University of Wisconsin - Madison | Department of Soil Science

1998 AGRONOMY ABSTRACTS

Division A-3 - Agroclimatology and Agronomic Modeling

Consistency of Micrometeorological Measurements of Surface Energy Fluxes. T.E. Twine*, W.P. Kustas, J.M. Norman, D.R. Cook, P.R. Houser, T.P. Meyers, J.H. Prueger, and P.J. Starkus, Univ. of Wisconsin-Madison.

Division A-5 - Enviromental Quality

Recent Advances in Understanding the Chemistry of Cr(VI), Pb(II) and Hg(II) in Soils: Adsorption to Mineral Surfaces and Complexation by Humic Substances. W.F. Bleam*, P.A. Helmke, and M.D. Szulczewski, Univ. of Wisconsin-Madison; P.R. Bloom, Univ. of Minnesota; R.W. Taylor, Alabama A&M Univ.; F.J. Weesner, Neptune Assoc.; K. Xia, Kansas State Univ.

Effect of Land Application of Biosolids, Dairy Manure, and Fertilizer on Nutrient Movement in Soils and Crops. A.E. Peterson*, R.P. Wolkowski, L.G. Bundy, T.H. Wright, and D.S. Taylor, Univ. of Wisconsin-Madison and Metropolitan Sewerage District.

Evaluating the Reductive Capacity of Humic Substances: Reactions between Thiol/Thio Groups and Chromate. M.D. Szulczewski*, K. Xia, P.A. Helmke, W.F. Bleam, and R.W. Taylor, Univ. of Wisconsin-Madison and Alabama A&M Univ.

Farm Management, Research and Extension Applications of the Arlington Station GIS. J.K. Bukovac, S.G. Mukhtyar, S.J. Ventura, R.F. Harris*, D.H. Mueller, and R.P. Wolkowski. Univ. of Wisconsin-Madison.

Interactive 3-D Visualization of Molecules and Minerals in Soil Science Instruction. P. Barak*, E.A. Nater, J.L. Boettinger, and A.H. Duin, Univ. of Wisconsin-Madison, Univ. of Minnesota, and Utah State Univ.

Division S-1 - Soil Physics

Profile Cone Penetrometer (PCP) Development for Soil Physical Property Characterization. D.J. Rooney* and B. Lowery, Univ. of Wisconsin-Madison.

Particle Size Analysis Using a Dielectric Method. G. Starr*, P. Barak, B. Lowery, and M. Avila-Segura, Univ. of Wisconsin-Madison and Ohio State Univ.

In-Situ Measurements of Nitrate Leaching with Equilibrium Tension Lysimeters. K.R. Brye*, J.M. Norman, L.G. Bundy, and S.T. Gower, Univ. of Wisconsin-Madison.

Development of a Soil Video Imaging System (SoilVIS) in Conjunction with a Profile Cone Penetrometer (PCP). S.H. Lieberman*, D.J. Rooney, and B. Lowery, SPARWAR Systems Center, San Diego, CA and Univ. of Wisconsin-Madison.

Division S-2 - Soil Chemistry

Two-Dimensional Nuclear Overhauser Effect Spectroscopy (NOESY) of Organic Compounds Sorbed by Humic Macromolecules. E.G. Kim*, Y.Y. Chien, and W.F. Bleam, Univ. of Wisconsin-Madison.

Polarized X-Ray Absorption and Magnetic Studies of Oriented Clay Films: Dy(III) Adsorption by Zirconia-Pillared Clay. S. Yoon* and W.F. Bleam, Univ. of Wisconsin-Madison.

Uptake of Phosphorus by White Lupin and Soybean from Diverse P Pools in Fertilized and Unfertilized Soil. C.A. Bissani*, A.E. Boaretto, P.A.V. Escosteguy, and P.A. Helmke, Univ. of Wisconsin-Madison.

Division S-3 - Soil Biology and Biochemistry

Temporal Dynamics of LF Mass and Composition, Microbial Indicators, and Pythium Root Rot of Cucumber in a Compost-Amended Sand. A.G. Stone*, S.J. Traina and H.A.J. Hoitink, Univ. of Wisconsin-Madison and Ohio State Univ.

Division S-4 - Soil Fertility and Plant Nutrition

Site-Specific Factors Affecting Corn Response to Starter Fertilizer. L.G. Bundy* and T.W. Andraski, Univ. of Wisconsin-Madison.

Theory of Ion Exchange Membrane Use in Soils and Sediments. L.R. Cooperband*, Univ. of Wisconsin-Madison, W.M. Jarrell, Oregon Grad. Inst., and M.M. Abrams, Portland Bureau of Environ. Serv.

Efficiency of Foliar and Soil Applications of Urea to Young Citrus Plants. A.E. Boaretto*, P. Schiavinatto, T. Muraoka, and C.A. Bissani, CENA/USP and UFRGS, Brazil

The Nitrogen Economy of Irrigated Potatoes. S.A. Wilner*, W.L. Bland, and C.J. Rosen, Univ. of Wisconsin-Madison and Univ. of Minnesota.

Influence of Soil Test and Topdressed K on Alfalfa Yield and Quality. P.E. Speth and K.A. Kelling,* Univ. of Wisconsin-Madison.

Division S-5 - Pedology

Soil Mapping Applications Using a Profile Cone Penetrometer (PCP). D.J. Rooney*, B. Lowery, K. McSweeney, and S. Grunwald, Univ. of Wisconsin-Madison.

Continuous Description of Soil Attributes on a Landscape in Southern Wisconsin. S. Grunwald*, K. McSweeney, B. Lowery, and D.J. Rooney, Univ. of Wisconsin-Madison.

Soil-Forming Processes and Modern Soil Taxonomic Systems. J.G. Bockheim* and A.N. Gennadiyev, Univ. of Wisconsin-Madison.

Multiple Scale Analysis of Sustainable Land Management: A Case Study from Central Honduras. P.J. Ericksen*, K. McSweeney and F.W. Madison, ICRAF-Nairobi and Univ. of Wisconsin-Madison.

Division S-6 - Soil and Water Management and Conservation

Atrazine and Nitrate Leaching Potential Within Depressional Areas. J.R. Samuelson* and B. Lowery, Univ. of Wisconsin-Madison.

Leaching of Nitrate and Atrazine for Three Erosion Phases of a Dubuque Silt Loam with Organic Amendments. F.J. Arriaga* and B. Lowery, Univ. of Wisconsin-Madison.

Division S-8 - Nutrient Management and Soil and Plant Analysis

Alfalfa Responses to Nitrogen as Affected by Soil pH. K.A. Kelling* and J.B. Peters, Univ. of Wisconsin-Madison.

Division A-3 - Agroclimatology and Agronomic Modeling

The Univ. of Wisconsin-Madison set up an eddy covariance system next to ten other flux-measuring systems in Oklahoma during the Southern Great Plains Experiment in 1997. This suite of systems comprised seven eddy covariance systems from several manufacturers and three Bowen ratio systems from two manufacturers. Comparisons between the Wisconsin eddy covariance system and other eddy covariance latent heat flux measurements showed rms differences of 49 Wm-2, while those between the Wisconsin eddy covariance system and Bowen ratio systems showed rms differences of 128 Wm-2. Unlike the Bowen ratio system, the eddy covariance system does not assume energy budget closure. Despite the difference in manufacturers, all systems had similar closure rates of near 80%. After forcing closure, rms differences for the comparison between Wisconsin and other eddy covariance latent heat fluxes dropped to 27 Wm-2, while those between the Wisconsin eddy covariance system and Bowen ratio systems dropped to 99 Wm-2. Methods of forced closure will be discussed as well as how this might affect the consistency of fluxes.
J.M. Norman, (608) 262-4576, norman@calshp.cals.wisc.edu

Division A-5 - Enviromental Quality

Recent Advances in Understanding the Chemistry of Cr(VI), Pb(II) and Hg(II) in Soils: Adsorption to Mineral Surfaces and Complexation byHumic Substances. W.F. Bleam*, P.A. Helmke, and M.D. Szulczewski, Univ. of Wisconsin-Madison; P.R. Bloom, Univ. of Minnesota; R.W. Taylor, Alabama A&M Univ.; F.J. Weesner, Neptune Assoc.; K. Xia, Kansas State Univ.

Chromium, lead, and mercury serve to illustrate recent advances in our understanding of trace metal chemistry and the range of chemical processes that come into play when trace metals interact with soil components. Redox processes coupled to both inorganic and organic reducing agents dominate chromium chemistry. Adsorption at mineral interfaces and complexation by humic substances influence lead chemistry. Mercury cations, both inorganic and organometallic, show a marked preference for humic thiol/ bisulfide ligands over oxygen ligands.
W.F. Bleam, (608) 262-9956, wfbleam@facstaff.wisc.edu

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Biosolids, dairy manure, and N fertilizer were applied on a Plano silt loam (prairie) soil (PoB) in spring 1994, 1995, and 1996. The different rates of N fertilizer were 0, 56, 112, 168, and 224 kg/ha. Biosolids and manure were applied at one rate about equal to the 168 kg/ha fertilizer treatment. Corn was grown as the indicator crop. Soil solution samples collected from porous-cup samplers at 1 m indicate the greatest increase in nitrate-N from the 156 and 224 kg/ha treatments. No treatment increased the Cu, Zn, Pb, or Ni found in the soil leachate. Ear leaf samples indicated all treatments deficient in N. Grain samples showed very little difference between treatments for all elements. Yields were very good on the treated plots, with only 56 kg/ha N being unsatisfactory. Top yields were 8.91 and 10.1 Mg/ha. Results of this 3- year study indicate no environmental problem from the proper application of biosolids, manure, or fertilizer. Such applications resulted in excellent crop growth, predictable N response and no movement of heavy metals to corn grain or to the subsoil.
A.E. Peterson, (608) 262-2631, aepeters@facstaff.wisc.edu

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The reduction of Cr(VI) to Cr(III) occurs in the presence of several forms of organic matter, including cow manure, citric and gallic acids, fulvic acids, and humic acids. The relevant reducing components have not, however, been identified, although carbonyls are the suspected electron donors. Various humic organosulfur compounds, such as thiols and sulfides, with potential reducing capacity exist in organic matter. X-ray absorption near-edge structure (XANES) spectroscopy reveals the oxidation-state speciation of sulfur in natural and allows one to monitor the flow of electrons in both sulfur and chromium spectra.
M.D. Szulczewski, (608) 262-0397, mszulcze@students.wisc.edu

Division A-7 - Agricultural Research Station Management

Farm Management Applications of the Arlington Agricultural Research Station GIS. D.H. Mueller*, S.G. Mukhtyar, J.K. Bukovac, S.J. Ventura, and R.F. Harris. Univ. of Wisconsin-Madison.

The Arlington Agricultural Research Station (ARS) geographic information system (GIS) involves an interactive ArcView data base that integrates photographic images with layers of information on fields and buildings, land use, crop yields, and soil, topographic, hydrologic and geologic characteristics. Avenue (the customizing and development environment for ArcView) provides a link to crop yield and management data maintained in an Access database by the Arlington ARS headquarters, and allows customization of the Arlington GIS for specific farm management applications. Custom applications include automating the production of daily work plans in the form of application maps, site selection for assigning experimental plots based on the researcher's requirements, delineation of subplots using GPS and other methods, and integrating multiple sources of data such as historical treatment records, yield data, and remotely sensed images with the GIS database. Examples of farm management applications are presented.
R.F. Harris, (608) 263-5691, rfharris@facstaff.wisc.edu

Division A-8 - Integrated Agricultural Systems

CLORAT-Concentrated Livestock Operation Rapid Assessment Tool. W.L. Bland, Univ. of Wisconsin-Madison.

Animal agriculture is consolidating into large operations, with environmental, economic, and social implications. These implications broaden the list of parties interested in the decision to create a concentrated livestock operation (CLO). Local elected officials and government agencies must consider competing values and interests when deciding to permit a proposed CLO, and public debate is often acrimonious. We are creating an information system (CLORAT) to bring to this debate current relevant knowledge. CLORAT is intended to serve and be accessible to all interested parties via the Internet. Components include databases and calculators for livestock feed requirements and manure production, and geographically distributed databases of land use, crop acreage, and livestock numbers. Contributions to the area economy are estimated through an input-output model. CLORAT is rapidly customized for each specific proposal by selecting the relevant data and calculators from a collection that covers likely types of operation and locations
W.L. Bland, (608) 262-0221, wlbland@facstaff.wisc.edu

Computer Software Scene

Critical Site GIS Coverages for Water Quality Protection. S. Grunwald*, R.F. Harris, K. McSweeney, S.J. Ventura, and B. Lowery. Univ. of Wisconsin-Madison.

A geographic information system (GIS) for the UW Arlington Agricultural Research Station in southern Wisconsin has been used to delineate critical sites that have a high potential for leaching of chemicals such as nitrate and pesticides into the groundwater, and to distinguish them from areas with a low risk for leaching. Coverages represent spatial distributions and integration of topographic attributes, hydrologic and soil characteristics, land use, and management. Simulation modeling facilitates identification of critical sites and derivation of scenarios for different land use and management practices. Field- and farm-scale monitoring of study areas located at different landscape positions integrating different landscape characteristics, is used to provide experimental data on critical sites and verify simulation modeling of hydrologic fluxes and leaching of nitrate and pesticides. GIS analyses are then used to extend results across a more extensive landscape.
S. Grunwald, (608) 265-3331, sgrunwald@facstaff.wisc.edu

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A geographic information system (GIS) for the Univ. of Wisconsin, Arlington Agricultural Research Station (ARS), a 2,037-acre facility with 17 cooperating departments, serves as a GIS model for the other 11 UW research stations. To date, the Arlington GIS has incorporated core feature-, grid-, and image-based data on fields and buildings, land use, crop yields, and soil, topographic, hydrologic and geologic characteristics. These data are integrated into diverse views addressing issues such as farm production, critical site basins (areas with high potential for groundwater contamination), and grid-sampled nutrient analyses. Spatial data linked with historical records are updated periodically, and made available to users. The Arlington GIS, as presented in this ArcView demonstration, provides a platform for linking spatial data and information from UW ARS researchers, extension agents, and farm managers to provide a basis for making more efficient, profitable, and environmentally sustainable management decisions.
R.F. Harris, (608) 263-5691, rfharris@facstaff.wisc.edu

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The function of soil components-both organic and inorganic-is largely determined by their 3-dimensional structure. Student understanding of 3-D spatial concepts has been largely hampered by the inherent nature and the quality of instructional aids currently used in the classroom, consisting mainly of 2-D illustrations and physical models. Recent advances in computer software and www browser plug-ins permit on-screen display of interactive computer models that are fully rotatable, with highlights, shadows, and perspective to create "2-½D" images that simulate 3-D. These interactive visualizations may be incorporated into HTML modules, combined also with text, questions, highlighting features, and other appropriate instructional materials. The "Minerals and Molecules Project" has formed to produce the Virtual Museum of Minerals and Molecules, which has made a number of modules available for classroom, computer laboratory, or home study from internet server at URLs: /virtual_museum/ or http://www.soils.agri.umn.edu/virtual_museum/ .
P.W. Barak, (608) 263-5450, pwbarak@facstaff.wisc.edu

Division S-1 - Soil Physics

Profile Cone Penetrometer (PCP) Development for Soil Physical Property Characterization. D.J. Rooney* and B. Lowery, Univ. of Wisconsin-Madison.

A profile cone penetrometer (PCP) was developed and tested for use as a tool to rapidly and precisely delineate changes in soil physical and morphological properties to a depth of 1.3 m. The PCP is a hybrid penetrometer that combines attributes from both the American Society of Agricultural Engineers and the American Society for Testing and Materials specifications. The PCP measures penetration resistance using a hydraulically driven cone tip with a 60-degree angle and a diameter of 2 cm connected to a 1.6-cm diameter rod. A load cell was used to measure force of penetration and a string potentiometer to measure depth. The PCP was field tested on a 200-m square sloping landscape using a 10- m grid. At lower landscape positions, the PCP shows subtle changes in penetration resistance as values generally remained below 1000 Pa to a depth of 130 cm. Data collected from test locations on the upper slope indicate increased variability throughout the soil profile and penetration resistance values increasing to 3000 Pa at a depth range of 100 to 130 cm. Morphological properties observed from soil cores confirmed the changes in soil profile recorded by the PCP.
D.J. Rooney, (608) 262-0415, djrooney@students.wisc.edu

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Particle Size Analysis Using a Dielectric Method. G. Starr*, P. Barak, B. Lowery, and M. Avila-Segura, Univ. of Wisconsin-Madison and Ohio State Univ.

Limitations of traditional methods for particle size analysis warrant the investigation of new techniques. A method based on the difference between the dielectric constant of soil solids about (~4) and the dispersing solution (~80) has been developed and investigated as an alternative to these including the pipette method. We determined changes in particle concentration with a coaxial probe located near the surface of a dispersed soil suspension by monitoring changes in dielectric constant using a network analyzer. A single point calibration was obtained using the known initial concentration and a dielectric constant of 4 for silt to determine the amount of silt settled with time. Com- parisons between the silt/clay fractions obtained using the pipette method and the dielectric method showed agreement to better than + 2%. Using the dielectric method, particle size distributions could be measured on a 2-g sample with 400-s settling time because the effective depth of measurement was only 1.3 mm. The combination of speed, automation, small sample size, and nearly continuous data should be balanced against the higher cost of the dielectric method.
G. Starr, (614) 688-3354, starr.69@osu.edu

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In-Situ Measurements of Nitrate Leaching with Equilibrium Tension Lysimeters. K.R. Brye*, J.M. Norman, L.G. Bundy, and S.T. Gower, Univ. of Wisconsin-Madison.

Field measurements of drainage and solute leaching are indispensable in the context of understanding the dynamics of the hydrologic and nutrient cycles of any ecosystem. An equilibrium tension lysimeter (ETL) was designed and replicates were installed in a natural prairie, and N-fertilized no-tillage and chisel plow agroecosystems to measure drainage through undisturbed Plano silt loam soil. The ETLs monitor drainage continuously at 1.4 m below the soil surface through a 0.2-µm pore diameter stainless steel porous plate (0.19 m2). Heat dissipation sensors were used as tensiometers to record variations in matric potential inside and outside the ETLs sampling area. Tension was maintained on lysimeters according to the matric potential experienced by the surrounding bulk soil. Lysimeter drainage variability between replicates was smallest for the prairie (CV=5.9%) and largest for the N-fertilized chisel plow agroecosystem (CV=29.2%). Nitrate losses were smallest for the prairie (<0.3 kg ha-1). Based on 825 days of continuous measurements, nitrate losses were 155 kg ha-1 (CV=4.1%) for the fertilized chisel plow agroecosystem and 165 kg ha-1 (CV=22.0%) for the fertilized no-tillage agroecosystem.
K.R. Brye, (608) 262-0415, krbrye@students.wisc.edu

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A soil video imaging system has been designed for use in the soil environment. Rapid visualization of various soil attributes such as texture or color can have a dramatic impact on the efficiency and accuracy of soil sampling techniques. A truck-mounted, hydraulically driven cone penetrometer is used to push the system through the soil profile to view the soil strata. Soil in contact with the side of the probe is imaged through a sapphire window and lens with a miniature CCD color camera. The soil is illuminated with an array of white light emitting diode located in the probe. The video signal from the camera is returned to the surface real-time where it is displayed on a video monitor, recorded on a video cassette recorder, and/or captured digitally with a frame grabber installed in a microcomputer system. The system images an area that is 2 x 2.5 mm, which provides a magnification factor of approximately 100 times when viewed on a standard computer monitor.
D.J. Rooney, (608) 262-0415, djrooney@students.wisc.edu

Division S-2 - Soil Chemistry

Two-Dimensional Nuclear Overhauser Effect Spectroscopy (NOESY) of Organic Compounds Sorbed by Humic Macromolecules. E.G. Kim*, Y.Y. Chien, and W.F. Bleam, Univ. of Wisconsin-Madison.

The domain harboring neutral organic contaminants in humic macromolecular aggregates influences, among other things, the conformation of small organic molecules. Two-dimensional homonuclear proton NOESY nuclear magnetic resonance studies of humic micellar solutions containing 2-octanone reveal intramolecular cross-peaks, appearing as "ridges," between octanone and humic macromolecules and intermolecular cross- peaks, appearing as isolated "peaks," between the various octanone protons. The octanone intermolecular cross-peaks clearly show the compact conformation of octanone molecules in the sorbed state.
E.G. Kim, (608) 262-0397, egkim@students.wisc.edu

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Polarized X-Ray Absorption and Magnetic Studies of Oriented Clay Films: Dy(III) Adsorption by Zirconia-Pillared Clay. S. Yoon* and W.F. Bleam, Univ. of Wisconsin-Madison.

The mobility of actinide elements through soils, sediments, and aquifers poses significant environmental risks. Zirconium oxide is a recent candidate for immobilization of high-level nuclear wastes, since its compounds can immobilize actinides in its crystal structure. Zirconia-pillared clay can be a more effective candidate for in-situ immobilization, with its high surface area and high thermal stability. We adsorbed Dy(III) on zirconia-pillared clay, as an analog of Pu(III), relying upon the similarities between lanthanide and actinide chemistry. This study determines whether Dy(III) adsorbed by zirconia-pillared smectite binds to the zirconia pillars and, if so, whether the adsorbed ions form clusters nucleated on the zirconia pillars. We examined the chemical environment of Dy(III) adsorbed on pillared clay using polarized x-ray absorption fine structure (P-XAFS) on oriented clay film and magnetic susceptibility.
W.F. Bleam, (608) 262-9956, wfbleam@facstaff.wisc.edu

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Uptake of Phosphorus by White Lupin and Soybean from Diverse P Pools in Fertilized and Unfertilized Soil. C.A. Bissani*, A.E. Boaretto, P.A.V. Escosteguy, and P.A. Helmke, Univ. of Wisconsin-Madison.

White lupin shows adequate P nutrition in soils with low available P. Citric acid exudation by lupin root clusters (proteoid roots) is thought to be the main mechanism that mobilizes insoluble soil P as a response to low P. The effects of soil P levels (10, 15, and 20 mg kg -1 ) and growth stage (20, 35, and 50 days after seeding) on P uptake by lupin (Lupinus albus L., Ultra) and soybean (Glycine max L. Merr., Corsoy 79) were studied. Plants were grown under controlled conditions in pots containing 900 g of Plano silt loam soil (Typic Argiudoll) at pH 5.8. The number of proteoid root clusters increased with time and decreased with increasing P, but they were present at all P levels. The citrate concentration in the rhizosphere soil increased with time but it was not affected by P level. While lupin showed no response in dry matter, soybean shoots increased and roots decreased with increasing P levels. Higher soil P levels result in higher P uptake by soybean but not for lupin. Independent of soil P level, lupin had lower values of 32 P specific activity than did soybean. The values of isotopically exchangeable P decreased with time in both species and were significantly higher for lupin than soybean. The results show that lupin acquires P from diverse P pools independent of growth stage and available P level.
P.A. Helmke, (608) 263-4947, pahelmke@facstaff.wisc.edu

Division S-3 - Soil Biology and Biochemistry

The mass and chemical composition (by DR-FTIR and 13C CPMAS NMR) of compost light fraction (LF), microbial biomass and community composition, and suppressiveness to Pythium root rot were investigated as compost decom-posed in sand over a 506-day period. Suppression was sustained through day 375. During this period (1) microbial biomass declined, but there was no change in FDA activity; (2) there was a decline in LF mass, but little change in LF chemistry; and (3) gram negative PLFAs increased and gram positive and actinomycete PLFAs declined. Between days 375 and 426, suppression was lost, FDA activity declined, and significant reductions in aromatic and aliphatics (as determined by DR-FTIR), or O-alkyl and alkyl-C (as determined by 13C CPMAS NMR) contents were observed. Fungal PLFAs increased and gram positive and actinomycete PLFAs declined. Less-decomposed coarse and mid-sized fractions dominated the suppressive LF, while a more-decomposed fine fraction dominated after the loss of suppression. The composition of the suppressive compost-derived LF (by NMR) was similar to forest organic horizon and soil unprotected light fraction NMR literature values.
A.G. Stone, (608) 262-0383, agstone@facstaff.wisc.edu

Division S-4 - Soil Fertility and Plant Nutrition

Site- Specific Factors Affecting Corn Response to Starter Fertilizer. L.G. Bundy* and T.W. Andraski, Univ. of Wisconsin-Madison.

The need for starter fertilizer (SF) in corn production is questioned for economic and environmental reasons because many soils have phosphorus (P) test levels above those needed to maximize yields. We evaluated corn yield response to SF at 100 on-farm sites, most having excessively high (EH) soil test P and K levels, over a 3-yr period. Treatments (three replications) of none or an average rate of 15+11+27 (N+P+K) kg/ha were placed 5 cm below and 5 cm laterally from the seed at planting. Statewide, SF increased yields by about 0.25 Mg/ha each year. For individual sites, yield response to SF ranged from -0.6 to +2.6 Mg/ha, and 40% of the sites had a positive economic response to SF. The percentage of responsive sites was linearly related (r2=0.51) to the sum of hybrid relative maturity (RM) and the day of the year of planting (PDRM). Responses are most likely at later planting dates using longer RM hybrids (PDRM >235) and where soil test K levels are below 140 mg/kg. The SF response with late planting dates and hybrids may be due to stimulation of early season growth rates by SF.
L.G. Bundy, (608)263-2889, lgbundy@facstaff.wisc.edu

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Theory of Ion Exchange Membrane Use in Soils and Sediments. L.R. Cooperband*, Univ. of Wisconsin-Madison, W.M. Jarrell, Oregon Grad. Inst., and M.M. Abrams, Portland Bureau of Environ. Serv.

Recent research has identified benefits of using ion exchange resin membranes placed directly in soils and sediments to assess ion mobility in situ . The combination of a fixed planar geometry, direct contact with soil, and known exchanger properties allows the user to characterize fundamental properties of the soil or sediment system, based on rates of ion accumulation on the membrane surface. This paper will discuss both the diffusion/ mobility aspects of ion transport, and the exchanger properties of the membranes, which determine how rapidly ions accumulate on the surface, and its ultimate capacity. Some studies have shown membrane-extracted ion concentrations to be well correlated with soil or sediment solution ion concentrations and plant nutrient uptake. Other studies suggest that soil mineralogy and texture influence membrane ability to sorb ions from the soil solution. Effects of temperature, soil water content, interfacial properties, etc. will be included in the discussion.
L.R. Cooperband, (608) 265-4654, lrcooperband@facstaff.wisc.edu

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Efficiency of Foliar and Soil Applications of Urea to Young Citrus Plants. A.E. Boaretto*, P. Schiavinatto, T. Muraoka, and C.A. Bissani, CENA/USP and UFRGS, Brazil

Foliar application of urea, an alternative method of N fertilization, has been accepted as a more efficient way for feeding plants than the conventional soil N application. Comparative studies between these methods of applying N to citrus plants are scarce. The objective of this study is to discuss this issue based on results of an experiment testing two methods of urea application to orange plants (Citrus sinensis L. Osbeck on Citrus limon L. Burm rootstocks). Young "Pera" orange plants were transplanted to pails containing 25 kg of soil and urea was applied on the soil from 45 to 180 days after transplanting (dap) or on the leaves from 45 to 360 dap. Solid urea or 15N-urea (2.5 to 7.5 g plant -1 ) was broadcast on the soil surface. A solution of urea or 15N-urea (22.4 g L -1 ) was spayed on the leaves by a manual device at volumes of 15 to 35 mL plant -1 . Plants were harvested and analyzed at 75, 120, 180, and 360 dap. The orange plants recovered proportionally more N from soil-applied urea. The recovery ranged from 33 to 61% and from 1 to 33% of the N amount applied on the soil and on the leaves, respectively. Higher N concentration and content and, consequently, dry matter production resulted from soil application. It was concluded that soil application of urea was more efficient than foliar application in supplying N to young orange plants.
C.A. Bissani, (608) 262-0397, cbissani@students.wisc.edu

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The Nitrogen Economy of Irrigated Potatoes. S.A. Wilner*, W.L. Bland, and C.J. Rosen, Univ. of Wisconsin-Madison and Univ. of Minnesota.

Leaching of N fertilizer from sandy soils may reduce potato yields when it prohibits the crop from acquiring sufficient quantities of N. Managers frequently face the question as to how much N may have been lost due to a particular precipitation event and whether this loss will result in reduced yields. We created a simple empirical model for farmers to monitor the interactions between N inputs, soil properties, and rainfall/irrigation events on soil nitrate concentrations and plant N availability. Our model uses a function to describe nitrogen accumulation in high yielding potato crops and the ability of the soil to meet this demand. The soil N pool is modeled considering: 1) precipitation, 2) irrigation, 3) estimated evapotranspiration, 4) pre-season soil nitrate concentrations, 5) the type and timing of nitrogen fertilizer inputs, 6) nitrogen transformations and behaviors in the soil, 7) soil bulk density and water holding capacity, and 8) total nitrogen and dry matter accumulation in the crop.
S.A. Wilner, (608) 265-9354, sawilner@facstaff.wisc.edu

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Influence of Soil Test and Topdressed K on Alfalfa Yield and Quality. P.E. Speth and K.A. Kelling*, Univ. of Wisconsin-Madison.

Although a significant number of experiments have demonstrated the responsiveness of alfalfa to topdressed K or have identified the soil test K level above which no K response is seen, relatively few have examined alfalfa response to the interactive effects of soil test and topdressed K. This experiment evaluated the influence of six rates of topdressed K (0 to 392 kg K 2 O ha -1 ) superimposed on existing soil test K levels ranging from 60 to 160 mg kg -1 on alfalfa yield and quality over a 4-yr period. Data from this experiment show that soil test K, topdressed K 2 O, or a combination can be used to optimize alfalfa yield and quality. At soil test levels of 90 to 120 mg K kg -1 , about 220 kg K 2 O ha -1 yr -1 were needed to optimize yields, and where soil test K exceeded 150 mg kg-1, little benefit was seen to topdressing. About 230 kg K 2 O ha -1 yr -1 appeared to maintain soil test K levels even though removals were, at times, higher. Forage K levels consistently exceeded 40 g kg -1 where topdress rates were more than 250 kg K 2 O ha -1 on soils testing more than 120 mg K kg -1 . Forage crude protein tended to decrease, whereas ADF and NDF generally increased with higher levels of available K.
K.A. Kelling, (608) 263-2795, kkelling@facstaff.wisc.edu

Division S-5 - Pedology

Soil Mapping Applications Using a Profile Cone Penetrometer (PCP). D.J. Rooney*, B. Lowery, K. McSweeney, and S. Grunwald, Univ. of Wisconsin-Madison.

Current ground truthing methods used to verify soil mapping units at less than a 10-m scale in the field are inefficient and costly. Intensive land use practices such as precision agriculture frequently require more detailed information regarding soil physical properties than typically exists in most available soil surveys. A profile cone penetrometer (PCP), when used in conjunction with a global positioning system, can provide spatially precise, quantitative information on changes in soil texture, water content, and bulk density in a three-dimensional format as an input to geographic information systems. Data collected with the PCP show clear changes in soil properties with depth and were confirmed using profile descriptions from 2.54-cm diameter soil cores. Combining three-dimensional PCP data with existing soil attribute information will provide a rapid and effective means to update soil surveys and improve the efficiency and cost effectiveness of sampling techniques.
D.J. Rooney, (608) 262-0415, djrooney@students.wisc.edu

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Continuous Description of Soil Attributes on a Landscape in Southern Wisconsin. S. Grunwald*, K. McSweeney, B. Lowery, and D.J. Rooney, Univ. of Wisconsin-Madison.

To address water quality issues such as nitrate and pesticide leaching, a prerequisite is understanding the distribution of soil attributes across the landscape. This study was undertaken to characterize the spatial variation of several soil attributes on a field in southern Wisconsin. Soil data were collected on a 10x10-m grid using profile cone penetrometer (PCP) technology. Using PCP, continuous vertical soil data were collected, and attributes between grid points were interpolated using geostatistics. Geographic information system technology was effectively used to superimpose topographic attribute data. Heterogeneous and homogeneous areas of soil attribute and topographic attribute data were delineated and their relationships analyzed.
S. Grunwald, (608) 265-3331, sgrunwald@facstaff.wisc.edu

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Soil-Forming Processes and Modern Soil Taxonomic Systems. J.G. Bockheim* and A.N. Gennadiyev, Univ. of Wisconsin-Madison.

Modern soil taxonomic systems, including Soil Taxonomy (ST), the recent World Reference Base (WRB) for Soil Resources, and some Russian systems used over the past 35 yr classify soils on the basis of diagnostic horizons, properties, and materials. While this practice is appropriate for classifying individual soils, it has stifled research in soil-forming processes. A knowledge of soil processes is important for understanding earth's dynamic systems, developing quantitative models of pedogenic systems, and illustrating the genetic underpinnings of modern soil classification schemes. Sixteen key soil-forming processes are identified and linked to diagnostic horizons, properties, and materials in ST and WRB. These processes are illustrated in simple diagrams and include: argilluviation, biological enrichment of base cations, andisolization, paludization, gleization, humification, ferrallitization, podzolization, base cation leaching, vertization, cryoturbation, salinization, calcification, solonization, solodization, and silicification.
J.G. Bockheim, (608) 263-5903, bockheim@facstaff.wisc.edu

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Multiple Scale Analysis of Sustainable Land Management: A Case Study from Central Honduras. P.J. Ericksen*, K. McSweeney and F.W. Madison, ICRAF-Nairobi and Univ. of Wisconsin-Madison.

The objective of this study was to design a methodology of land evaluation suited to a hillside agroecosystem managed by subsistence farmers. A small catchment in Central Honduras was used as the study site. A multiple-scale, multiple-attribute approach was used, which incorporated farmers' percep- tions and concerns regarding soil quality and land management. At the fine scale (within fields), land use was found to have a greater influence than land form on soil quality. Using weighted and additive combinations of soil quality, irrigated agriculture was judged to be the least sustainable land use and coffee groves and forest patches the most sustainable. At broader scales (among land management units), type and extent of vegetation cover, nature of erosion, and type of boundary surrounding a given site, most strongly influenced transfer of water, nutrients and sediment. At the catchment scale, a coherent pattern relating land use to landform was not found, suggesting that land management was in a state of flux.
K. McSweeney, (608) 262-0331, kmcsween@facstaff.wisc.edu

Division S-6 - Soil and Water Management and Conservation

Atrazine and Nitrate Leaching Potential Within Depressional Areas. J.R. Samuelson* and B. Lowery, Univ. of Wisconsin-Madison.

Landscape conditions that do not have surface drainage outlets exist throughout the Midwest, especially in glaciated landscapes. We have defined these as depressional areas (DA). Landscape areas where surface drainage outlets exist have been defined as elevated areas (EA). Runoff water accumulates in the DA; therefore, we hypothesized that DA have the potential to contribute more groundwater pollution than EA, in part because of a higher soil water flux, leading to a higher solute flux. A field experiment to quantify leaching of agricultural chemicals within DA was initiated in spring 1997 at the Arlington Research Station, located in south central Wisconsin. Three sites, each with a DA and an EA, were identified for this study. DA ranged from 0.1 to 0.5 ha. Porous-cup samplers and porous-plate pan lysimeters were installed to measure bromide, nitrate, and atrazine plus metabolite concentrations at 1-m depth. Porous-plate pan lysimeters and water content reflectometry probes were used to measure soil water fluxes. Results from the 1997 field season show that bromide and nitrate fluxes are higher in the DA than the EA at two of the three sites. Bromide and nitrate concentrations are usually higher in the EA, but soil water fluxes are greater in the DA.
J.R. Samuelson, (608) 262-0415, jrsamuel@students.wisc.edu

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Leaching of Nitrate and Atrazine for Three Erosion Phases of a Dubuque Silt Loam with Organic Amendments. F.J. Arriaga* and B. Lowery, Univ. of Wisconsin-Madison.

Groundwater is an important source of drinking water in the U.S., supplying up to 50% of the total drinking water. In rural areas, it provides up to 90%. Agrichemicals can leach and potentially contaminate groundwater. In 1985, a study was established to investigate the effects of erosion on soil physical properties and corn production. Plots are located in the driftless region of southwestern Wisconsin. Three levels of erosion-slight, moderate and severe-were identified based on depth to residuum (2Bt horizon). In 1988, annual cattle manure applications were included to evaluate its potential for improving soil physical properties. Because of possible leaching of nitrate from manure, applications and macropore flow in manure plots, in 1997, porous-cup samplers, TDR probes and tensiometers were installed to investigate leaching of NO3, atrazine and metabolites. The wetting front on manure subplots seemed to move faster than in no-manure subplots. Higher NO 3 -N concentrations were observed on severely eroded manured than in non-manured subplots. However, no trend was noted in other treatments.
F.J. Arriaga, (608) 262-0415, farriaga@students.wisc.edu

Division S-8 - Nutrient Management and Soil and Plant Analysis

Alfalfa Responses to Nitrogen as Affected by Soil pH. K.A. Kelling* and J.B. Peters, Univ. of Wisconsin-Madison.

Several experiments have shown that few benefits are associated with the application of nitrogen fertilizer to well-nodulated alfalfa; however, alfalfa is sometimes grown at sub-optimal soil pH levels and one of the major benefits of liming is its influence on N 2 fixation. This experiment evaluated if the application of N fertilizer could overcome a soil pH limitation and the amount of N fertilizer needed. Alfalfa was seeded into plots with previously established pH levels from 4.8 to 6.7 at three Wisconsin locations. Following the initial harvest, N treatments of 0 to 168 kg N ha -1 in single or split applications were superimposed on the lime plots. At low pH levels (4.7 to 5.2), the addition of N about doubled harvested forage yields; however, in most cases, the low pH + N yields were not as high as those attained at the higher pH levels, and forage quality was 10 to 25% lower due to alfalfa stand loss. At pH levels of 6.5 to 6.8, the addition of N did not increase yields except following a severe winterkill. Responses were similar for equivalent rates for single or split-N applications.
K.A. Kelling, (608) 263-2795, kkelling@facstaff.wisc.edu