of organic matter, over several years, would increase the ag-gregation and structural development of the upper soil horizons. Thiswould result in better conductivity and root penetration.4. Plant cover would increase the infiltration of these soils, which form sur-face crusts readily, and result in less erosion because of the direct effect ofplant cover and the indirect effect of more infiltration and less runoff.A possible disadvantage of a winter cover crop is that it may reduce soiltemperatures and slow early growth of the next crop.We believe that tile drainage, tillage, and cropping practices should be studiedon the Clermont soil.SummaryMeasurements of saturated hydraulic conductivity by the piezometer methodand tile-drainage studies in the Clermont soil showed that the least permeable422 Indiana Academy of Sciencehorizons are the A2-plowpan, fragipan, and paleosol horizons. Since the last two arebelow the depth of tile lines, the A2-plowpan must be the one that limits watermovement to the tile. This horizon is shallow enough so that its conductivity can beimproved by growing plants and, possibly, tillage. We suggest that tile drainage ofClermont combined with a winter cover crop will reduce soil erosion and providebetter growing conditions for the subsequent crop.Literature Cited1. Franzmeier, D. P., G. C. Steinhardt, J. R. Crum, and L. D. Norton. 1977. Soilcharacterization in Indiana: I. Field and laboratory procedures. Purdue Univ.Ag. Exp. Sta. Res. Bull. 943. 30p.2. Indiana Soil Survey Staff. 1980. Soil characterization in Indiana: V. 1978 Data.Purdue Univ. Agr. Exp. Sta. Bull. 274. 194 p.3. Kohnke, H. 1971. Experiences with vertical mulching. Proc. Indiana Acad.Sci. 80:468-475.4. Luthin, J. N. and D. Kirkham. 1949. Piezometer method for measuringpermeability of soil in situ below a water table. Soil Sci. 68:349-358.5. Ruhe, R. V. and C. G. Olson. 1980. Soil welding. Soil Sci. 130:132-139.6. Schwab, G. 0., D. E. Kopcak, J. D. Gordos, and C. J. Olosky. 1979. Fieldevaluation of subsurface drainage (Phase II research report). Ag. Eng. Dept.,Ohio Ag. Res. and Dev. Center, Columbus. 21 p. (mimeo).7. Soil Survey Staff 1972. Soil survey laboratory methods and procedures for col-lecting soil samples. Soil Survey investigations Report No. 1. U.S. Dept. Ag.Soil Conservation Service. 63 p.8. Soil Survey Staff. 1975. Soil taxonomy. U.S. Govt. Printing Of. 754 p.9. Steinhardt, G. C. and D. P. Franzmeier. 1979. Chemical and mineralogicalproperties of the fragipans of the Cincinnati catena. Soil Sci. Soc. Am. J.43:1008-1013.

Morphology, Hydrology, and Management of Clermont Soils

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Morphology, Hydrology, and Management of Clermont Soils

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