Abstract Writing
An abstract is a mini version of a paper. It should be the shortest possible.
This
is the shortest abstract ever written
E=m.c2
Exercise:
How
should an abstract be written?
Work with a partner and try to write true or false next to the following sentences,
An abstract
1) should state the principle objectives and scope of the investigation
2) should not describe the methods employed
3) should summarize the results
4) should not state the principal conclusion
5) should be written in the Present Continuous tense because it refers mostly to work being done at present.
6) Should not exceed 450 words.
7) Should cite references to the literature used.
Analyze
the following abstracts and try to find the lines correspondiing to the
Introduction, Methods and materials, Results, and Discussion. (IMRAD)
The annual American Society of Agronomy/Crop Science Society
of
America/Soil Science Society of America meetings were held
Nov. 3-8 in
Indianapolis, Indiana. Over 20 department faculty, staff and
students
participated in oral presentations and poster sessions. The
following is a list of titles with links to the full abstract and author home
page (where available).
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, 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 ha2) 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.
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 [Image]v in Sparta sand (sandy,
mixed, mesic Entic Hapludolls). [Image]v was measured from 0.250
to 0.020 m3/m3, with an accuracy of 0.0015 m3/m3. A linear
calibration of [Image]v vs. Ka1/2; was found with an r2 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.
BLOOM1, E. A. NATER1, K. XIA2 and W. BLEAM2, 1Univ. of Minnesota and 2Univ.
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 Cu2+, Cd2+,
Zn2+, and Ca2+ 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 Zn2+ in the extracts ranged
from 1 to 10 µM. Slopes of the relationship pZn2+ versus pH
(pZn2+ = 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·Fe2O3) controls the
solubility of Zn2+ 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 NH4NO3 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 NO3-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°C higher
than with 2x residue, and 2°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 NH3
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. TARNOCAI2, J. BOCKHEIM3, C.L. PING4, AND S. SMITH2.
1USDANRCS-NSSC, 2Agri. and Agri-Food Canada, Ottawa, 3Univ. of
Wisconsin-Madison,4Univ. 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°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 NO3- leaching losses between October 1995 and
April 1996 were 12.4, 7.4, and <0.05 kg NO3-N ha-1 for the chisel
plow, no-till, and prairie systems, respectively. The differences
in NO3- leaching can be attributed to decreasing drainage and
substantially lower soil solution NO3- 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, 12C and 13C can be used to measure DOC
in low and high concentration ranges respectively. The background
equivalent concentration (BEC) of 12C 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.
12C 13C 12C 13C
Dynamic range mg 1-1 5-2000 20-16,000 BEC mg 1-1 17 20
Precision (%) < 3 < 3 LOD mg 1-1 1.5 5
Designing Soil Test Recommendations to Meet Multiple GoalsProduction,
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.
1996 Agronomy Abstracts | Department Home Page