1996 AGRONOMY ABSTRACTS

Div. A-3 - Agroclimatology and Agronomic Modeling

Estimating Evapotranspiration and Photosynthesis on Regional Scale. J.M. NORMAN*, M.C. ANDERSON, G.R. DIAK, W.P. KUSTAS, and J.R. MECIKALSKI, Univ. of Wisconsin-Madison.

A Friendly Graphical Interface Between Complex Models and Large Input/Output Databases. M.C. ANDERSON*, J.M. NORMAN, M. LIVNY, and Y.E. IOANNIDIS, Univ. of Wisconsin-Madison.

Div. A-5 - Environmental Quality

Non-Equilibrium Field-Scale Pesticide Transport: Soil Cores vs. Solution Samplers. T.J. GISH. K.J.S. KUNG, C.S. HELLING, D. GIMENEZ, and A. SHIRMOHAMMADI. USDA-ARS, Beltsville, MD and Univ. of Maryland, College Park, MD.

Div. A-6 - International Agronomy

An Assessment of Soil Quality in a Hillside Agroecosystem of Honduras. P. ERICKSEN* and K. MCSWEENEY, Univ. of Wisconsin-Madison.

Div. A-8 - Integrated Agricultural Systems

Soil Quality: Building a Flexible Framework Based on Farmer Input. K. MCSWEENEY*, R.F. HARRIS, P. ERICKSEN, and D. ROMIG, Univ. of Wisconsin-Madison.

Computer Software Application Committee

A Soil Fertility Course Website A Prototype, One Year Later. P. BARAK, Univ. of Wisconsin-Madison.

Div. C-6 - Crop Quality and Utilization

Weather and Alfalfa Quality in Wisconsin. W.L. BLAND*, V.R. KANNEGANTI, and D.J. UNDERSANDER, Univ. of Wisconsin-Madison.

Div. S-1 - Soil Physics

Impact of Funnel-Type Preferential Flow on Sampling. K.J.S. KUNG*, S.H. JU, and C. HELLING, Univ. of Wisconsin-Madison and USDA-ARS.

Frequency-Domain Reflectometry for Water Content Measurement Using a Network Analyzer at Radio Frequencies. G.C. STARR* and B. LOWERY, Univ. of Wisconsin-Madison.

Measuring Instantaneous Solute Flux and Loading with Time Domain Reflectometry. G.L. HART* and B. LOWERY, Univ. of Wisconsin-Madison.

Div. S-2 - Soil Chemistry

Binding of Mercury (II) in Soil Organic Matter. U. SKYLLBERG* 1 , P. R. BLOOM 1 , E. A. NATER 1 , K. XIA 2 and W. BLEAM 2 , 1 Univ. of Minnesota and 2 Univ. of Wisconsin-Madison.

Complexation Constants of Cadmium, Copper, and Zinc with Soil Organic Matter. K. XIA*, P.A. HELMKE, and W.F. BLEAM, Univ. of Wisconsin-Madison.

Ion Transport Measurements in Soils by Use of Custom-Built Ion-Selective Microelectrodes and Computer-Driven Micromanipulator and Data-Logger. L.A. SHERMAN* and P. BARAK, Univ. of Wisconsin-Madison.

Role of Metals and Complexing Agents on Mineralization of Soil Organic Phosphorus by Root-Released Enzymes. X. HE and P. A. HELMKE*, Univ. of Wisconsin-Madison.

Effects of Organic Residues and Calcium and Magnesium from Dolomite on Soil Acidity and Activity of Trace Metals. J.A.G. SANTOS*, S. BUZETTI, and P.A. HELMKE, Univ. of Wisconsin-Madison.

Indigenous Free Ion Activity of Zinc as a Function of pH in Water Saturation Extracts of Soils from Brazil, North America, and Australia. P.A. HELMKE*, J.A.G. SANTOS, S. BUZETTI, K. XIA, and R. NAIDU, Univ. of Wisconsin-Madison.

Div. S-3 - Soil Biology and Biochemistry

Diagram-Assisted Redox Model for Mass Balancing Bioremediation by Microorganisms. R F. HARRIS* and W. J. HICKEY, Univ. of Wisconsin-Madison.

Div. S-4 - Soil Fertility and Plant Nutrition

Effect of Calcium and Magnesium Concentrations on the Uptake of Copper, Iron, Manganese and Zinc by Lettuce, Lupin, Soybean, and Wheat. S. BUZETTI*, J.A.G. SANTOS, and P.A. HELMKE, Univ. of Wisconsin-Madison.

Influence of Nitrogen Timing and Irrigation Methods for Potatoes. S.A. WILNER*, K.A. KELLING, and L.R. MASSIE, Univ. of Wisconsin-Madison.

Crop Residue Effects on Nitrogen Availability in No-till Corn. L.G BUNDY* and T.W. ANDRASKI, Univ. of Wisconsin-Madison.

Div. S-5 - Pedology

The NSSC Database for Permafrost-Affected Soils (Gelisols). J.G. BOCKHEIM1 , J.M. KIMBLE* 2 , C.L. PING 3 , and J.P. MOORE 3 , 1 Univ. of Wisconsin-Madison, 2 NRCS, and 3 Univ. of Alaska.

Soil Studies in the Lower Kolyma River Area, Far Eastern Russia. J. M. KIMBLE* 1 , C. TARNOCAI 2 , J. BOCKHEIM3 , C.L. PING 4 , AND S. SMITH 2 . 1 USDANRCS-NSSC, 2 Agri. and Agri-Food Canada, Ottawa, 3 Univ. of Wisconsin-Madison, 4 Univ. of Alaska, Fairbanks.

Development of a Three-Dimensional Soil-Landscape Model for the Loess Mantled Region of Southwestern Wisconsin. P.K. FALK*, K. MCSWEENEY, and S.J. VENTURA, Univ. of Wisconsin-Madison.

Micromorphological Alterations of Soils Under Long-Term Contrasting Prairie Management Systems. K.L. MALTONI*, UNESP/Ilha Solteira, Brazil, K. MCSWEENEY, Univ. of Wisconsin-Madison, and G. LeMASTERS, Dep. of Agric. Resource Management.

Div. S-6 - Soil and Water Management and Conservation

Carbon and Nitrogen Cycling on an Ecosystem Gradient from Cultivated Corn to Natural Prairie. KR. BRYE*, J.M. NORMAN, L.G. BUNDY, and S.T. GOWER, Univ. of Wisconsin-Madison.

Div. S-8 - Nutrient Management and Soil and Plant Analysis

Selenium and Trace Metals in Forage Samples. L.S. ZHANG* and S. M. COMBS, Univ. of Wisconsin-Madison/Extension.

Determination of Dissolved Organic Carbon by Inductively Coupled Plasma Mass Spectrometry. S.M. COMBS, L.S. ZHANG*, and Y.J. LIU, Univ of Wisconsin-Madison/Extension.

Designing Soil Test Recommendations to Meet Multiple Goals-Production, Economic, Environmental. K.A. KELLING* and S.M. COMBS, Univ. of Wisconsin-Madison.

Div. A-3 - Agroclimatology and Agronomic Modeling

Estimating Evapotranspiration and Photosynthesis on Regional Scales. J.M. NORMAN*, M.C. ANDERSON, G.R. DIAK, W.P. KUSTAS, and J.R. MECIKALSKI, Univ. of Wisconsin-Madison.

Regional-scale estimates of evapotranspiration and photosynthesis can be obtained from a Two-Source Time-Integrated Model using satellite observations of vegetation index, albedo, and radiometric temperature along with ancillary observations of wind speed, vegetation type, vapor pressure, and the atmospheric lapse rate near sunrise. The need for air temperature measurements is avoided by using the difference between radiometric temperatures at two times (about 1 and 5 hours after sunrise). Wind speed, vapor pressure, and lapse rate are interpolated from synoptic weather observations and vegetation type obtained from published maps. The dependence of radiometric temperature measurements on view angle is taken into account and tests using data from FIFE and Monsoon '90 indicate differences between measurements and model predictions of energy, water, and CO 2 fluxes comparable to measurement errors typical of standard micrometeorological methods for flux estimation (20 to 30%).

A Friendly Graphical Interface Between Complex Models and Large Input/Output Databases. M.C. ANDERSON*, J.M. NORMAN, M. LIVNY, and Y.E. IOANNIDIS, Univ. of Wisconsin-Madison.

With advances in computing technology and in our understanding of biophysical processes, the ability of biophysical models to generate new information is rapidly exceeding our capacity for ingesting it. The Cupid model, for example, a comprehensive description of soil-plant-atmospheric interactions, requires specification of approximately 200 input parameters and generates time series predictions of over 300 output variables. A detailed sensitivity study conducted with Cupid can become an overwhelming logistical challenge in terms of file management and data extraction. In this paper, we introduce the Zoo Desktop Experiment Management Environment, a system developed at the Univ. of Wisconsin for managing modeling experiments involving large input and output databases. Zoo provides an intuitive, user-friendly interface for storing, browsing, and retrieving data used and produced by complex models. We demonstrate how a scientist with little or no expertise in database systems can use Zoo to create input and output Databases for Cupid, efficiently view and access the data therein, and easily manage multiple Cupid simulations.

Diqv. A-5 - Environmental Quality

Non-Equilibrium Field-Scale Pesticide Transport: Soil Cores vs. Solution Samplers. T.J. GISH*, K.J.S. KUNG, C.S. HELLING, D. GIMENEZ, and A. SHIRMOHAMMADI. USDA-ARS, Univ. of Wisconsin-Madison, Univ. of Maryland.

Soil cores and solution samples are routinely removed from fields and used to characterize solute transport to ground water underlying agricultural fields. Atrazine, deethyatrazine (DEET) and bromide concentrations were monitored through the top 1.8 m of soil in no-till and tilled fields. Eighteen soil cores were removed throughout the year. These data were compared to results from 144 suction lysimeters sampled after every >10 mm rain event. At early times (<3 wks after application), atrazine and DEET concentrations observed in the soil cores and from solution samplers were not in equilibrium. The greater volume-normalized herbicide concentrations observed in the solution samplers is likely a result of preferential transport.

Div. A-6 - International Agronomy

An Assessment of Soil Quality in a Hillside Agroecosystem of Honduras. P. ERICKSEN* and K. MCSWEENEY, Univ. of Wisconsin-Madison.

Our study was conducted in a catchment (950 ha 2 ) occupied by two communities in the Dep. of Francisco Morazon in central Honduras. The soils are derived from volcanic materials and elevation within the catchment ranges from 1100 to 1850 m. Subsistence agriculture and cattle grazing are the primary activities, although a considerable portion of landscape contains primary and secondary forest of pine and some hardwood. Our objective was to identify and interpret soil landscape processes operating at different scales and under different land uses. We hypothesized that at the catchment scale patterns of land use can be explained by the productive potential and constraints of the land. The mosaic of patches of intensive agricultural-, pasture-, abandoned-land, and primary forest supports the notion that farmers have by trial-and-error matched their land use to the intrinsic variation in the landscape. At the fine or plot scale, a variety of physical, chemical, and biological attributes were measured at 20 sites representing different land uses, to determine if processes active at the sites were contributing to a sustainable or deteriorating state of soil quality. Finally, a semi-quantitative index of soil redistribution within and among patches/plots was used for interpreting the impact of particular land uses on adjoining land and water quality within the catchment.

Div. A-8 - Integrated Agricultural Systems

Soil Quality: Building a Flexible Framework Based on Farmer Input. K. MCSWEENEY*, R.F. HARRIS, P. ERICKSEN, and D. ROMIG, Univ. of Wisconsin-Madison.

We will present a synthesis from several studies conducted with farmers concerning their assessment of soil quality/health. The studies were conducted in Wisconsin, Honduras, and Costa Rica. A major impetus was to establish links between farmers and scientists' perception and knowledge about soil quality as a basis for developing participatory approaches for soil management. Common findings among the studies include: (1) farmers tend to use variety of non-soil attributes (e.g., plant health, water quality) as well as descriptive and analytical attributes for soil quality assessment; (2) spatial and temporal perspectives of soil quality differ among scientists and farmers; the "universe" and purpose that farmers employ for soil quality assessment may be quite different from that of scientists. These and other findings will be presented as considerations for development of frameworks for soil quality assessment that use farmer input.

Computer Software Application Committee

A Soil Fertility Course Website A Prototype, One Year Later. P. BARAK, Univ. of Wisconsin-Madison.

An internet-delivered document on soil fertility was supplemented with on-line syllabus and staff information and real-time class notes, reading assignments, on-line readings, digital photographs, and problem sets to create a soil fertility course website for junior/senior university students. Student comfort and competence levels were assessed at the beginning and end of the semester. Although one-half of students initially indicated discomfort or inexperience with internet, all students but one indicated that they were comfortable or very comfortable with the electronic delivery at the end of the semester. Almost 75% of respondents were likely to favor taking another course with an internet or e-mail component, with all others reporting that it would not alter their decision to enroll. The single greatest difficulty for students was access to the website, either through sometimes-crowded campus microcomputer labs or through dial-in modems to the campus server that were difficult to reach during peak evening hours. The number of instructor-hours devoted to developing and maintaining a course website should not be trivialized. Students gave high marks to instructor's commitment to teaching in final course evaluations.

Div. C-6 - Crop Quality and Utilization

Weather and Alfalfa Quality in Wisconsin. W.L. BLAND*, V.R. KANNEGANTI, and D.J. UNDERSANDER, Univ. of Wisconsin-Madison.

Nutritional quality of forage fed to dairy cows has enormous financial implications for Wisconsin producers. The ability to predict quality in the growing crop is needed for scheduling harvest and to simulate and analyze forage systems. Prediction methods that depend on observations of plant development show promise for harvest management, but are not suited to, simulation. Results of environment-driven attempts at modeling changes in forage quality remain disappointing. A dataset is available in Wisconsin of more than 1000 samplings of alfalfa made by county Extension staff in a program to advise farmers on optimal time of harvest. Data span a 5-yr period, 38 counties, and are typically three to five samples from a site prior to harvest. The ratio ADF/NDF is 0.83 + 0.02 for the majority of samples, although for a few counties this ratio is 0.74 + 0.02 consistently. Change of NDF in time is linear, with slopes varying from 0.2 to 1.1% d -1 ; this slope is unrelated to latitude. A mechanistic simulation model appears to be required for a robust prediction system.

Div. S-1 - Soil Physics

Impact of Funnel-Type Preferential Flow on Sampling. K.J.S. KUNG*, S.H. JU, and C. HELLING, Univ. of Wisconsin-Madison and USDA-ARS.

Soil-solution sampling methods developed over 50 yr ago are still routinely used to monitor fate and breakthrough curve (BTC) of contaminants in unsaturated soils. Conventionally, assumptions have been that: (1) concentration-based BTC (ABTC) and mass-flux based BTC (MBTC) are identical; and (2) BTC from samples (SBTC) would become accurate when enough samples are collected. Numerical simulations were conducted in twelve 2-D hypothetical profiles with funnel flow paths to test the validity of these assumptions. Simulated results indicate that: (1) MBTC ultimately is the most representative leaching pattern to indicate the loading of a contaminant at a certain soil depth; and (2) ABTC always significantly underestimates MBTC. By increasing the total number of randomly located samples, SBTC will never accurately indicate MBTC. The SBTC could be modified to better estimate MBTC when preferential weight is assigned according to the local water flux. However, the SBTC from soil coring methods would always underestimate MBTC.

Frequency-Domain Reflectometry for Water Content Measurement Using a Network Analyzer at Radio Frequencies. G.C. STARR* and B. LOWERY, Univ. of Wisconsin-Madison.

Instrumentation and methodology for an electrodynamic technique called frequency-domain reflectometry (FDR) to measure soil water content using a network analyzer have been evaluated. The approach is similar to time domain reflectometry (TDR), and the same probes are used for each technique. The FDR approach measures dielectric constant to derive water content. Measurements are made of reflected power vs. frequency, and data are transformed by the network analyzer to reflected power vs. effective probe length using an inverse Fourier transform. FDR provided a reliable measure of θ_v in Sparta sand (sandy, mixed, mesic Entic Hapludolls). θ_v was measured from 0.250 to 0.020 m 3 /m 3 , with an accuracy of 0.0015 m 3 /m 3 . A linear calibration of θ_v vs. K a 1/2 ; was found with an r 2 of 0.999. The advantages of FDR for sandy soils are improved signal:noise ratio and better resolution, resulting in greater accuracy and sensitivity. FDR contains a built-in computer that produces simpler waveform analysis and greater versatility in data handling over TDR. The cost of FDR is comparable to that of TDR. The signal:noise ratio is about 250:1.

Measuring Instantaneous Solute Flux and Loading with Time Domain Reflectometry. G.L. HART * and B. LOWERY, Univ. of Wisconsin-Madison.

Time domain reflectometry (TDR) has become a popular method of measuring water content and conservative tracer concentration in soils. We investigated the use of TDR for monitoring variable flux contaminant loading in a rapidly draining sandy soil on a real-time basis. This is feasible because of the ability to acquire rapid, multiplexed measurements of both variables necessary for calculating loading - water flux and resident contaminant concentration. Waveguides for TDR monitoring generally measure small spatial boundaries, allowing the implementation of simplifying assumptions for estimating flux. Results of laboratory experiments conducted under steady-state and transient-flow conditions were compared. Combining data from steady-state and transient-flow experiments, average mass balance recovery ratios of 113% for water and 104% for a bromide tracer were obtained. LEACHM simulations were in good agreement with TDR monitored transient-flow data. Under steady-state conditions, LEACHM was unable to accurately predict pore water velocity. Adjusting the effective porosity lead to quantification of an immobile water content of 0.03 m3 m-3. Use of TDR is envisioned as an excellent means of advancing understanding of transport phenomena.

Div. S-2 - Soil Chemistry

Binding of Mercury (II) in Soil Organic Matter. U. SKYLLBERG* 1 , P. R. BLOOM 1 , E. A. NATER 1 , K. XIA 2 and W. BLEAM 2 , 1 Univ. of Minnesota and 2 Univ. of Wisconsin-Madison.

Natural organic matter (NOM) is a dominant factor behind the retention and mobility of anthropogenic Hg (II) deposited in forested ecosystems. Based on the very high affinity of Hg (II) for R-SH groups, we hypothesize that reduced S sites bind Hg (II) in NOM. To test this, competitive studies between Hg (II) and metals with different affinity for R-SH were combined with XANES (X-ray absorption near edge spectroscopy) and XAFS (X-ray absorption fine structure) studies for a range of NOM samples taken along two upland-wetland transects in northern Minnesota. In Ca and Al nitrate dissolved Hg (II) was due solely to the solubilization of NOM, whereas Cu (II) was found to compete with Hg (II) for binding sites. XANES showed that a wide ratio of reduced to oxidized S occurs in NOM. XAFS of Hg (II) substituted NOM showed that reduced S participates in the Hg (II) bonding in samples with a high ratio of reduced to oxidized S. The strong binding of Hg (II) to reduced S in NOM imply that at present concentrations of Hg (II) in northern forest ecosystems (100 - 500 ng Hg (II) g -1 [NOM]), the mobility of Hg (II) and its transport from soils to surface waters is highly dependent on the solubility of NOM and less dependent on variations in the speciation of mercury (II).

Complexation Constants of Cadmium, Copper, and Zinc with Soil Organic Matter. K. XIA*, P.A. HELMKE, and W.F. BLEAM, Univ. of Wisconsin-Madison.

Trace metals bound to soil humic substances are commonly assumed to be exchangeable. The exchange behavior of Cu. Cd, and Zn bound to soil humic substances was determined in isolation from the effects of soil reactions. The soil humic substances were extracted with Chelex-20 ion exchange resin from a Plano silt loam (Typic Argiudolls) treated with and without sewage sludge. The extracted humic substances were titrated with Cu 2+ , Cd 2+ , Zn 2+ , and Ca 2+ and the equilibrium activities of the trace metals determined by our procedures of Donnan membrane analysis and graphite furnace atomic absorption spectrophotometry. The exchangeability of metals on the extracted soil humic substances increased with metal loading rates.

Ion Transport Measurements in Soils by Use of Custom-Built Ion-Selective Microelectrodes and Computer-Driven Micromanipulator and Data-Logger. L.A. SHERMAN* and P. BARAK, Univ. of Wisconsin-Madison.

Transport of major ions in soils due to processes such as mineral dissolution result in microscopic ion concentration gradients in soils. Ion gradients are usually measured using destructive one-time sampling techniques and measurements limited to planar geometries. Novel ion-selective microelectrodes were constructed to allow measurement of the development of ion gradients in soils over time and gradients of any spatial geometry. Use of a computer-driven xyz micromanipulator and data-logger yields precision placement of electrodes and automated data recording. The transport of major ions due to the dissolution of agliming and fertilizer materials in soils was measured with the microelectrode/micromanipulator system. The soil amendments were placed in contact with a silt loam soil in a custom-built diffusion cell under a controlled temperature and moisture regime. The development of microscopic ion gradients of various geometries was measured with a spatial resolution of 2 mm and on time scales ranging from hours to days.

Role of Metals and Complexing Agents on Mineralization of Soil Organic Phosphorus by Root-Released Enzymes. X. HE and P. A. HELMKE*, Univ. of Wisconsin-Madison.

Up to one-half of the total P in some soils is associated with soil humic substances. The bioavailability of the P associated with soil humic substances depends on processes that mineralize the organically bound P. The interactions of Fe, Al, and trace metals and metal complexing agents exuded by plant roots on the effectiveness of acid phosphatases and phytase to mineralize P bound to soil humic substances were determined. Some metals strongly inhibit P mineralization reactions, but the effect is ameliorated by low concentrations of citric acid. It appears that phytic acid and other P humic substances form insoluble trace metal complexes that are nonreactive with phosphatases but that their reactivity is restored by removing the metals with metal complexing agents.

Effects of Organic Residues and Calcium and Magnesium from Dolomite on Soil Acidity and Activity of Trace Metals. J.A.G. SANTOS*, S. BUZETTI, and P.A. HELMKE, Univ. of Wisconsin-Madison.

The effects of lime and solid (SOR) and liquid organic residues (LOR) from petroleum wastes on soil acidity and exchangeable Ca and Mg were studied under laboratory conditions. Three kilograms of a disturbed Oxisol were treated with (3X) four rates of SOR and two rates of dolomite or three rates of LOR and two rates of dolomite to increase the base saturation to 50 and 100%, plus controls. The addition of 18 g of SOR or 0.285 L of LOR reduced reactive acidity and exchangeable Al as efficiently as adding dolomite to 100% of the base saturation. The total saturation water-extractable concentrations of Cu, Zn, and Cd were determined by ICP-OES and the concentrations of their free ions were determined by Donnan membrane equilibrium to study effects of the treatments on the solubility of trace elements.

Indigenous Free Ion Activity of Zinc as a Function of pH in Water Saturation Extracts of Soils from Brazil, North America, and Australia. P.A. HELMKE*, J.A.G. SANTOS, S. BUZETTI, K. XIA, and R. NAIDU, Univ. of Wisconsin-Madison.

The free ion activity of Zn was determined in water saturation extracts of soils from Brazil, North America, and Australia as a function of pH by our methods of Donnan membrane equilibrium analysis. The indigenous pH of the soils ranged from 5 to 8.5. Typical values of the activity of Zn 2+ in the extracts ranged from 1 to 10 µM. Slopes of the relationship pZn 2+ versus pH (pZn 2+ = a + b·pH) ranged from 0.25 to 0.7. These values are similar to those found by many other researchers for total pZn as a function of pH. A slope of 2.0 is predicted by the hypotheses that the solubility of franklinite (ZnO·Fe 2 O 3 ) controls the solubility of Zn 2+ in soils. The results obtained in this research do not support the franklinite hypothesis.

Div. S-3 - Soil Biology and Biochemistry

Diagram-Assisted Redox Model for Mass Balancing Bioremediation by Microorganisms. R F. HARRIS* and W. J. HICKEY, Univ. of Wisconsin-Madison.

The model is based on sequential derivation of mass balance coefficients for microbial growth (biosynthesis and maintenance) and co-metabolism as a function of assimilatory electron donor, C, N, P, and S nutrients, dissimilatory electron donor and electron acceptor couples, and experimental and theoretical growth yields and metabolic pathways. Use of the model is initiated by entry into a blank electron flow diagram of the empirical molar composition and redox properties of the substrates, biomass and metabolic byproducts of the hypothesized microbial reaction. Derivation of stoichiometric coefficients for the reaction is assisted by reference to the diagram as well as by use of integrated mass balance equations. Provisions for endogenous metabolism, death and cryptic growth are also included. The model is illustrated by application to aerobic trichloroethylene degradation stimulated by methane and ammonium.

Div. S-4 - Soil Fertility and Plant Nutrition

Effect of Calcium and Magnesium Concentrations on the Uptake of Copper, Iron, Manganese and Zinc by Lettuce, Lupin, Soybean, and Wheat. S. BUZETTI*, J.A.G. SANTOS, and P.A. HELMKE, Univ. of Wisconsin-Madison.

The effects of Ca and Mg on the uptake of Cu, Fe, Mn, and Zn by lettuce ( Latuca sativa L.), lupin ( Lupinus albus L), soybean ( Glycine max L. Merrill), and wheat ( Triticum aestivum L.) in hydroponic culture was determined in half-strength Hoagland solution for 28 days with three rates of Ca (0.5, 2.0, and 8.0 mM) and three rates of Mg (0.25, 1.0, and 4.0 mM). The experiment was set up as a completely randomized design in a factorial scheme. Calcium rates influenced soybean growth and the Cu, Fe, Mn, and Zn content of the shoot and root of lettuce and soybean. Variation of the Ca in the solution from 0.5 to 8.0 mM reduced the accumulation of Cu, Fe, Mn, and Zn in soybean and in the accumulation of Mn and Zn in lettuce. Increasing the rate of Mg reduced Cu and Mn in soybean roots and Zn in the lupin and wheat roots.

Influence of Nitrogen Timing and Irrigation Methods for Potatoes. S.A. WILNER*, K.A. KELLING, and L.R. MASSIE, Univ. of Wisconsin-Madison.

Split applications of N fertilizers banded on the row or applied through irrigation systems to potatoes may result in greater uptake efficiencies and lower leaching potentials, especially under precession irrigation methods. This study was designed to determine the effects of four NH 4 NO 3 fertilizer management regimes under trickle or sprinkler irrigation systems on a Plainfield loamy sand (mixed, mesic Typic Udipsamments) at Hancock, Wis. Overall yields for 1995 were about 30% lower than normal and may have been limited by an infestation of Verticillium dahliae , yet some trends appeared evident. In general, sprinkler irrigation produced significantly higher tuber yields than did the trickle system when averaged across fertilizer treatments. Surface banding the N on top of the row, split between emergence, tuberization, and tuberization +15 days resulted in higher tuber yields and quality than when the N was applied by fertigation. Additional splitting of the N did not show any extra benefit. Based on petiole NO 3 -N values, it appears that banded N with the trickle system may have been positionally unavailable early in the growing season but maintained plant N levels longer.

Crop Residue Effects on Nitrogen Availability in No-till Corn. L.G BUNDY* and T.W. ANDRASKI, Univ. of Wisconsin-Madison.

In northern climates, reduced N availability in no-till continuous corn ( Zea Mays L.) frequently occurs. A 3-yr field study was conducted to identify potential mechanisms contributing to reduced N availability in no-till corn and to evaluate management approaches for avoiding N deficiencies. The effects of residue level (0x, 1x, 2x), N rate (0 to 224 kg N ha -1 ), and N source and placement variables on N availability and yield were investigated. Net N mineralization during the early corn growing season decreased as residue levels were increased from 0x to 2x. Artificial (polypropylene) residue and 1x corn residue providing similar soil cover showed similar net N mineralization. Soil temperatures at a 10-cm depth with 0x residue were 4&deg;C higher than with 2x residue, and 2&deg;C higher than both 1x and artificial residue treatments. Corn yields decreased with increasing residue level at 0 and 90 kg ha -1 N rates. Yield response to N sources and placement methods suggests that NH 3 losses from surface-applied urea-containing fertilizers were low. Results indicate that reduced N availability in no-till corn is primarily due to slower N mineralization caused by lower soil temperatures in high residue systems rather than to immobilization of N in residues.

Div. S-5 - Pedology

The NSSC Database for Permafrost-Affected Soils (Gelisols). J.G. BOCKHEIM, J.M. KIMBLE*, C.L. PING, and J.P. MOORE, Univ. of Wisconsin-Madison, NRCS, and Univ. of Alaska.

The National Soil Survey Center database contains 96 pedons with a pergelic soil temperature regime, half of which are classified as Pergelic, Histic Pergelic, or Pergelic Ruptic-Histic Cryaquepts. Eighty of the pedons satisfy the requirements of the new Gelisol order (gelic material and permafrost within 100 to 200 cm of the surface) and represent 12 of the 20 great groups. Only seven of the Gelisol pedons have an active layer (depth of seasonal thawing) deeper than 100 cm (the average depth = 49 cm). More than two-thirds of the pedons feature cryoturbation (frost churning), which is used to distinguish mineral soils at the suborder level. Although more than half (58%) of the pedons have an aquic soil moisture regime, the thickness of the organic layer is used as the first cut to distinguish Gelisols at the great-group level. The organic layer thickness is highly correlated (p = 0.006) with active layer thickness.

Soil Studies in the Lower Kolyma River Area, Far Eastern Russia. J. M. KIMBLE* 1 , C. TARNOCAI 2 , J. BOCKHEIM 3 , C.L. PING 4 , AND S. SMITH 2 . 1 USDANRCS-NSSC, 2 Agri. and Agri-Food Canada, Ottawa, 3 Univ. of Wisconsin-Madison, 4 Univ. of Alaska, Fairbanks.

A joint mapping and soil characterization project was carried out in the far North Eastern part of Russia in 1994 near Cherskiy. The area is largely unglaciated with a strongly continental climate. The MAAT is about -13&deg;C, with an annual precipitation of 220 to 240 mm. Field samplings and mapping were carried out in three different areas: Rodinka Mountain, characterized by frost-shattered bedrock and residuum under alpine vegetation; Duvanny Yar, which is an exposure of silt and syngenetic ice complexes along the Kolyma River; and the Kurishka Tundra, which was on the coastal tundra zone of the East Siberian Sea. Characterization data along with the soil maps are presented. There was a major lack of cryoturbation as compared to similar areas in Canada. Relationships between Soil Taxonomy, the Canadian and Russian taxonomic systems are discussed.

Development of a Three-Dimensional Soil-Landscape Model for the Loess Mantled Region of Southwestern Wisconsin. P.K. FALK*, K. MCSWEENEY, and S.J. VENTURA, Univ. of Wisconsin-Madison.

The loess-mantled ridge and valley topography of the Driftless Area in southwestern Wisconsin constitutes a fragile environment that is strongly controlled by the underlying bedrock. We will present a three-dimensional soil-landscape model, which incorporates geostatistical analysis of data at both fine and coarse scales. Attributes used in the model fall into five categories: attributes related to topography, soil physical properties, soil chemical properties, microclimate, and vegetation. Initial results indicate amounts of phosphorus and potassium are lower on south-facing than north-facing slopes. In addition, cultivation provides marked local variation in amounts of these attributes at finer scales. The addition of past land use history, soil biota and vegetation to the model provides additional characterization of this human modified ecosystem, and potentially, additional explanation of soil forming processes.

Micromorphological Alterations of Soils Under Long-Term Contrasting Prairie Management Systems. K.L. MALTONI*, UNESP/Ilha Solteira, Brazil, K. MCSWEENEY, Univ. of Wisconsin-Madison, and G. LEMASTERS, Dep. of Agric. Resource Management.

Five contrasting prairie management treatments were established at three sites at the University of Wisconsin Arboretum in 1940, 1950, and 1956. The treatments consist of 'restored', 'burned', 'harvested', 'mulched', and 'bare'. We investigated the impact of biomass management on surface soil structure. The 'restored' treatment has developed a strongly aggregated structure. The structure of the 'burned' treatment closely resembles that of the 'restored' treatment, but shows some evidence of platyness. The remaining treatments all exhibit platy structure and associated vesicular porosity, which is most strongly expressed in the bare treatment. The bare treatment has a strongly developed surface seal. We attribute the platy structure to repeated cycles of freeze/thaw and wet/dry. Evidence of incorporated biomass and earthworm activity in the soils decreased as follows: harvested, mulched, bare, which is matched by an increase in area of platy structure. Reduced biological activity appears to be associated with the persistence of platy structure in these treatments.

Div. S-6 - Soil and Water Management and Conservation

Carbon and Nitrogen Cycling on an Ecosystem Gradient from Cultivated Corn to Natural Prairie. KR. BRYE*, J.M. NORMAN, L.G. BUNDY, and S.T. GOWER, Univ. of Wisconsin-Madison.

A study was undertaken to evaluate, characterize, and model various components of the C and N cycles of several common and historic land use patterns of Wisconsin (e.g., chisel plow and no-till corn, and natural prairie). The ecosystems under investigation reside on a silt loam soil with similar edaphic properties and morphological characteristics. In April 1995, initial total soil C and organic matter content for the top 3-cm layer were the same in all ecosystems. Nitrate leaching and drainage were quantified in the field usimg suction plate Iysimeters. The chisel plowed corn ecosystem had greater cumulative drainage from July 1995 through May 1996 than the other two ecosystems, where the prairie's drainage was 10 times less than that measured under cultivation. Cumulative, post-growing season NO 3 - leaching losses between October 1995 and April 1996 were 12.4, 7.4, and <0.05 kg NO 3 -N ha -1 for the chisel plow, no-till, and prairie systems, respectively. The differences in NO 3 - leaching can be attributed to decreasing drainage and substantially lower soil solution NO 3 - concentrations for the prairie ecosystem. These results confirm the environmental concern over groundwater contamination by nitrates associated with production agriculture.

Div. S-8 - Nutrient Management and Soil and Plant Analysis

Selenium and Trace Metals in Forage Samples. L.S. ZHANG* and S.M. COMBS, Univ. of Wisconsin-Madison/Extension.

The quality of forage samples was surveyed in terms of selenium concentration, other major, minor and trace metal concentrations, and concentrations of other components such as crude protein, acid detergent fiber and neutral detergent fiber. The concentrations of selenium and other major, minor, and trace components were measured with hydride generation inductively coupled plasma mass spectrometry after the samples were digested with nitric acid and hydrogen peroxide. The selenium concentration in these samples ranged between 0.82 and 0.03 mg kg -1 with an average of 0.13 + 0.12 mg kg -1 . The relationship between selenium concentration and concentrations of other components were sought.

Determination of Dissolved Organic Carbon by Inductively Coupled Plasma Mass Spectrometry. S.M. COMBS, L.S. ZHANG*, and Y.J. LIU, Univ of Wisconsin-Madison/Extension.

Inductively coupled plasma mass spectrometry was applied in the determination of dissolved organic carbon (DOC) in aqueous samples. Samples were passed through 0.45 µ m nitrocellulose filter. Inorganic carbon was removed by purging samples with N2 gas after samples were acidified to ~pH 1 with nitric acid. Volatile DOC was also removed. A carbon standard was made from sucrose. As listed below, 12 C and 13 C can be used to measure DOC in low and high concentration ranges respectively. The background equivalent concentration (BEC) of 12 C was 10 times higher than its limit of detection (LOD). This high BEC might result from atmospheric carbon and/or residual carbon in argon gas. Relative to the determination of DOC by dichromate method, the ICP-MS method is more rapid, easier, has an improved detection limit, a broader dynamic range, and a more complete recovery of DOC.

Designing Soil Test Recommendations to Meet Multiple Goals-Production, Economic, Environmental. K.A. KELLING* and S.M. COMBS, Univ. of Wisconsin-Madison.

Soil tests are an index of nutrient availability for the field sampled. Historically, soil test results have guided fertilizer applications to help meet the production goals of the farmer. As the research base supporting these soil tests increased, the sophistication of Interpretation, including rate considerations and economic evaluation, were increasingly incorporated into recommendations. Additional factors such as soil yield potential, crop to be grown, previous crop, tillage system, method of fertilizer application, years for recommendation and expected crop value have also been included at various times and places. Although computers have allowed test interpretation to accept this complexity, site-specific calibration and obtaining sufficient input information have resulted in compromises for most systems. Attempts are being made today to use soil tests for other purposes, including environmental nutrient management and regulation. Heretofore, research has guided test acceptability and applicability for production and economic goals. As demonstrated by recent research with soil P tests, routine field testing may need to be modified for environmental interpretations.