Source: PURDUE UNIVERSITY submitted to
TRACE ELEMENT CHEMISTRY IN SOILS AND PLANTS
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
TERMINATED
Funding Source
Reporting Frequency
Annual
Accession No.
0090315
Grant No.
(N/A)
Project No.
IND050083
Proposal No.
(N/A)
Multistate No.
(N/A)
Program Code
(N/A)
Project Start Date
Oct 1, 2002
Project End Date
Sep 30, 2007
Grant Year
(N/A)
Project Director
Schulze, D. G.
Recipient Organization
PURDUE UNIVERSITY
(N/A)
WEST LAFAYETTE,IN 47907
Performing Department
AGRONOMY
Non Technical Summary
Some soil trace elements like Mn, Cu, and Zn are essential for plants and animals, while others like Pb, Cr, and Cd are potentially toxic. This project addresses: (1) the interaction of soil manganese and plant fungal diseases, (2) the impact of spatial distribution on trace metal availability, and (3) the role of organic acids in making phosphorus and other trace elements more available to plants.
Animal Health Component
50%
Research Effort Categories
Basic
50%
Applied
50%
Developmental
(N/A)
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
1020110200050%
1020110204050%
Knowledge Area
102 - Soil, Plant, Water, Nutrient Relationships;

Subject Of Investigation
0110 - Soil;

Field Of Science
2000 - Chemistry; 2040 - Mineralogy;
Goals / Objectives
1. Determine if there are large-scale trends in plant-available soil Mn that correlate with particular crop rotations, weather conditions, or the severity of certain plant fungal diseases and, if so, whether these trends correlate with commonly observed allopathic or crop rotation effects. 2. Quantify the microscale spatial distribution of trace element concentrations and mineralogy in uncontaminated soils and in soils contaminated by anthropogenic activities, and correlate the observed distributions with bulk trace element availability. 3. Determine the impact of soil mineralogy on the release of soil phosphorus and other nutrient elements by organic acids commonly exuded by the roots of phosphorus-efficient crop plants.
Project Methods
The work will utilize both bulk wet chemical procedures and advanced x-ray based techniques in the laboratory, with appreciable field sampling of soils in Indiana and Kenya. The synchrotron-based studies will be done at the National Synchrotron Light Source, Brookhaven National Laboratory, and at the Advanced Photon Source, Argonne National Laboratory. Specific Procedures: 1. Soil samples will be collected at four-week intervals during the growing season in corn-soybean-wheat rotations on four representative soils from Indiana. The severity of the take-all disease will be determined for those plots planted to wheat and weather data will be obtained from nearby weather stations. Plant available Mn will be determined by a sequential extraction procedure and the population of Mn-oxidizing organisms will be determined by a microbial Mn-oxidation assay. 2. Selected contaminated and uncontaminated soils will be prepared by imbedding samples in epoxy resin and preparing thin sections. The thin sections will first be studied and photograph using visible light microscopy. The major element distributions of selected areas will then be measured by electron probe microanalysis (at Purdue). Finally, trace element distributions over the same areas will then be measured using x-ray fluorescence spectroscopy (at the National Synchrotron Light Source, NSLS). Micro x-ray diffraction analysis (NSLS) will be used to identify the specific mineral phases present in the areas analyzed by the other techniques. This will allow us to obtain quantitative information at spatial resolutions as small as 10 x 10 micrometers. This information will then be combined with bulk chemical extraction data for the same samples in order to determine how microscale spatial variations in trace element content and mineralogy influence bulk trace element availability. 3. Soils with low plant-available phosphorus will be sampled in Kenya in areas where research plots will be established for plant breeding work. The bulk soil mineralogy of these soils will be determined in the laboratory at Purdue using established procedures for x-ray diffraction analysis of soil materials. Standard bulk chemical techniques will be used to measure extractable P, K, Na, Ca, Mg, and Al. A new extraction technique designed to measure P and Al extractable by citric acid will be developed in cooperation with Dr. Johnston, and will be used to analyze the samples.

Progress 10/01/02 to 09/30/07

Outputs
OUTPUTS: In this final report, we summarize the most significant outputs of this project. Objective 1: We conducted a 2-year study to evaluate the effects of crop rotation and tillage on available soil Mn on plots near West Lafayette, IN. Samples were taken under continuous corn [Zea mays (L.)], continuous soybean [Glycine max (L.)], and corn-soybean-wheat [Triticum aestivum (L.)] rotations under no-till tillage and fall chisel tillage systems at 1-month intervals during the growing season. Mn was extracted using a 3-step sequential extraction using 1M ammonium acetate at pH 7, 1M ammonium acetate at pH 3, and 0.018M quinol in 1M ammonium acetate at pH 7. Extracts were analyzed by atomic adsorption spectroscopy. Objective 2: We analyzed the microscale spatial distribution of various metals in a wet, peaty soil contaminated with Pb, Zn, Cr, and Cd by industrial activity. We used a binocular microscope to select aggregates 100 to 200 um in diameter that had distinctive morphologies and appeared to be inorganic, and a synchrotron x-ray microprobe to obtain micro x-ray diffraction patterns and x-ray fluorescence (XRF) patterns of each aggregate. Total chemical analysis of the bulk samples was quantified by x-ray fluorescence spectroscopy. Scanning electron microscopy was used to examine selected aggregates. Objective 3: Our work is part of a much larger project aimed at enhancing the phosphorus uptake efficiency and aluminum tolerance of field crops for use in developing countries. We conducted the soil characterization work and obtained chemical, x-ray diffraction, transmission electron microscopy (TEM), scanning electron microscopy (SEM), and other data for representative agricultural soils from the maize growing regions of Kenya and the Brazilian Cerrado. The results of our work have been disseminated by publication in peer reviewed journals, theses, abstract volumes, and by oral and poster presentation at national and international conferences. Three graduate students were trained during this project. PARTICIPANTS: D. G. Schulze, Agronomy Dept., Purdue University, PI. D. M. Huber, Botany and Plant Pathology Dept., Purdue University, Co-PI. C. T. Johnston, Agronomy Dept., Purdue University, Co-PI. A. P. Schwab, Agronomy Dept., Purdue University, Co-PI. M. K. Banks, Civil Engineering Dept, Purdue University, Co-PI. R. Schaffert, Embrapa Maize and Sorghum, Sete Lagoas, Brazil, Co-PI. R. Okalebo, Dept. of Soil Science, Moi University, Eldoret, Kenya, collaborator. C. Othenio, Dept. of Soil Science, Moi University, Eldoret, Kenya, collaborator. S. Gudo, Dept. of Crop Science, Moi University, Eldoret, Kenya, collaborator. W. C. Smith, M.S. student, Purdue University. X. D. Gao, Ph.D. student, Purdue University. P. A. Obura, Ph.D. student, Purdue University. The three students listed above were trained during this project. TARGET AUDIENCES: Soil Scientists and Soil Chemists

Impacts
Objective 1. Crop rotation had significant effects on Mn extracted with 1M ammonium acetate at pH 7, with continuous corn showing the highest extractible Mn in both years, and continuous soybean the lowest. Soybean, wheat, and corn in rotation were not significantly different in either year, and tillage did not significantly change extractable Mn in either year. The crop, therefore, can significantly alter the plant available Mn of the soil in which it is grown, and explains why Mn deficiency is uncommon under corn, but occurs frequently under soybean. This was W. C. Smith's thesis project and he completed his M.S. degree in January, 2007. Objective 2: Our work showed just how very complex the chemical and mineralogical speciation can be in soils contaminated by metals from industrial activities. Using synchrotron micro x-ray diffraction, we were able to identify a number of phases that were not readily identified using traditional bulk diffraction patterns. Since the horizons >50 cm deep were saturated and reduced year round, there was a distinct pattern of minerals with depth. Oxides and hydroxides of iron predominated near the surface (<20 cm depth), with oxidized arsenic [As(V)] presumably sorbed to the iron oxide minerals. At depths >50 cm, sulfides of iron, lead, arsenic, and zinc were the most abundant phases. From 20 - 50 cm, phases like magnetite (Fe3O4), that contain both oxidized and reduced forms of iron, were found. The sequence of minerals is that which one would expect from thermodynamic considerations. The complex assemblage of minerals makes soils like this difficult to remediate in situ, and explains why disturbing the soil during a remediation procedure could release more metals to the environment than simply keeping the soil in place. This was X. D. Gao Ph.D thesis project and he completed his degree in March, 2007. Objective 3: The clay fraction of all of the soils is predominately kaolinite or halloysite, while gibbsite, mica, and expandable 2:1 minerals occur as minor phases in some soils. Kenyan soils east of the Rift Valley that were developed on volcanic parent materials have significantly higher exchangeable Al and contain significant gibbsite, while soils west of the Rift Valley formed on weathered igneous and metamorphic rocks and have much lower extractable Al and negligible gibbsite. This explains why soils east of the Rift Valley had significantly higher phosphorus sorption capacities than soils west of the Rift Valley. TEM showed that the 1:1 clay mineral is best described as halloysite, or as a mixture of kaolinite and halloysite, but not as kaolinite. SEM showed the presence of a Na-rich primary mineral in the sand fraction of all of the soils, and explains why exchangeable Na is much higher than expected. The clear differences in the soils east and west of the Rift Valley means that different fertility practices will probably need to be developed for each group of soils. In addition, the germplasm developed by our crop science colleagues on this project will likely respond differently to the two groups of soils. This was Pamela Obura's thesis project and she will complete her degree in January, 2008.

Publications

  • Eugene, B., B. Joern, C. Johnston, and D. Schulze. 2006. Interaction of organic and inorganic P on iron and aluminum oxides and kaolinite. Abstracts, Soil Science Society of America Annual Meetings, November 12-16, 2006, Indianapolis, IN. CD-ROM.
  • Gao, X. D. 2007. Speciation and geochemical cycling of lead, arsenic, chromium, and cadmium in a metal-contaminated Histosol. Ph.D. thesis, Agronomy Dept., Purdue University, West Lafayette, IN. 227 p.
  • Smith, W. C. 2007. Crop rotation and sequence influence on soil manganese availability. M.S. Thesis, Agronomy Dept., Purdue University, West Lafayette, IN. 74 p.
  • Azevedo, A. C., and D. G. Schulze. 2007. Aggregate distribution, stability and release of water dispersible clay in two subtropical Oxisols. Sci. Agric. (Piracicaba, Braz.), 64:36-43.
  • Gao, X. D., and D. G. Schulze. 2006. Speciation and geochemical cycling of lead, arsenic, chromium, and cadmium in a smelter-contaminated soil. Abstracts, Soil Science Society of America Annual Meetings, November 12-16, 2006, Indianapolis, IN. CD-ROM.
  • Obura, P., D. G. Schulze, C. T. Johnston, J. R. Okalebo, and C. Othieno. 2006. Chemistry and mineralogy of selected Kenyan acid soils. Abstracts, Soil Science Society of America Annual Meetings, November 12-16, 2006, Indianapolis, IN. CD-ROM.


Progress 10/01/05 to 09/30/06

Outputs
Work on objective 2 continued as we analyzed a wet, peaty soil contaminated with Pb, Zn, Cr, and Cd. We used a binocular microscope to select aggregates 100 to 200 um in diameter that had distinctive morphologies and appeared to be inorganic, and a synchrotron x-ray microprobe to obtain micro x-ray diffraction patterns and x-ray fluorescence (XRF) patterns of each aggregate. Oxidized phases of Fe and S, [akaganeite (FeOOH), goethite (FeOOH), gypsum (CaSO4*2H2O)] occur in the oxidized surface layers at 0-20 cm depth. Pb and As are apparently sorbed on Fe oxides in these layers because separate Pb- and As-phases have not been identified, but Pb and As are abundant in the XRF patterns. Siderite (FeCO3) and magnetite (Fe3O4) occur frequently at 20-50 cm depth, suggesting redox potentials of this layer sufficient to reduce Fe, but not S. Phases containing reduced S and the contaminant metals were found in the highly reduced layers at >50 cm depth. Galena (PbS), realgar (AsS), alacranite (As4S4), sphalerite (ZnS), arsenopyrite (FeAsS), mackinawite (FeS) have been identified, but separate Cr and Cd phases have not been found. X-ray absorption near edge structure (XANES) spectroscopy showed that arsenic occurs as As(V) in the 0-20 cm layer, as a mixture of As(V) and As(III) in the 20-50 cm layer, and as As(III) in the >50 cm layer, consistent with the phases identified by XRD. Total chemical analysis of the bulk samples was quantified by x-ray fluorescence spectroscopy. Scanning electron microscopy of selected aggregates shows that some of the aggregates are probably of biological origin. Work on objective 3 focused on obtaining chemical and x-ray diffraction data for representative agricultural soils from the maize growing regions of Kenya and the Brazilian Cerrado. These soils have very low extractable phosphorus, low base saturation, low effective cation exchange capacity (ECEC) and moderate to high organic matter. The clay fraction of all of the soils is predominately kaolinite or halloysite, while gibbsite, mica, and expandable 2:1 minerals occur as minor phases in some soils. Soils east of the Rift Valley in Kenya have significantly higher exchangeable Al and contain significant gibbsite, while soils west of the Rift Valley have much lower extractable Al and negligible gibbsite. Soils from the Brazilian Cerrado region tend to have significantly higher gibbsite contents than soils from Kenya.

Impacts
Manganese is a plant-essential micronutrient. Our research shows that the crop itself alters the amount of manganese available for plant uptake. If we can determine the mechanism by which this occurs, it might be possible to breed crops that are more efficient in obtaining manganese from the soil, thus reducing yield losses associated with manganese deficiency. Soils contaminated with potentially toxic metals are a significant environmental problem at many industrial and military sites. If we can understand the chemical forms of these metals in soils, we hope to develop cost-effective soil amendments that will sequester these metals in chemical forms that are not taken up by plants and animals, thus reducing the impact of these metals on the environment. Although an overabundance of plant nutrients such as nitrogen and phosphorus is a serious environmental concern in many industrialized countries, farmers in many countries of the developing world still grow food crops with little or no fertilizer. Our work in Kenya is part of a larger project that has the goal of increasing the phosphorus uptake efficiency of field crops on acid savannah soils. If successful, it will increase food security in some of the poorest countries of the world.

Publications

  • Thompson, I. A., D. M. Huber, and D. G. Schulze. 2006. Evidence of a multicopper oxidase in Mn oxidation by Gaeumannomyces graminis var. tritici. Phytopathology 96: 130-136.
  • Yau, K. P, D. G. Schulze, C. T. Johnston, and S. L. Hem. 2006. Aluminum hydroxide adjuvant produced under constant reactant concentration. J. Pharm. Sci. 95:1822-1833.


Progress 10/01/04 to 09/30/05

Outputs
Work on objective 1 was largely completed this year. We conducted a 2-year study to evaluate the effects of crop rotation and tillage on available soil Mn on plots near West Lafayette, IN. Samples were taken under continuous corn [Zea mays (L.)], continuous soybean [Glycine max (L.)], and corn-soybean-wheat [Triticum aestivum (L.)] rotations under no-till tillage and fall chisel tillage systems at 1-month intervals during the growing season. Mn was extracted using a 3-step sequential extraction using 1M ammonium acetate at pH 7, 1M ammonium acetate at pH 3, and 0.018M quinol in 1M ammonium acetate at pH 7. Extracts were analyzed by atomic adsorption spectroscopy. Crop rotation had significant effects on Mn extracted with 1M ammonium acetate at pH 7, with the continuous corn showing the highest extractible Mn with a back-transformed Least Squares Mean (LSM) of 13.1 mg Mn kg-1 soil for 2002, and 15.7 mg kg-1 for 2003. Continuous corn had more extractible Mn than all other treatments in both years. Continuous soybean had the lowest extractible Mn, with 4.5 mg kg-1 in 2002 and 7.5 mg kg-1 in 2003. Soybean, wheat, and corn in rotation were not significantly different in either year, and tillage did not significantly change extractable Mn in either year. The crop, therefore, can significantly alter the plant available Mn of the soil in which it is grown. Work on objective 2 continued as we analyzed a wet, peaty soil contaminated with Pb, Zn, Cr, and Cd. We used a binocular microscope to select aggregates 100 to 200 um in diameter that had distinctive morphologies and appeared to be inorganic, and a synchrotron x-ray microprobe to obtain micro x-ray diffraction patterns and x-ray fluorescence (XRF) patterns of each aggregate. Oxidized phases of Fe and S, [akaganeite (FeOOH), goethite (FeOOH), gypsum (CaSO4*2H2O)] occur in the oxidized surface layers at 0-20 cm depth. Pb and As are apparently sorbed on Fe oxides in these layers because separate Pb- and As-phases have not been identified, but Pb and As are abundant in the XRF patterns. Siderite (FeCO3) and magnetite (Fe3O4) occur frequently at 20-50 cm depth, suggesting redox potentials of this layer sufficient to reduce Fe, but not S. Phases containing reduced S and the contaminant metals were found in the highly reduced layers at >50 cm depth. Galena (PbS), realgar (AsS), alacranite (As4S4), sphalerite (ZnS), arsenopyrite (FeAsS), mackinawite (FeS) have been identified, but separate Cr and Cd phases have not been found. Work on objective 3 focused on obtaining chemical and x-ray diffraction data for representative Kenyan agricultural soils. These soils have very low extractable phosphorus, low base saturation, low effective cation exchange capacity (ECEC) and moderate to high organic matter. The clay fraction of all of the soils is predominately kaolinite or halloysite, while gibbsite, mica, and expandable 2:1 minerals occur as minor phases in some soils. Soils east of the Rift Valley have significantly higher exchangeable Al and contain significant gibbsite, while soils west of the Rift Valley have much lower extractable Al and negligible gibbsite.

Impacts
Manganese is a plant-essential micronutrient. Our research shows that the crop itself alters the amount of manganese available for plant uptake. If we can determine the mechanism by which this occurs, it might be possible to breed crops that are more efficient in obtaining manganese from the soil, thus reducing yield losses associated with manganese deficiency. Soils contaminated with potentially toxic metals are a significant environmental problem at many industrial and military sites. If we can understand the chemical forms of these metals in soils, we hope to develop cost-effective soil amendments that will sequester these metals in chemical forms that are not taken up by plants and animals, thus reducing the impact of these metals on the environment. Although an overabundance of plant nutrients such as nitrogen and phosphorus is a serious environmental concern in many industrialized countries, farmers in many countries of the developing world still grow food crops with little or no fertilizer. Our work in Kenya is part of a larger project that has the goal of increasing the phosphorus uptake efficiency of field crops on acid savannah soils. If successful, it will increase food security in some of the poorest countries of the world.

Publications

  • Thompson, I. A., D. M. Huber, C. A. Guest, and D. G. Schulze. 2005. Fungal manganese oxidation in a reduced soil. Environmental Microbiology. 7:1480-1487.


Progress 10/01/03 to 09/30/04

Outputs
Progress on objective 1 was slowed this year because of a major illness. Nevertheless, the samples collected during the second year of cropping have now been analyzed for extractable Mn and the data are currently being analyzed to determine if the trends observed in year one and described in last year's report show up in year two. Most of our work on objective 2 focused on a soil contaminated with Pb, Zn, Cr, and Cd from a site receiving runoff from a spoil pile from a former lead smelter. The soil consists primarily of peat (organic soil material). When we examined the soil under a binocular microscope we saw numerous grains of material that appeared distinctly different from most of the soil material. Some of these appeared to be iron oxide accumulations, probably accumulated around the roots of the reeds that grow on the site. Others were black grains that were distinctly different and had a vesicular morphology. We expected to find goethite (FeOOH), and we did in many of the grains. Goethite is a common iron oxide in oxidized soil environments. However, we also tentatively identified akageneite, which generally requires high chloride concentrations for its formation and is not a phase that we would have expected. Gypsum (CaSO4.2H2O) was also present, probably as a result of sulfate leaching from the spoil piles. Even more interesting was the identification of phases containing reduced iron and sulfur. Siderite (FeCO3), greigite (Fe3S4), and (tentatively) wustite (FeO) are all minerals that form in reduced environments. This particular site, therefore, contains minerals that require widely different redox conditions for their stability. As redox conditions change in the soil over the course of the year, it is likely that contaminant metals such as Pb shuttle between different phases. For example, Pb could be tied up as a Pb-sulfide phase under reduced conditions, but could occur sorbed onto iron oxides under oxidizing conditions. This could have important implications for the bioavailability Pb and other transition metals and the management of contaminated sites that have fluctuating soil water tables during the year. Work on objective 3 this year focused on fractionating the Kenyan soils for mineralogical analysis and on analyzing them for cation and anion exchange capacity. We purchased a new, state-of-the-art x-ray diffractometer that will be important for our work on objectives 2 and 3 next year.

Impacts
Manganese deficiency is a common problem in soybeans, wheat, barley, and oats in some areas of Indiana, particularly on the black, sandy soils of the Kankakee River Valley in northwestern Indiana, and on the depressional, heavy-textured soils formed on clay loam glacial till in northeastern Indiana. To correct Mn deficiencies, producers currently use acid-forming fertilizers or apply foliar applications of Mn after symptoms are observed. If we can understand the mechanism by which Mn deficiency occurs, it may be possible to develop approaches that will allow plant breeders to develop plant varieties that are less susceptible to Mn deficiency. Effective bioremediation of contaminated sites requires information on the mineral phases that contain the contaminants. Our work showing that the minerals occurring together in a contaminated site cannot possibly all be stable under the same environmental conditions will allow us to design more effective remediation procedures for the site.

Publications

  • Li, H., L. S. Lee, D. G. Schulze, and C. A. Guest. 2003. Role of soil manganese in the oxidation of aromatic amines. Environ. Sci. Technol. 37:2686-2693.
  • Marques, J. J., D. G. Schulze, N. Curi, and S. A. Mertzman. 2004. Major element geochemistry and geomorphic relationships in Brazilian Cerrado soils. Geoderma 119:179-195.
  • Marques, J. J., D. G. Schulze, N. Curi, and S. A. Mertzman. 2004. Major element geochemistry and geomorphic relationships in Brazilian Cerrado soils. Geoderma 121:31-43.
  • Gomes, J. B. V., N. Curi, P. E. F. Motta, J. C. Ker, J. J. G. S. M. Marques, and D. G. Schulze. 2004. Analise de componentes principais de atributos fisicos, quimicos e mineralogicos de solos do bioma Cerrado. R. Bras. Ci. Solo 28:137-153.
  • Gomes, J. B. V., N. Curi, D. G. Schulze, J. J. G. S. M. Marques, J. C. Ker, and P. E. F. Motta. 2004. Mineralogia, morfologia e analise microscopica de solos do bioma Cerrado. R. Bras. Ci. Solo 28:679-694.


Progress 10/01/02 to 09/30/03

Outputs
We have made progress on all three objectives of this project over the past year. On objective 1, our first full year of data is beginning to show consistent trends in extractable soil Mn under different cropping systems. We are using a sequential extraction procedure consisting of (1) 1 M ammonium acetate at pH 7, (2) 1 M ammonium acetate at pH 3, and (3) 0.018 M quinol in 1 M ammonium acetate at pH 7. All 3 extractable Mn fractions tend to be lowest under soybean, highest under corn, and intermediate under corn-soybean rotations. Thus, there is evidence that the crop itself modifies the soil availability of this important plant micronutrient element. The trends in extractable soil Mn correlate well with field observations in that Mn deficiencies occur frequently in soybean, but only rarely in corn. On objective 2, we have successfully stained soil microorganisms in a contaminated soil with the fluorescent dye calcofluor white (CFW), impregnated the soil with an epoxy resin, and prepared 30 micrometer thin sections. This allowed us to photograph the location of the microorganisms under ultraviolet light. We then used micro x-ray fluorescence and micro x-ray absorption spectroscopy to map the location of lead chromate (PbCrO4) particles that contain potentially toxic Pb and Cr. We found that the microorganisms grew just as well on the PbCrO4 surfaces as on presumably less toxic aluminosilicate mineral surfaces. X-ray absorption spectroscopy showed that the Cr was present in the Cr6+ oxidation state, an oxidation state normally considered to be extremely toxic. Although both Pb2+ and Cr6+ are toxic when available in solution, in combination they form very insoluble PbCrO4, which lowers the solubility of both elements to the nanomoler range, too low to be acutely toxic to soil microorganisms. On objective 3, we spent 2 weeks in the field describing and sampling 11 soils in major agricultural areas in western and central Kenya. The upper two soil horizons of each soil were analyzed for plant-available nutrients, pH, Al saturation, and the results sent to our Kenyan colleagues to allow them to select sites for field experiments.

Impacts
Manganese deficiency is a common problem in soybeans, wheat, barley, and oats in some areas of Indiana, particularly on the black, sandy soils of the Kankakee River Valley in northwestern Indiana, and on the depressional, heavy-textured soils formed on clay loam glacial till in northeastern Indiana. To correct Mn deficiencies, producers currently use acid-forming fertilizers or apply foliar applications of Mn after symptoms are observed. If we can understand the mechanism by which Mn deficiency occurs, it may be possible to develop approaches that will allow plant breeders to develop plant varieties that are less susceptible to Mn deficiency. Effective bioremediation of contaminated sites requires information on the impacts of various pollutants on microbial populations. Our study shows that in a waste site contaminated with both Pb and Cr, the potentially toxic metals are in a chemical form that is very insoluble and apparently has a minimal impact on microbial growth.

Publications

  • Marques, J. J., W. G. Teixeira, D. G. Schulze, and N. Curi. 2002. Mineralogy of soils with unusually high exchangeable Al from the western Amazon Region. Clay Miner. 37:651-661.


Progress 10/01/01 to 09/30/02

Outputs
It is well known that the more soluble forms of contaminant metals are acutely toxic to soil microorganisms. What is not well understood, however, is whether or not less soluble forms of contaminant metals impact the distribution of microorganisms within a contaminated soil. Lead chromate (PbCrO4), the pigment 'chrome yellow,' is found in paints used to mark highways and occurs along with various organic contaminants in soils where waste paint was discarded. Are the surfaces of lead chromate particles in a contaminated soil as hospitable for the growth of microorganisms as the surfaces of quartz, feldspars, or the aggregates of clay minerals? If not, the microscale distribution of the metal-rich phases may be an important factor in the bioremediation of the organic contaminates in the same soil. This past year we have refined techniques to stain microorganisms in a contaminated soil using a fluorescent dye that will retain its fluorescence even when imbedded in an epoxy resin. Our objective is to prepare thin sections of intact soil, then determine the spatial distribution of the soil microorganisms using fluorescent microscopy and the location of the contaminant metal-rich phases using a combination of light microscopy, electron microprobe analysis, and synchrotron x-ray fluorescence microprobe analysis. Several fluorescent dyes were evaluated. Calcofluor white (CFW) appears to provide the brightest fluorescence, but careful attention to pH during staining is important to assure that the CFW remains in solution. Over the next year we hope to combine all of the steps to locate the microorganisms relative to the contaminating metals.

Impacts
Soils contaminated with both toxic metal and organic compounds are common at sites throughout the U.S. The organic contaminants can often be degraded and removed by microorganisms, but the spatial distribution of the contaminating metals may influence the efficiency of microbial degradation. Thus, understanding the spatial relationships between the contaminant metals and the microorganisms is important for designing effective clean-up strategies.

Publications

  • Schulze, D. G. 2002. An introduction to soil clay mineralogy. In J. B. Dixon and D. G. Schulze (eds.). p. 1-35. In: J. B. Dixon and D. G. Schulze (eds.), Soil Mineralogy with Environmental Applications. Soil Science Society of America, Madison, WI.
  • Huang, P. M., M. K. Wang, N. Kampf, and D. G. Schulze. 2002. Aluminum hydroxides. p. 261-289. In: J. B. Dixon and D. G. Schulze (eds.), Soil Mineralogy with Environmental Applications. Soil Science Society of America, Madison, WI.
  • Bigham, J. M., R. W. Fitzpatrick, and D. G. Schulze. 2002. Iron oxides. p. 323-366. In: J. B. Dixon and D. G. Schulze (eds.), Soil Mineralogy with Environmental Applications. Soil Science Society of America, Madison, WI.


Progress 10/01/00 to 09/30/01

Outputs
Our work this year has utilized micro x-ray diffraction capabilities recently implemented on beamline X26A at the National Synchrotron Light Source, Brookhaven National Laboratory. The equipment on beamline X26A allows us to identify both the elemental composition (from x-ray fluorescence) and the crystalline phases in which those elements reside (from x-ray diffraction) in areas as small as 10 x 10 micrometer (um). By imbedding a sample in an epoxy resin and preparing slices 30 um thick, we are able to obtain detailed information on the spatial distribution of contaminant metal phases in the heterogeneous soil matrix. Microdiffraction is an important compliment to bulk x-ray powder diffraction techniques because bulk diffraction fails to identify important mineral phases when these phases occur at concentrations <5% by weight. As one of the first groups to utilize the new microdiffraction capabilities, we are still developing approaches for analyzing diffraction data that contains both continuous diffraction rings from microcrystalline phases (particles <1 um), plus bright spots due to crystals >1 um. Since the synchrotron beam can be tuned to any incident x-ray wavelength, we also continue to search for the most appropriate standard for x-ray wavelength calibration. Our initial analysis of data from a soil material contaminated with both metals and organics indicates that the Pb and Cr present in the sample occur in the same phase, PbCrO4 (the mineral crocoite), a material sold commercially as "chrome yellow pigment". We had expected that white particles would contain 2PbCO3*Pb(OH)2 (hydrocerussite), or "white lead", which was also used in paint. Our initial analysis, however, indicates that the white material contains TiO2 (rutile; "titanium white") and SiO2 (quartz), both innocuous mineral phases that also occur naturally in soils. Since environmental toxicity is a function of the chemical speciation of an element and not of the absolute amount present, phase identification is crucial to understanding the long-term fate of the Pb and Cr in the contaminated site and for designing appropriate remediation procedures.

Impacts
The environmental toxicity of an element in a soil or contaminated material is due not just to the absolute amount present, but, more importantly, to the chemical form and specific crystalline phase that the element occurs in. For example, metallic chromium in our stainless steel kitchen utensils is nontoxic, but chromium in the form of chromate anions in drinking water is very toxic. The micro x-ray diffraction equipment that we are using at the National Synchrotron Light Source greatly expands our ability to identify the crystalline phase of potentially toxic elements in the complex, heterogeneous material that we call soil. This is important because it provides an additional tool for characterizing contaminated soils prior to deciding how to handle a specific site because potentially toxic elements in one mineral phase may remain nontoxic indefinitely, while the same element in a different mineral phase may be very toxic.

Publications

  • Guest, C. A. 2001. Manganese transformations in soils during waterlogging and subsequent drying. Ph.D. Thesis, Agronomy Department, Purdue University. 115 pp.
  • Azevedo, A. C. 2001. Aggregates and water dispersible clay in Oxisols from southern Brazil. Ph.D. Thesis, Agronomy Department, Purdue University. 104 pp.


Progress 10/01/99 to 09/30/00

Outputs
As we continued to analyze x-ray absorption near edge structure (XANES) data collected during previous sequential extraction studies on 4 surface soils from Indiana, we discovered evidence for the solid state reduction of Mn(IV) to Mn(III). This is the first clear evidence that solid state reduction of Mn occurs in soil Mn oxides and shows that Mn oxides, which are strong oxidants in soils, can take part in soil redox reactions without necessarily releasing Mn to the soil solution. Mn(II) is usually more plant available than the oxidized Mn(III) and Mn(IV) forms. In previous micro-XANES studies of soil Mn oxidation state in the rhizosphere of plant roots, we found areas high in Mn(II) that we could not explain as a result of microbial reduction of Mn(IV) to Mn(II). We collected Mn K XANES spectra from primary mineral grains in the sand fraction and found that considerable Mn occurs in a number of primary soil minerals, and that in many of these minerals the Mn occurs in its reduced, Mn(II) oxidation state. Recognizing this source of Mn(II) will make it easier to interpret high spatial resolution maps of soil Mn oxidation state obtained by XANES spectroscopy. The micrometer scale spatial distribution of trace elements in soils can have an important impact on the bioavailability of both plant essential and potentially toxic trace elements, but techniques for measuring these distributions have not been sensitive enough to study trace elemental distributions at normal soil concentrations. We developed techniques for measuring soil trace element distributions using a synchrotron x-ray fluorescent microprobe, then used these techniques to study the trace element distributions in highly weathered Brazilian Oxisols. The distribution of chemical elements in these soils follows a "hot-spot" pattern where trace elements are highest in: (i) sand-sized primary Al-silicate minerals; (ii) sand-sized primary grains of Ti and Fe oxides; (iii) pieces of old organic matter, including charcoal; (iv) fresh roots and (v) Mn and Fe nodules. The hot spots themselves are randomly distributed within the soil, while elemental distributions within the clayey soil matrix are very homogeneous even at micrometer scales. Work is continuing to extend these techniques to soils contaminated with both metals and organics, particularly with respect to how the distribution of toxic metals impacts bioremediation of the organic pollutants.

Impacts
Manganese is a plant essential trace element whose availability depends greatly on the element's oxidation state. Our work is contributing to a better understanding of how one plant pathogenic fungus, the fungus that causes the take-all disease of wheat, manipulates manganese oxidation state as part of the infection process. Many trace elements are essential elements for plants when they occur in soils at their normal concentrations and in their usual chemical forms, but potentially toxic when they occur in higher concentrations or in certain chemical forms. Some elements, cadmium for example, are considered a potential health threat even at low concentrations. Trace elements can be homogeneously distributed throughout the soil matrix, or concentrated into a few specific minerals in only a few areas of the soil, greatly impacting elemental availability to plants and introduction into the food chain. Our work is providing new information on trace element distributions in soils and how this impacts trace element bioavailability.

Publications

  • Marques, J. J. 2000. Trace element distributions in Brazilian cerrado soils at the landscape and micrometer scales. Ph.D. Thesis, Agronomy Department, Purdue University. 173 pp.
  • Schwertmann, U., J. Friedl, H. Stanjek, and D. G. Schulze. 2000. The effect of Al on Fe oxides. XIX. Formation of Al-substituted hematite from ferrihydrite at 25 degrees C and pH 4 to 7. Clays Clay Miner. 48:159-172
  • Schwertmann, U., J. Friedl, H. Stanjek and D. G. Schulze. 2000. The effect of clay minerals on the formation of iron oxides from ferrihydrite after 16 years of aging at 25 degrees C and pH 4-7. Clays Miner. 35:613-623.
  • Neuhausler, U., C. Jacobson, D. Schulze, D. Stott, and S. Abend. 2000. A specimen chamber for soft x-ray spectromicroscopy on aqueous and liquid samples. J. Synchrotron Rad. 7:110-112.
  • Burrell, L. S., C. T. Johnston, D. Schulze, J. Klein, J. L. White, and S. L. Hem. 2001. Aluminium phosphate adjuvants prepared by precipitation at constant pH. Part I. composition and structure. Vaccine 19:275-281.
  • Burrell, L. S., C. T. Johnston, D. Schulze, J. Klein, J. L. White, and S. L. Hem. 2001. Aluminium phosphate adjuvants prepared by precipitation at constant pH. Part II. Physicochemical properties. Vaccine 19:282-287.
  • Scheinost, A. C., H. Stanjek, D. G. Schulze, U. Gasser, and D. L. Sparks. 2001. Structural environment and oxidation state of Mn in goethite-groutite solid-solutions. Amer. Miner. 86:139-146.


Progress 10/01/98 to 09/30/99

Outputs
We have made steady progress on 3 of our 4 objectives. Objective 1 is to develop synchrotron x-ray techniques to study trace elements in soils and plants. We obtained more experience with our recently designed sample cells that allow us to obtain x-ray absorption spectra around live plant roots at high spatial resolution. We also developed procedures for preparing soil thin sections that allow us to obtain trace element maps at about 10 micrometer spatial resolution using the synchrotron x-ray fluorescence (XRF) microprobe. The mounting materials have no detectable trace element impurities for elements lighter than As when using the XRF microprobe on beamline X26A at the National Synchrotron Light Source. Objective 2 is to determine the role of manganese chemistry in the development of plant fungal diseases. Accomplishments include refinement of a sequential extraction technique that allows us to correlate micro x-ray absorption spectroscopy (XAS) measurements of Mn oxidation state with bulk extraction data. We found that when a saturated, reduced soil was quickly dried (within 4 hours), Mn2+ did not oxidize, and that sequential extraction data and XANES spectra were virtually identical to the same soil prior to drying. We also examined the spatial distribution of Mn and other trace elements in soil that had been microbially reduced. In saturated soil, Mn became redistributed into small (<1 mm), round, dark accumulations and into linear accumulations along fungal hyphae. In addition, we mapped Mn oxidation states in the rhizosphere of a sunflower seedling growing in a sample cell. We did not find the general reduction of Mn in the immediate vicinity of the root that we expected, but we did find a very inhomogeneous pattern of Mn distribution around the root, with some Mn accumulations contained predominately Mn2+, while others contained predominately Mn4+. Objective 4 is to determine trace element concentrations and spatial distributions in agriculturally important Brazilian soils. We prepared soil thin sections (see above) of 5 soils from the Minias Triangle region of Minas Gerais, Brazil, then examined the trace elements at about 10 micrometer spatial resolution using the synchrotron XRF microprobe. Elements analyzed include, K, Ca, Ti, Cr. Mn, Fe, Ni, Cu, Zn, Ga, Ge, As, Pb, Se, and Br. Data collection is still ongoing, but initial indications are that soils weathered from sediments tend to have more homogeneous trace element spatial distributions than soils weathered from basaltic rocks. There is no clear evidence for trace element zoning across soil aggregates in any of the soils. Copper appears to be preferentially concentrated in charcoal particles, apparently because Cu has a higher affinity for organic ligands than other trace elements. Total bulk elemental data is also being collected. Trace elements are important in both plant and animal nutrition. Understanding the distribution and chemical form of trace elements in soils and plants is important in understanding how trace elements move through the food chain, and how deficiencies and toxicities of various trace elements impact plant, animal, and human health.

Impacts
Trace elements are important in both plant and animal nutrition. Understanding the distribution and chemical form of trace elements in soils and plants is important in understanding how trace elements move through the food chain, and in how deficiencies and toxicities of various trace elements impact plant, animal, and human health.

Publications

  • Thompson, I. A., D. G. Schulze, C. A. Guest, and D. M. Huber. 1999. Fungal precipitation of Mn oxides in microbially reduced soil. Abstract 109, Meeting Program and Abstracts, The Clay Minerals Society 36th annual meeting, June 26 - July 1, 1999, Purdue University, West Lafayette, IN.
  • Guest, C., D. Schulze, I. Thompson, A. Scheinost, and D. Huber. 1999. Correlating manganese x-ray absorption near-edge structure (XANES) spectra with extractable soil Mn. Proceedings of Extended Abstracts, 5th International Conference on the Biogeochemistry of Trace Elements, July 11 - 15, 1999, Vienna, Austria, p. 1086-1087.
  • Thompson, I. A., D.M. Huber, D.G. Schulze, and C.A. Guest. 1999. Applications of x-ray absorption near edge structure spectroscopy (XANES) and x-ray fluorescence spectroscopy (XRF) to the study of metals in soils and plant disease interactions. Phytopathology 89:S107.
  • Scheinost, A. C., D. G. Schulze, and U. Schwertmann. 1999. Diffuse reflectance spectra of Al substituted goethite: A ligand field approach. Clays Clay Miner. 47:156-164.
  • Weaver, C. M., D. G. Schulze, L. W. Peck, H. M. Magnusen, B. R. Martin, and S. E. Gruenhagen. 1999. Phosphate-binding capacity of ferrihydrite versus calcium acetate in rats. Am. J. Kidney Diseases 34:324-327.
  • Schulze, D. G. and P. M. Bertsch. 1999. Overview of synchrotron x-ray sources and synchrotron x-rays. p. 1-18. In D. G. Schulze, J. W. Stucki, and P. M. Bertsch (editors). Synchrotron X-ray Methods in Clay Science. The Clay Minerals Society, Boulder, CO.
  • Bertsch, P.M. and D. G. Schulze. 1999. Obtaining access to synchrotron-based techniques. p. 241-244. In D. G. Schulze, J. W. Stucki, and P. M. Bertsch (editors). Synchrotron X-ray Methods in Clay Science. The Clay Minerals Society, Boulder, CO.
  • Kampf, N., A. C. Scheinost, and D. G. Schulze. 1999. Oxide minerals. p. F125 - F168. In: M. E. Sumner (ed.), Handbook of Soil Science. CRC Press, Boca Raton, FL.
  • Schulze, D. G., D. M. Huber, C. A. Guest, I. A. Thompson. 1999. Manganese and associated trace elements at the root-soil interface. Agronomy Abstracts, p. 367.


Progress 10/01/97 to 09/30/98

Outputs
Our work this year has progressed well on 3 of the 4 objectives of this project. Objective 1 is to develop synchrotron x-ray techniques to study trace elements in soils and plants. We have designed, fabricated and tested sample cells that will allow us to do x-ray absorption spectroscopy at the root-soil interface and we are ready to fully test these cells at the synchrotron this fall. We are also developing procedures to prepare self-supporting soil thin sections that will allow us to map trace element distributions at high elemental sensitivity (< 0.1 ppm) and spatial resolution (< 1 micrometer). Objective 2 is to determine the role of manganese chemistry in the development of plant fungal diseases. We have established that X-ray Absorption Near-Edge Structure (XANES) spectroscopy can distinguish between MnII, MnIII, and MnIV oxidation states in mixed systems. Our work has now shifted to correlating sequential chemical extraction of soil Mn with changes in the Mn oxidation state as determined from XANES spectra. NH4-acetate, CuSO4, hydroquinone, and dithionite-citrate-bicarbonate (DCB) were used to sequentially extract increasingly less soluble fractions of Mn from the surface horizons of four soils cropped to wheat. A XANES spectrum of the soil paste was obtained after each step. Using well-aerated soil at field moisture content, the XANES spectra changed little after NH4-acetate and CuSO4 extraction, but after subsequent hydroquinone and DCB extractions the MnIV peak decreased in proportion to Mn removed. After MnIV reduction and removal, the XANES spectra indicated residual MnII and MnIII, apparently within the crystal structures of aluminosilicate minerals. Using microbially reduced soil that had been saturated for 7 days, NH4-acetate extracted 37 percent and CuSO4 an additional 25 percent of the total reductant-extractable Mn. A progressive reduction in the intensity of the MnII peak indicated that both extractants were removing MnII that had been solubilized by microbial activity. The MnII remaining after the NH4-acetate extraction, but removed by CuSO4, may be a sizable pool of MnII sequestered by microorganisms. We plan to use this new information to map the distribution of plant-available manganese in the soil around live plant roots. This will allow us to determine whether fungi that cause soil-borne diseases like the take all disease of wheat do, in fact, manipulate soil manganese chemistry as part of the disease process. This could lead to more effective control of this major plant disease. Objective 4 is to determine trace element concentrations and spatial distributions in agriculturally important Brazilian soils. Field sampling of 45 soils from the cerrado region was finished in March in collaboration with Brazilian scientists. We plan to study trace element distributions in these soils after the thin section technique mentioned above has been fully developed. This work will provide an important link between bulk chemical extraction methods usually used in the laboratory to study trace element availability, and the plant-essential trace elements that plant roots encounter as they grow through soil.

Impacts
(N/A)

Publications

  • No publications reported this period


Progress 10/01/96 to 09/30/97

Outputs
Manganese appears to play an important role in determining the severity of plant fungal diseases such as the take-all disease of wheat and the blast disease of rice. For both diseases, we have previously found that Mn is present in its physiologically unavailable Mn4+ form at the infection site, suggesting that fungal oxidation of Mn from its physiologically active Mn2+ form in necrotic diseases is an important step in the disease process. Phytophthora sojae causes a wilt type of disease and is a major soybean pathogen in Indiana. We used micro-X-ray absorption near edge structure (XANES) spectroscopy to measure Mn oxidation state in dried hypocotyl tissue of soybean seedlings inoculated with P. sojae. We found little or no oxidation of Mn in the inoculated tissue as compared to undamaged control tissue and wounded control tissue. Total Mn, however, was higher in inoculated tissue than in undamaged and wounded control tissue regardless of the disease reaction. This suggests that the plant is mobilizing Mn to the infection site in response to invasion by P. sojae. P. sojae does not, however, appear to oxidize Mn during development of this wilt type disease.

Impacts
(N/A)

Publications

  • T. L. Rinehart, D. G. Schulze, R. M. Bricka, S. Bajt, and E. R. Blatchley, III. 1997. Chromium leaching versus oxidation state for a contaminated solidified/stabilized soil. J. Haz. Mat. 52:213-221.
  • Gruenhagen, S. E., D. G. Schulze, G. Chansiri, K. J. Hem, J. L. White, and S. L. Hem. 1997. Effect of sorbitol on the phosphate adsorptive capacity of ferrihydrite suspensions. Phar. Dev. Tech. 2:81-86.
  • Schulze, D. G., and D. E. Stott. 1997. Soil structure alteration: The role of soil mineralogy, chemistry, and microbiology. Proceedings of the XXVI Congress of the Brazilian Society of Soil Science, Rio de Janiero, Brazil, 20-26 July 1997.


Progress 10/01/95 to 09/30/96

Outputs
The blast disease is one of the most important plant diseases worldwide because rice is a major source of food for 60% of the world's population. Manganese is an essential mineral element for photosynthesis, lignin synthesis, and other plant metabolic functions in its Mn2+ or Mn3+ forms, but when oxidized to Mn4+ it precipitates as physiologically unavailable Mn oxides and hydroxides. Pyricularia grisea (Cooke) Sacc., the fungal causative agent of rice blast, is a strong Mn oxidizer in agar culture. Thus, fungal oxidation of Mn may be an important part of the disease processes. We used micro x-ray absorption near edge structure (XANES) spectroscopy to compare Mn oxidation states in healthy areas of rice leaves with Mn oxidation states in blast lesions caused by P. grisea. Healthy tissue contained only Mn2+, whereas blast lesions contained significant quantities of Mn4+. We examined 6 isogenic rice cultivars which differed in their resistance to 12 races of the fungal pathogen. Mn4+ was always detected in fungal lesions which were as large or larger than the incident x-ray beam (about 150 x 200 micrometers). The presence of Mn4+ in smaller lesions cannot be ruled out at this time. Mn4+ was not detected in mechanically wounded tissue, thus Mn oxidation is not the result of mechanical disruption of the plant cell by the fungus. The ability to oxidize Mn may be a significant factor determining the virulence of P. grisea.

Impacts
(N/A)

Publications

  • Schulze, D. G. 1996. Teaching soil mineralogy. Proceedings of the XXV Congresso Brasileiro de Cincia do Solo (25th Congress of the Brazilian Soil Science Society). 23-29 July, 1995, Universidade Federal de Viosa, Viosa, Minas Gerais, Bra de Brito
  • Galvo, T. C. and D. G. Schulze. Mineralogical properties of a collapsible lateritic soil from Minas Gerais, Brazil. Soil Sci. Soc. Amer. J. (in press).


Progress 10/01/94 to 09/30/95

Outputs
Our work this year has focused on the role of manganese oxidation-reduction reactions in the blast disease of rice, a fungal disease which attacks rice leaves. The blast disease is one of the most important plant diseases worldwide because rice is a major source of food for 60% of the world's population. Manganese is an essential mineral element for photosynthesis, lignin synthesis, and other plant metabolic functions in its Mn2+ or Mn3+ forms, but when oxidized to Mn4+ it precipitates as physiologically unavailable Mn oxides and hydroxides. Pyricularia grisea (Cooke) Sacc., the fungal causative agent of rice blast, is a strong Mn oxidizer in agar culture. Thus, fungal oxidation of Mn may be an important part of the disease processes. We used micro x-ray absorption near edge structure (XANES) spectroscopy to compare Mn oxidation states in healthy areas of rice leaves with Mn oxidation states in blast lesions caused by P. grisea. Healthy tissue contained only Mn2+, whereas blast lesions contained significant quantities of Mn4+. These results suggest that the ability to oxidize Mn may be a significant factor in determining the virulence of P. grisea and that resistant rice varieties may have developed strategies to suppress or prevent Mn oxidation by the fungus. We have also continued work to develop procedures to use micro-XANES spectroscopy to study Mn oxidation state around wheat roots infected with G. graminis, the soil-borne fungus which causes the take-all disease.

Impacts
(N/A)

Publications


    Progress 10/01/93 to 09/30/94

    Outputs
    Take-all disease, a root and foot rot of wheat caused by the fungus Gaeumannomyces graminis var. tritici (Ggt), considerably reduces wheat yields in many parts of the world. Ggt is known to oxidize Mn in culture media and there is considerable evidence from field and growth chamber studies that the severity of take-all is related to the Mn nutrition of the plant. We are testing the hypothesis that Ggt oxidizes soluble Mn(superscript 2+) to insoluble Mn(superscript 4+) in the soil around wheat roots, thus inducing a Mn deficiency which weakens the plant and allows infection to occur. We are using micro-x-ray absorption near edge structure (XANES) spectroscopy on beam line X26A at the National Synchrotron Light Source at Brookhaven National Laboratory to study the oxidation state of Mn near fresh wheat roots grown in agar and in soil. This past year we used XANES spectra from mixtures of MnSO(subscript 4)-H(subscript 2)O (Mn(superscript 2+)) and a synthetic Na-birnessite (Mn(superscript 4+)) to develop a calibration curve for determining the fraction of total Mn present as Mn(superscript 2+). Using this function, we were able to obtain calibrated maps of Mn oxidation state around wheat roots growing in agar amended with Mn(superscript 2+) and infested with Ggt. We also showed that of the total Mn in 4 air-dried, Indiana soils infested with Ggt, about 70% was present as Mn(superscript 4+) and 30% was present as Mn(superscript 2+).

    Impacts
    (N/A)

    Publications


      Progress 10/01/92 to 09/30/93

      Outputs
      Take-all disease, a root and foot rot of wheat caused by the fungus Gaeumannomyces graminis var. tritici (Ggt), considerably reduces wheat yields in many parts of the world. Ggt is known to oxidize Mn in culture media and there is considerable evidence from field and growth chamber studies that the severity of take-all is related to the Mn nutrition of the plant. We are testing the hypothesis that Ggt oxidizes Mn in the soil around wheat roots, thus inducing a Mn deficiency which weakens the plant and allows infection to occur. We are using micro-x-ray absorption near edge structure (XANES) spectroscopy on beam line X26A at the National Synchrotron Light Source at Brookhaven National Laboratory to study the oxidation state of Mn near fresh wheat roots grown in agar and in soil. An absorption edge near 6545 eV indicates Mn(superscript 2+), while a shift to 6549 eV indicates Mn(superscript 2+). We have obtained some of the first ever oxidation state maps using the XANES technique. A map of a Ggt infected wheat root showed an accumulation of Mn(superscript 4+) in the interior of the root and Mn(superscript 2+) in the surrounding agar. We have recently obtained spectra of standards containing varying Mn(superscript 2+):Mn(superscript 4+) ratios and are analyzing this data to prepare standard curves for determining oxidation state in unknown samples. We have also obtained usable Mn XANES spectra from soils.

      Impacts
      (N/A)

      Publications


        Progress 10/01/91 to 09/30/92

        Outputs
        Take-all disease, a root and foot rot of wheat caused by the fungus Gaeumannomyces graminis var. tritici (Ggt), considerably reduces wheat yields in many parts of the world. Ggt oxidizes Mn in culture media and there is evidence from field and growth chamber studies that the severity f take-all is related to the Mn nutrition of the plant. We used micro-x-ray absorption near edge structure (XANES) spectroscopy on beam line X26A at the National Synchrotron Light Source at Brookhaven National Laboratory to study the oxidation state of Mn near fresh wheat roots grown in agar. Black areas of roots infected with Ggt were compared to clear agar and to uninfected areas of the same root. Mn in clear agar, or in uninfected roots growing in Mn-amended agar but with no apparent Ggt infection, occurred predominately as Mn2+ as indicated by absorption edges near 6545 eV. Count rates indicated little or no net accumulation of Mn2+ by the roots. Absorption edges near 6549 eV and count rates 10 to 20 times greater than the clear agar confirmed the accumulation of Mn4+ oxides around the infected root. The results indicate that Ggt can oxidize Mn2+ to Mn4+ in the rhizosphere of wheat seedlings grown in agar, but the current data are insufficient to prove that this is part of the infection process. These initial experiments demonstrate that micro-XANES and other synchrotron-based techniques have considerable potential for unraveling the chemistry and mineralogy of Mn and other metals in the rhizosphere.

        Impacts
        (N/A)

        Publications


          Progress 10/01/90 to 09/30/91

          Outputs
          A patent has been issued for our real-time soil organic matter sensor and an agricultural equipment manufacturer has developed a unit for limited commercial distribution. A fertility experiment is underway to test whether managing soils differently within a field based on soil type has significant advantages in central Indiana. The field has two distinct soil types and the experiment has 3 levels of N fertilizer, 2 hybrids, and 3 levels of plant population per hybrid. The first year of data has not yet been analyzed. The particle size distribution and trace element chemistry of rural atmospheric aerosols is important in regional toxicity assessment. We selected aerosol samples collected near Vincinnes, Indiana that were representative of air masses arriving from the western Great Plains, the Gulf of Mexico, and the Atlantic coast, and of air masses stagnant over the Midwest. We used the x-ray fluorescence microprobe on beamline X26 at the National Synchrotron Light Source to determine the trace element chemistry of the 3.3 - 7 micrometer size fraction. Initial analysis suggests that air arriving from the Great Plains had an order of magnitude less Cu and Zn than air from the other areas. This suggests that the "background" composition of rural aerosols can vary depending on the source region of the arriving air, and that there differences must be understood when studying aerosol dispersion from specific point sources.

          Impacts
          (N/A)

          Publications


            Progress 10/01/89 to 10/30/90

            Outputs
            Our efforts to develop a real-time soil organic matter sensor have entered a newphase. The technology has been licensed to an agricultural equipment manufacturer and we are interacting with the company as needed as they further develop the technology. Ferrihydrite, a poorly crystallized iron oxide mineral, is a potential phosphate binder for kidney dialysis patients with few side affects than current P binders. Cooperative studies with a pharmaceutical manufacturer have been encouraging. Ferrihydrite is a strong phosphate fixer in soil systems as well, and the pharmaceutical work should provide valuable insights into the role of this mineral in plant nutrition. The extremely bright x-rays produced by synchrotrons have a wide variety of potential applications in the soil and agricultural sciences. In an preliminary experiment, we obtained trace element composition of atmospheric aerosols from southern Indiana using the x-ray fluorescence microprobe at the National Synchroton Light Source at Brookhaven National Laboratory. We detected Cu, Zn, Cr, Ni, Mn, Ti, Zn, and Sr in dust particles from an air mass that had been over the High Plains of the U.S. 24 hours earlier. This is the only way to fully analyze such small, dilute samples. We plan to use trace element composition of aerosol particles to determine if abandoned mine and industrial sites pose significant health hazards to rural Indiana residents.

            Impacts
            (N/A)

            Publications


              Progress 10/01/88 to 09/30/89

              Outputs
              The changing pattern of light and dark soils observed in the glaciated Midwestern U.S. is caused by differences in soil organic matter content and iron oxide mineralogy. Soil organic matter content, & associated soil color, can vary spatially with soil type within individual fields. Some pesticides are deactivated by soil organic matter and recommended application rates vary greatly depending on organic matter content. We have continued testing a prototype soil organic matter sensor on a variety of soil landscapes in Indiana and Illinois. Soil samples collected during each field test are being analyzed for organic matter, color, texture, pH, and nutrient status. Preliminary results suggest that the relationship between organic matter content and color for silt loam and silty clay loam soils is the same for both Illinois soils formed under prairie and Indiana soils formed under forest vegetation. Color-organic matter relationships may not be as variable from place to place as originally believed. Soil texture, however, plays a major role in color-organic matter relationships, and its influence requires more study. Extremely variable crop growth on the sandy soils of Niger, West Africa, was shown to be related to phosphorous content in the soil solution. Unproductive areas where plants die during the growing season supply almost no P to the soil solution, while productive areas do.

              Impacts
              (N/A)

              Publications


                Progress 10/01/87 to 09/30/88

                Outputs
                The changing pattern of light and dark soils observed in the glaciated Midwestern U.S. is caused by differences in soil organic matter content and iron oxide mineralogy. Soil organic matter content, and associated soil color, can vary spatially with soil type within individual fields. Some pesticides are deactivated by soil organic matter and recommended application rates for these materials vary greatly depending on soil organic matter content. We have tested a prototype soil organic matter sensor which is designed to be attached to agricultural equipment. Tests on 5 fields varying in size from about 1 to 7 hectares have shown that the sensor can accurately track soil color under field conditions. A sensor such as this has the potential to vary pesticide application rates as equipment moves across the field, thus reducing potential groundwater contamination cause by over-application of such chemicals. Iron oxide minerals color soils brown and red. The presence or absence of particular minerals and the properties of the minerals themselves may provide information on how soils formed. We have studied the substitution of Mn in the structure of goethite under laboratory conditions. We were able to synthesize pure goethite with up to 0.47 mole fraction Mn. This mineral may occur in some soil concretions and may also have applications as an industrial catalyst.

                Impacts
                (N/A)

                Publications


                  Progress 10/01/86 to 09/30/87

                  Outputs
                  Color is one of the most obvious of soil properties. Brown or red iron oxide minerals and black or dark-brown organic matter are the main pigments which color soils. The relationships between the kinds and amounts of these various pigments and soil colors are poorly understood. Our previous work has centered on developing laboratory techniques to accurately measure soil color. During the past year, these techniques were used to study soil color - organic matter relationships within eight Indiana soil landscapes. For each landscape, eight to twelve surface soil samples were collected to represent the range of colors in the field. Color, organic matter content, and adsorption of the pesticide diuron were determined on each sample. Munsell value, a measure of how dark the soil is, was found to be closely correlated with organic matter content. The correlation between color and organic matter content within a landscape is much better than correlations developed over a wider geographic area. Diuron adsorption was closely correlated with both organic matter content and soil color. The close correlation between color and organic matter content within soils closely associated within the same landscape will form the theoretical basis for a soil color sensor which will be able to sense soil color in the field and then adjust herbicide or fertilizer rate in response to soil type as the equipment moves across a field. A prototype sensor has been developed in cooperation with agricultural engineers and testing is in progress.

                  Impacts
                  (N/A)

                  Publications


                    Progress 10/01/85 to 09/30/86

                    Outputs
                    Brown or red iron oxide minerals and black or dark-brown organic matter are the main pigments which color soils. The relationships between the kinds and amounts of these various pigments and soil colors are poorly understood. We use the CARY 17D UV-VIS spectrophotometer to obtain reflectance spectra of soils and of mixtures of clay and iron oxide minerals. Computer programs are used to convert the spectral data to the CIE and Munsell color notations. We are currently attempting to apply Kubelka-Munk analysis to predict the colors of mixtures of kaolinite and synthetic goethites and hematites. The result of Kubelka-Munk analysis is a set of scattering and absorption coefficients which describe the pigmenting properties of a given pigment. These coefficients can then be used to predict the colors of any desired mixture of pigments, reducing the need to make large numbers of physical mixtures of scarce pigments. In addition to the color work, synthesis experiments have shown that: (1) goethites crystallized at 25 degrees C have more structural defects than goethites crystallized at 70 degrees C, and (2) the presence of Mn suppresses the formation of goethite in favor of hematite and a poorly crystalline, strongly magnetic, mixed Fe-Mn oxide.

                    Impacts
                    (N/A)

                    Publications


                      Progress 01/01/85 to 12/30/85

                      Outputs
                      Iron oxide minerals are the brown and red pigmenting materials in soils. The relationships between the kinds and amounts of Fe oxide minerals and soil colors are, however, poorly understood. We have made progress in developing procedures to quantify soil color accurately in the laboratory. We are using a CARY 17D UV-VIS spectrophotometer to obtain reflectance spectra of soils in the visible region. These spectra are then processed by a computer program which calculates the color notation in the CIE system. The CIE notation is then converted to the Munsell notation familiar to soil scientists. This past year we have completed the testing of our computer programs and measurement procedures. We have measured the spectra of the Munsell soil color chips both as a test of our procedures and as a reference for comparison with soil spectra. We have also completed color measurements on a transect of well-drained soils collected along the Mississippi River from Minnesota in the north to Mississippi in the south. The soils are all believed to have formed from loess deposited during the last ice age. Our data indicate that there is an overall reddening in the color of the Bt horizons from north to south, indicating that hematite is forming as a weathering product in the south, but not in the north. Data analysis is still incomplete, but we hope to be able to identify the soil climate properties most likely to promote the formation of hematite.

                      Impacts
                      (N/A)

                      Publications


                        Progress 01/01/84 to 12/30/84

                        Outputs
                        Iron oxide minerals are the brown and red pigmenting materials in soils. However, the relationships between the kinds and amounts of Fe oxide minerals and soil colors are poorly understood. We have made progress in developing procedures to quantify soil color accurately in the laboratory. We are using a CARY 17D UV-VIS spectrophotometer to obtain reflectance spectra of soils in the visible region. These spectra are then processed by a computer program which calculates the color notation in the CIE system. The CIE notation is then converted to the Munsell notation familiar to soil scientists. The past year we have been working primarily on procedural problems such as sample and standard preparation and computer programs to process the data. A program was obtained to make the CIE to Munsell conversion. Some color data have been obtained on A and B horizons of a toposequence of soils sampled on the Wisconsin Till plane near Lafayette, IN. Although the B+ horizons all have 10YR hues as determined from the Munsell soil color charts, the more percise instrumental measurements indicate that the better drained soils have B+ horizons with hues slightly redder than 10YR. This could indicate either: (a) differences in the relative amounts of iron oxide minerals present, or (b) differences in the crystal size, shape, or structural defect caused by the differences in the soil moisture regime.

                        Impacts
                        (N/A)

                        Publications


                          Progress 01/01/83 to 12/30/83

                          Outputs
                          Iron oxide minerals are the brown and red pigmenting materials in soils. An improved computer program was written to obtain differential x-ray diffraction (DXRD) patterns of iron oxide minerals in soil clays. The DXRD pattern is used for mineral identification and, if possible, quantification. Data are being collected to correlate iron oxide mineralogy (from DXRD) with the color of the sample.

                          Impacts
                          (N/A)

                          Publications