I grew up in Clintonville, Wisconsin and obtained B.A. degrees in geography and German from the University of Wisconsin, Madison, an M.A. degree in geography from the University of California, Davis, and a PhD in soil science, also from UC-Davis. Then came an 8-year post-doctoral research position at the International Rice Research Institute, in the Philippines. Starting at NLAE in 2001 as a soil biochemist, my group (Terry Grimard and visiting scientists) has investigated the roles of individual carbohydrates, phenols, amino acids, and fatty acids in cropping sustainability and soil carbon sequestration under field management treatments for corn, soybean, and rice. Together with Dana Dinnes, we also measure and seek to explain the field efficacy of humic products for increasing crop growth and improving soil properties. More recently, we are examining management options for degrading hardened subsoil fragipans in the Eastern U.S. Hobbies include aerobic sports, genealogy, and international travel.

• Publications

  • (Clicking on the reprint icon will take you to the publication reprint.)
  • Mineral changes in the rhizospheres of conifer plantations for a weathered subtropical soil -(Peer Reviewed Journal)
    Hummes, A.P., Inda, A.V., Olk, D.C., Bortoluzzi, E.C. 2024. Mineral changes in the rhizospheres of conifer plantations for a weathered subtropical soil. Soil Science Society of America Journal. https://doi.org/10.1002/saj2.20682.
    
  • Constraints on mineral-associated and particulate organic carbon response to regenerative management: carbon inputs and saturation deficit -(Peer Reviewed Journal)
    King, A.E., Amsili, J.P., Córdova, S.C., Culman, S., Fonte, S.J., Kotcon, J., Masters, M.D., McVay, K., Olk, D.C., Prairie, A.M., Schipanski, M., Schneider, S.K., Stewart, C.E., Cotrufo, M. 2024. Constraints on mineral-associated and particulate organic carbon response to regenerative management: carbon inputs and saturation deficit. Soil & Tillage Research. 238. https://doi.org/10.1016/j.still.2024.106008.
    
  • Miscanthus increases soil amino compounds regardless of nitrogen fertilizer rate-(Abstract Only)
    Khaleel, A., Thompson, M.L., Olk, D.C., Mcdaniel, M.D. 2023. Miscanthus increases soil amino compounds regardless of nitrogen fertilizer rate [abstract]. ASA-CSSA-SSSA Annual Meeting. Paper No. 154264.
    
  • Interactive effects of humic product application with nitrogen fertilizer rates on corn grain yield in a central Iowa field study-(Abstract Only)
    Olk, D.C., Dinnes, D.L. 2023. Interactive effects of humic product application with nitrogen fertilizer rates on corn grain yield in a central Iowa field study [abstract]. ASA-CSSA-SSSA Annual Meeting. Paper No. 252-4.
    
  • A soil matrix capacity index to predict mineral-associated but not particulate organic carbon across a range of climate and soil pH -(Peer Reviewed Journal)
    King, A.E., Amsili, J.P., Cordova, S., Culman, S., Fonte, S.J., Kotcon, J., Liebig, M.A., Masters, M.D., Mcvay, K., Olk, D.C., Schipanski, M., Schneider, S.K., Stewart, C.E., Cotrufo, M. 2023. A soil matrix capacity index to predict mineral-associated but not particulate organic carbon across a range of climate and soil pH. Biogeochemistry. 165:1-14. https://doi.org/10.1007/s10533-023-01066-3.
    
  • Molecular composition and possible transformations of labile soil organic matter fractions in Mediterranean arable soils: Relevance and implications -(Peer Reviewed Journal)
    Abdelrahman, H., Hofmann, D., Sleighter, R.L., Olk, D.C., Berns, A.E., Miano, T.M., Shaheen, S.M., Cocozza, C. 2023. Molecular composition and possible transformations of labile soil organic matter fractions in Mediterranean arable soils: Relevance and implications. Environmental Research. 232. https://doi.org/10.1016/j.envres.2023.116315.
    
  • Variable humic product effects on maize structural biochemistry across annual weather patterns and soil types in two Iowa (U.S.A.) production fields -(Peer Reviewed Journal)
    Olk, D.C., Dinnes, D.L., Hatfield, R.D., Scoresby, J.R., Darlington, J.W. 2023. Variable humic product effects on maize structural biochemistry across annual weather patterns and soil types in two Iowa (U.S.A.) production fields. Frontiers in Plant Science. 13. https://doi.org/10.3389/fpls.2022.1058141.
    
  • Stimulation of corn root growth by humic products in Iowa fields: implications for soil properties-(Abstract Only)
    Olk, D.C., Dinnes, D.L. 2022. Stimulation of corn root growth by humic products in Iowa fields: implications for soil properties [abstract]. ASA-CSSA-SSSA Annual Meeting. Paper No. 147-5.
    
  • Moderator of panel discussion: Is it important for agronomists to publish in high-profile journals?-(Abstract Only)
    Olk, D.C. 2022. Moderator of panel discussion: Is it important for agronomists to publish in high-profile journals? [abstract]. ASA-CSSA-SSSA Annual Meeting. Paper No. 58-6.
    
  • Introduction of aerobic soil conditions alter yield potential in California rice-(Abstract Only)
    Zhenglin, Z., Olk, D.C., Linquist, B.A. 2022. Introduction of aerobic soil conditions alter yield potential in California rice [abstract]. ASA-CSSA-SSSA Annual Meeting. Paper No. 81-5.
    
  • Formation efficiency of soil organic matter from plant litter is governed by clay mineral type more than plant litter quality -(Peer Reviewed Journal)
    Yuzhi, X., Liu, K., Yao, S., Zhang, Y., Zhang, X., He, H., Feng, W., Ndzana, G.M., Chenu, C., Olk, D.C., Mao, J., Bin, Z. 2022. Formation efficiency of soil organic matter from plant litter is governed by clay mineral type more than plant litter quality. Geoderma. 412. Article e115727. https://doi.org/10.1016/j.geoderma.2022.115727.
    
  • Maize growth responses to a humic product in Iowa production fields: An extensive approach -(Peer Reviewed Journal)
    Olk, D.C., Dinnes, D.L., Callaway, C.R. 2022. Maize growth responses to a humic product in Iowa production fields: An extensive approach. Frontiers in Plant Science. 12. Article e778603. https://doi.org/10.3389/fpls.2021.778603.
    
  • Tree species of wet tropical forests differ in their tissue biochemistry and effects on soil carbon dynamics -(Database / Dataset)
    Russell, A.E., Marek, R.F., Olk, D.C. 2021. Tree species of wet tropical forests differ in their tissue biochemistry and effects on soil carbon dynamics. Dryad Digital Repository. https://doi.org/10.5061/dryad.fbg79cntt.
    
  • Maize growth and grain yield responses to a micronized humic product across soil types and annual weather patterns in Central Iowa, United States -(Peer Reviewed Journal)
    Olk, D.C., Dinnes, D.L., Scoresby, R.J., Darlington, G.W., Hurburgh, C.R., Rippke, G.R. 2021. Maize growth and grain yield responses to a micronized humic product across soil types and annual weather patterns in Central Iowa, United States. Frontiers in Plant Science. 12. Article 672078. https://doi.org/10.3389/fpls.2021.672078.
    
  • Tree species of wet tropical forests differ in their tissue biochemistry and effects on soil carbon dynamics -(Peer Reviewed Journal)
    Russell, A.E., Marek, R.F., Olk, D.C. 2021. Tree species of wet tropical forests differ in their tissue biochemistry and effects on soil carbon dynamics. Frontiers in Forests and Global Change. 4. Article 674213. https://doi.org/10.3389/ffgc.2021.674213.
    
  • Soil texture and straw type modulate the chemical structure of residues during four-year decomposition by regulating bacterial and fungal communities -(Peer Reviewed Journal)
    Li, D., Zhao, B., Olk, D.C., Zhang, J. 2020. Soil texture and straw type modulate the chemical structure of residues during four-year decomposition by regulating bacterial and fungal communities. Applied Soil Ecology. 155. Article 103664. https://doi.org/10.1016/j.apsoil.2020.103664.
    
  • Formation of char-like, fused-ring aromatic structures from a nonpyrogenic pathway during decomposition of wheat straw -(Peer Reviewed Journal)
    Chen, X., Ye, X., Chu, W., Olk, D.C., Cao, X., Schmidt-Rohr, K., Zhang, L., Thompson, M.L., Mao, J., Gao, H. 2020. Formation of char-like, fused-ring aromatic structures from a nonpyrogenic pathway during decomposition of wheat straw. Journal of Agricultural and Food Chemistry. 68(9):2607-2614. https://doi.org/10.1021/acs.jafc.9b06037.
    
  • Changes in labile fractions of soil organic matter during the conversion to organic farming -(Peer Reviewed Journal)
    Abdelrahman, H.M., Cocozza, C.C., Olk, D.C., Ventrella, D., Montemurro, F., Miano, T. 2020. Changes in labile fractions of soil organic matter during the conversion to organic farming. Journal of Soil Science and Plant Nutrition. https://doi.org/10.1007/s42729-020-00189-y.
    
  • Whole-profile soil organic matter content, composition, and stability under cropping systems that differ in belowground inputs -(Peer Reviewed Journal)
    Poffenbarger, H.J., Olk, D.C., Cambardella, C.A., Kersey, J., Liebmann, M., Mallarino, A., Six, J., Castellano, M.J. 2020. Whole-profile soil organic matter content, composition, and stability under cropping systems that differ in belowground inputs. Agriculture, Ecosystems and Environment. 291. https://doi.org/10.1016/j.agee.2019.106810.
    
  • Carbohydrate and amino acid profiles of cotton plant biomass products -(Peer Reviewed Journal)
    He, Z., Olk, D.C., Tewolde, H., Zhang, H., Shankle, M. 2019. Carbohydrate and amino acid profiles of cotton plant biomass products. Agriculture. 10(1):2. https://doi.org/10.3390/agriculture10010002.
    
  • Long-Term benefits of humic product application to soil organic matter and physical properties in Iowa corn-soybean rotations-(Abstract Only)
    Olk, D.C., Dinnes, D.L., Abdelrahman, H.M., Scoresby, R.J. 2019. Long-Term benefits of humic product application to soil organic matter and physical properties in Iowa corn-soybean rotations. In proceedings of ASA-SSSA-CSA Annual Meeting, Nov 10-13,2019, San Antonio, Texas. Available: https://scisoc.confex.com/scisoc/2019am/meetingapp.cgi/Paper/120820.
    
  • Potential alterations in the chemical structure of soil organic matter components during sodium hydroxide extraction -(Peer Reviewed Journal)
    Chen, X., Jin, M., Xu, Y., Chu, W., Olk, D.C., Hu, J., Jiang, Y., Mao, J., Gao, H., Thompson, M.L. 2019. Potential alterations in the chemical composition of soil organic matter during NaOH extraction. Journal of Environmental Quality. 48(6):1578-1586. https://doi.org/10.2134/jeq2019.02.0077.
    
  • Demonstration of chemical distinction among soil humic fractions using quantitative solid-state 13C NMR -(Peer Reviewed Journal)
    Xu, J., Zhao, B., Li, Z., Chu, W., Mao, J., Olk, D.C., Zhang, J., Xin, X., Wei, W. 2019. Demonstration of chemical distinction among soil humic fractions using quantitative solid-state 13C NMR. Journal of Agricultural and Food Chemistry. 67(29):8107-8118. https://doi.org/10.1021/acs.jafc.9b02269.
    
  • Application of a formulated humic product can increase soybean yield -(Peer Reviewed Journal)
    Lenssen, A.W., Olk, D.C., Dinnes, D.L. 2019. Application of a formulated humic product can increase soybean yield. Crop, Forage & Turfgrass Management. 5(1):1-6. https://doi.org/10.2134/cftm2018.07.0053.
    
  • Developments in agricultural soil quality and health: Reflections by the Research Committee on soil organic matter management -(Peer Reviewed Journal)
    Wander, M.M., Cihacek, L.J., Coyne, M., Drijber, R.A., Grossman, J.M., Gutknecht, J.L., Horwath, W.R., Jagadamma, S., Olk, D.C., Ruark, M., Snapp, S.S., Tiemann, L.K., Weil, R., Turco, R.F. 2019. Developments in agricultural soil quality and health: Reflections by the Research Committee on soil organic matter management. Frontiers in Environmental Science. https://doi.org/10.3389/fenvs.2019.00109.
    
  • Using humic fractions to understand natural organic matter processes in soil and water: Selected studies and applications -(Peer Reviewed Journal)
    Olk, D.C., Bloom, P.R., De Nobili, M., Chen, Y., McKnight, D.M., Wells, M.J.M., Weber, J. 2019. Using humic fractions to understand natural organic matter processes in soil and water: Selected studies and applications. Journal of Environmental Quality. 48(6):1633-1643. https://doi.org/10.2134/jeq2019.03.0100.
    
  • Can humic products substantially improve ecosystem quality and economic yield?-(Peer Reviewed Journal)
    Olk, D.C., Dinnes, D.L., Scoresby, J.R., Callaway, C.R., Darlington, J.W. 2019. Can humic products substantially improve ecosystem quality and economic yield? Silva Balcanica. 20(1):95-110.
    
  • Nitrogen fertilizer suppresses mineralization of soil organic matter in maize agroecosystems -(Peer Reviewed Journal)
    Mahal, N.K., Osterholz, W.R., Miguez, F.E., Poffenbarger, H.J., Sawyer, J.E., Olk, D.C., Archontoulis, S.V., Castellano, M.J. 2019. Nitrogen fertilizer suppresses mineralization of soil organic matter in maize agroecosystems. Frontiers in Ecology and Evolution. https://doi.org/10.3389/fevo.2019.00059.
    
  • Environmental and agricultural relevance of humic fractions extracted by alkali from soils and natural waters -(Peer Reviewed Journal)
    Olk, D.C., Bloom, P.R., Perdue, E.M., McKnight, D.M., Chen, Y., Farenhorst, A., Senesi, N., Chin, Y.P., Schmitt-Kopplin, P., Hertkorn, N., Harir, M. 2019. Environmental and agricultural relevance of humic fractions extracted by alkali from soils and natural waters. Journal of Environmental Quality. 48:217-232. https://doi.org/10.2134/jeq2019.02.0041.
    
  • Chemical nature of soil organic carbon under different long-term fertilization regimes is coupled with changes in the bacterial community in a Calcaric Fluvisol -(Peer Reviewed Journal)
    Li, D., Chen, L., Xu, J., Ma, L., Olk, D.C., Zhao, B., Zhang, J., Xin, X. 2018. Chemical nature of soil organic carbon under different long-term fertilization regimes is coupled with changes in the bacterial community in a Calcaric Fluvisol. Biology and Fertility of Soils. 54:999-1012. https://doi.org/10.1007/s00374-018-1319-0.
    
  • Legacy effects of long-term nitrogen fertilizer application on the fate of nitrogen fertilizer inputs in continuous maize -(Peer Reviewed Journal)
    Poffenbarger, H.J., Sawyer, J.E., Barker, D., Olk, D.C., Six, J., Castellano, M.J. 2018. Legacy effects of long-term nitrogen fertilizer application on the fate of nitrogen fertilizer inputs in continuous maize. Agriculture Ecosystems and the Environment. 265:544-555. https://doi.org/10.1016/j.agee.2018.07.005.
    
  • Plant litter quality affects the accumulation rate, composition, and stability of mineral-associated soil organic matter -(Peer Reviewed Journal)
    Cordova, S.C., Olk, D.C., Dietzel, R., Mueller, K., Archontouilis, S., Castellano, M. 2018. Plant litter quality affects the accumulation rate, composition, and stability of mineral-associated soil organic matter. Soil Biology and Biochemistry. 125:115-124. https://doi.org/10.1016/j.soilbio.2018.07.010.
    
  • Distinct changes in composition of soil organic matter with length of cropping time in subsoils of a Phaeozem and Chernozem -(Peer Reviewed Journal)
    Zhang, Y., Li, L., Mao, J., Yao, S., Schmidt-Rohr, K., Olk, D.C., Cao, X., Cui, J., Zhang, B. 2018. Distinct changes in composition of soil organic matter with length of cropping time in subsoils of a Phaeozem and Chernozem. European Journal of Soil Science. https://onlinelibrary.wiley.com/doi/pdf/10.1111/ejss.12688.
    
  • Amino acid and carbohydrate profiles of cotton plant biomass products-(Proceedings)
    He, Z. 2018. Amino acid and carbohydrate profiles of cotton plant biomass products. In: Proceedings of the 2018 Beltwide Cotton Conferences, January 3-5, 2018, San Antonio, Texas. p. 115-119.
    
  • Contributions of residue-C and -N to plant growth and soil organic matter pools under planted and unplanted conditions -(Peer Reviewed Journal)
    Li, Z., Zhao, B., Olk, D.C., Jia, Z., Mao, J., Cai, Y., Zhang, J. 2018. Contributions of residue-C and -N to plant growth and soil organic matter pools under planted and unplanted conditions. Soil Biology and Biochemistry. 120:91-104. https://doi.org/10.1016/j.soilbio.2018.02.005.
    
  • Structural evidence for soil organic matter turnover following glucose addition and microbial controls over soil carbon change at different horizons of a Mollisol -(Peer Reviewed Journal)
    Zhang, Y., Yao, S., Cao, X., Schmidt-Rohr, K., Olk, D.C., Mao, J., Zhang, B. 2018. Structural evidence for soil organic matter turnover following glucose addition and microbial controls over soil carbon change at different horizons of a Mollisol. Soil Biology and Biochemistry. 119:63-73. https://doi.org/10.1016/j.soilbio.2018.01.009.
    
  • Humic products in agriculture: Potential benefits and research challenges-a review -(Peer Reviewed Journal)
    Olk, D.C., Dinnes, D.L., Scoresby, R., Callaway, C.R., Darlington, J.W. 2018. Humic products in agriculture: Potential benefits and research challenges-a review. Journal of Soils and Sediments. 18:2881-2891. https://doi.org/10.1007/s11368-018-1916-4.
    
  • Nitrogen cycling under alternate wetting and drying cycles in Arkansas rice-(Abstract Only)
    
    
  • Altered humin compositions under organic and inorganic fertilization on an intensively cultivated sandy loam soil-(Peer Reviewed Journal)
    Xu, J., Zhao, B., Chu, W., Mao, J., Olk, D.C., Xin, X., Zhang, J. 2017. Altered humin compositions under organic and inorganic fertilization on an intensively cultivated sandy loam soil. Science of the Total Environment. 601-602:356-364. doi: 10.1016/j.scitotenv.2017.05.205.
    
  • Altered humin compositions under organic and inorganic fertilization on an intensively cultivated sandy loam soil-(Peer Reviewed Journal)
    Xu, J., Zhao, B., Chu, W., Mao, J., Olk, D.C., Xin, X., Zhang, J. 2017. Altered humin compositions under organic and inorganic fertilization on an intensively cultivated sandy loam soil. Science of the Total Environment. 601-602:356-364. https://doi.org/10.1016/j.scitotenv.2017.05.205.
    
  • Mechanisms of soil organic carbon accumulation from long-term fertilization strategies in two soils: Evidence from nuclear magnetic resonance spectroscopy analysis-(Peer Reviewed Journal)
    
    
  • Maximum soil organic carbon storage in Midwest U.S. cropping systems when crops are optimally nitrogen-fertilized-(Peer Reviewed Journal)
    Poffenbarger, H.J., Barker, D.W., Helmers, M.J., Miguez, F.E., Olk, D.C., Sawyer, J.E., Six, J., Castellano, M.J. 2017. Maximum soil organic carbon storage in Midwest U.S. cropping systems when crops are optimally nitrogen-fertilized. PLoS One. doi: 10.1371/journal.pone.0172293.
    
  • Enhancing soil begins with soil biology and a stable soil microclimate-(Abstract Only)
    Hatfield, J.L., Wacha, K.M., Dold, C., Cambardella, C.A., Olk, D.C., Trabue, S.L. 2017. Enhancing soil begins with soil biology and a stable soil microclimate. In: International Erosion Control Association Annual Meeting, February 21-24, 2017, Atlanta, Georgia.
    
  • Advanced solid-state NMR spectroscopy of natural organic matter-(Peer Reviewed Journal)
    Mao, J., Cao, X., Olk, D.C., Chu, W., Schmidt-Rohr, K. 2017. Advanced solid-state NMR spectroscopy of natural organic matter. Progress in Nuclear Magnetic Resonance Spectroscopy. 100:17-51. doi: 10.1016/j.pnmrs.2016.11.003.
    
  • Cropping system effects on soil organic C storage in surface and subsoils-(Abstract Only)
    Poffenbarger, H., Cambardella, C.A., Liebman, M., Mallarino, A., Olk, D.C., Six, J., Castellano, M. 2016. Cropping system effects on soil organic C storage in surface and subsoils. In: Procedings of ASA/CSSA/SSSA Annual Meeting, November 6-9, 2016, Phoenix, AZ.
    
  • Carbohydrates and amino compounds as short-term indicators of soil management -(Peer Reviewed Journal)
    Abdelrahman, H.M., Cocozza, C., Olk, D.C., Ventrella, D., Miano, T. 2017. Carbohydrates and amino compounds as short-term indicators of soil management. Clean (Soil Air Water). 45(1). doi:10.1002/clen.201600076.
    
  • Crop growth and production responses to commercial humic products in U.S. Midwestern rainfed conditions-(Abstract Only)
    
    
  • Field trials of Growmate humic products in Central and South America: benefits of networked sites.-(Abstract Only)
    
    
  • Effects of crop rotation on properties of a Vietnam clay soil under rice-based cropping systems in small-scale farmers' fields -(Peer Reviewed Journal)
    Linh, T.B., Guong, V.T., Tran, V.T., Khoa, L.V., Olk, D.C., Cornelis, W. 2016. Effects of crop rotation on properties of a Vietnam clay soil under rice-based cropping systems in small-scale farmers' fields. Soil Research. 55:162-171. doi: 10.1071/SR16123.
    
  • Occurrence and abundance of carbohydrates and amino compounds in sequentially extracted labile soil organic matter fractions.-(Peer Reviewed Journal)
    Abdelrahman, H., Olk, D.C., Dinnes, D.L., Ventrella, D., Cocozza, C. 2016. Occurrence and abundance of carbohydrates and amino compounds in sequentially extracted labile soil organic matter fractions. Journal of Soils and Sediments. 16(10):2375-2384. doi: 10.1007/s11368-016-1437-y.
    
  • Chemical compositions of dissolved organic matter from various sources as characterized by solid-state NMR-(Peer Reviewed Journal)
    Zhigao, Z., Hua, B., Xiaoyan, C., Yang, J., Olk, D.C., Baolin, D., Fengjing, L., Renying, L., Mao, J. 2015. Chemical compositions of dissolved organic matter from various sources as characterized by solid-state NMR. Aquatic Sciences - Research Across Boundaries. 77(4):595-607.
    
  • Chemical composition of defatted cottonseed and soy meal products-(Peer Reviewed Journal)
    He, Z., Zhang, H., Olk, D.C. 2015. Chemical composition of defatted cottonseed and soy meal products. PLoS One. 10(6):1-13.
    
  • Integrating plant litter quality, soil organic matter stabilization, and the carbon saturation concept-(Peer Reviewed Journal)
    Castellano, M., Mueller, K.E., Olk, D.C., Sawyer, J., Six, J. 2016. Integrating plant litter quality, soil organic matter stablilization, and the carbon saturation concept. Global Change Biology. 21:3200-3209.
    
  • Chemical composition of organic matter in a deep soil changed with a positive priming effect due to glucose addition as investigated by 13C NMR spectroscopy-(Peer Reviewed Journal)
    Zhang, Y., Yao, S., Mao, J., Olk, D.C., Cao, X., Zhang, B. 2015. Chemical composition of organic matter in a deep soil changed with a positive priming effect due to glucose addition as investigated by 13C NMR spectroscopy. Soil Biology and Biochemistry. 85:137-144.
    
  • Foliar application of plant growth-promoting bacteria and humic acid increase maize yields-(Peer Reviewed Journal)
    Canellas, L.P., Da Silva, S.F., Olk, D.C., Olivares, F.L. 2015. Foliar application of plant growth-promoting bacteria and humic acid increase maize yields. Journal of Food, Agriculture and Environment. 13:131-138.
    
  • Can humic products become mainstream amendments for improving crop production?-(Abstract Only)
    
    
  • Water-conserving practices in Arkansas rice production to improve soil N availability and reduce greenhouse gas emissions-(Abstract Only)
    
    
  • Protein and fiber profiles of cottonseed from upland cotton with different fertilizations -(Peer Reviewed Journal)
    He, Z., Zhang, H., Olk, D.C., Shankle, M., Way, T.R., Tewolde, H. 2014. Protein and fiber profiles of cottonseed from upland cotton with different fertilizations. Modern Applied Science. 8(4):97-105.
    
  • Soil amino compound and carbohydrate contents influenced by organic amendments-(Book / Chapter)
    He, Z., Olk, D.C., Waldrip, H.M. 2014. Soil amino compound and carbohydrate contents influenced by organic amendments. In: He, Z., Zhang, H., editors. Applied Manure and Nutrient Chemistry for Sustainable Agriculture and Environment. Amsterdam, the Netherlands: Springer. p. 69-82.
    
  • Determination of humic and fulvic acids in commercial solid and liquid humic products by alkaline extraction and gravimetric determination-(Peer Reviewed Journal)
    Lamar, R.T., Olk, D.C., Mayhew, L., Bloom, P.R. 2014. Determination of humic and fulvic acids in commercial solid and liquid humic products by alkaline extraction and gravimetric determination. Journal of AOAC International. 97(3):721-730.
    
  • Kinetics of short-term root-carbon mineralization in roots of biofuel crops in soils -(Peer Reviewed Journal)
    Rivas, F.A., Tabatabai, M.A., Olk, D.C., Thompson, M.L. 2014. Kinetics of short-term root-carbon mineralization in roots of biofuel crops in soils. Biology and Fertility of Soils. 50(3):527-535.
    
  • Similarities in chemical composition of soil organic matter across a millennia-old paddy soil chronosequence as revealed by advanced solid-state NMR spectroscopy -(Peer Reviewed Journal)
    Zhou, Z., Cao, X., Schmidt-Rohr, K., Olk, D.C., Zhuang, S., Zhou, J., Cao, Z., Mao, J. 2014. Similarities in chemical composition of soil organic matter across a millenia-old paddy soil chronosequence as revealed by advanced solid-state NMR spectroscopy. Biology and Fertility of Soils. 50:571-581.
    
  • On-farm evaluation of a humic product in Iowa (U.S.) maize production-(Book / Chapter)
    Olk, D.C., Dinnes, D.L., Callaway, C., Raske, M. 2013. On-farm evaluation of a humic product in Iowa (U.S.) maize production. In: Xu, J., Wu, J., He, Z., editors. Functions of Natural Organic Matter in a Changing Environment. Dordrecht, The Netherlands: Springer. p. 1047-1050.
    
  • Evaluation of a proposed standardized analytical method for the determination of humic and fulvic acids in commercial products-(Book / Chapter)
    Lamar, R., Olk, D.C., Mayhew, L., Bloom, P.R. 2013. Evaluation of a proposed standardized analytical method for the determination of humic and fulvic acids in commercial products. In: Xu, J., Wu, J., He, Z., editors. Functions of Natural Organic Matter in a Changing Environment. Dordrecht, The Netherlands: Springer. p. 1071-1073.
    
  • Integrated physical-chemical procedure for soil organic carbon frationation and characterization during transition to organic farming-(Book / Chapter)
    Abdelrahman, H.M., Olk, D.C., Cocozza, C., Ventrella, D., Montemurro, F.P., Miano, T. 2013. Integrated physical-chemical procedure for soil organic carbon frationation and characterization during transition to organic farming. In: Xu, J., Wu, J., He, Z., editors. Functions of Natural Organic Matter in a Changing Environment. Dordrecht, The Netherlands: Springer. p. 73-77.
    
  • Chemical properties of humic and fulvic acid products and their ores of origin-(Book / Chapter)
    Mao, J., Olk, D.C., Na, C., Dinnes, D.L., Chappell, M. 2013. Chemical properties of humic and fulvic acid products and their ores of origin. In: Xu, J., Wu, J., He, Z., editors. Functions of Natural Organic Matter in a Changing Environment. Dordrecht, The Netherlands: Springer. p. 1067-1070.
    
  • Abundant and stable char residues in soils: Implications for soil fertility and carbon sequestration-(Book / Chapter)
    Mao, J., Johnson, R.L., Lehmann, J., Olk, D.C., Neves, E.G., Thompson, M.L., Schmidt-Rohr, K. 2013. Abundant and stable char residues in soils: Implications for soil fertility and carbon sequestration. In: Xu, J., Wu, J., He, Z., editors. Functions of Natural Organic Matter in a Changing Environment. Dordrecht, The Netherlands: Springer. p. 479-484.
    
  • Degree of woody encroachment into grasslands controls soil carbohydrate and amino compound changes during long-term laboratory incubation-(Peer Reviewed Journal)
    Creamer, C.A., Filley, T.R., Olk, D.C., Plant, A., Peltre, C., Top, S.M., Boutton, T.W. 2012. Degree of woody encroachment into grasslands controls soil carbohydrate and amino compound changes during long-term laboratory incubation. Organic Geochemistry. 52:23-31. Available: http://www.sciencedirect.com/science/article/pii/S0146638012001714.
    
  • Abundant and stable char residues in soils: Implications for soil fertility and carbon sequestration-(Peer Reviewed Journal)
    Mao, J., Johnson, R.L., Lehmann, J., Olk, D.C., Neves, E.G., Thompson, M.L., Schmidt-Rohr, K. 2012. Abundant and stable char residues in soils: Implications for soil fertility and carbon sequestration. Environmental Science and Technology. 46(17):9571-9576.
    
  • Fall conservation deep tillage stabilizes maize residues into soil organic matter-(Peer Reviewed Journal)
    Wingeyer, A.B., Walters, D., Drijber, R., Olk, D.C., Arkebauer, T., Verma, S., Wedin, D., Francis, C. 2012. Fall conservation deep tillage stabilizes maize residues into soil organic matter. Soil Science Society of America Journal. 76(6):2154-2163.
    
  • Changes to soil organic N dynamics with leguminous woody plant encroachment into grasslands-(Peer Reviewed Journal)
    Creamer, C.A., Filley, T.R., Olk, D.C., Stott, D.E., Dooling, V., Boutton, T.W. 2012. Changes to soil organic N dynamics with leguminous woody plant encroachment into grasslands. Biogeochemistry. 113(1-3):307-321. DOI:10.1007/s10533-012-9757-5.
    
  • Relating soil biochemistry to sustainable crop production-(Abstract Only)
    
    
  • Field evaluation of a humic product in Iowa corn fields-(Abstract Only)
    
    
  • Rice rotation and tillage effects on soil aggregation and aggregate carbon and nitrogen dynamics-(Peer Reviewed Journal)
    Anders, M.M., Brye, K.R., Olk, D.C., Schmid, B.T. 2012. Rice rotation and tillage effects on soil aggregation and aggregate carbon and nitrogen dynamics. Soil Science Society of America Journal. 76(3):994-1004.
    
  • Yields of potato and alternative crops impacted by humic product application-(Book / Chapter)
    Seyedbagheri, M., He, Z., Olk, D.C. 2012. Yields of potato and alternative crops impacted by humic product application. In: He, Z., Larkin, R.P., Honeycutt, C.W., editors. Sustainable Potato Production: Global Case Studies. Amsterdam, The Netherlands: Springer. p. 131-140.
    
  • Quantities and qualities of physical and chemical fractions of soil organic matter under a rye cover crop-(Abstract Only)
    Olk, D.C., Cambardella, C.A., Kaspar, T.C. 2011. Quantities and qualities of physical and chemical fractions of soil organic matter under a rye cover crop. American Society of Agronomy Annual Meetings [abstracts]. ASA-CSSA-SSSA Annual Meeting. Oct. 16-19, 2011, San Antonio, TX. CD-ROM.
    
  • Types of Carbon Compounds That Accumulate Under No-Tillage In Rice-Based Rotations-(Abstract Only)
    Olk, D.C., Anders, M.M. 2011. Types of Carbon Compounds That Accumulate Under No-Tillage In Rice-Based Rotations.American Society of Agronomy Annual Meetings [abstracts]. ASA-CSSA-SSSA Annual Meeting. Oct. 16-19, 2011, San Antonio, TX. CD-ROM.
    
  • Impacts of humic product application on yields of potato and other field crops-(Abstract Only)
    Olk, D.C., Mosa, A.M., Waldrip, H. 2011. Impacts of humic product application on yields of potato and other field crops. American Society of Agronomy Annual Meetings [abstracts]. ASA-CSSA-SSSA Annual Meeting. Oct. 16-19, 2011, San Antonio, TX. CD-ROM.
    
  • Changes in soil amino composition and microbial N acquisition strategies in response to woody plant invasion of grasslands-(Abstract Only)
    Creamer, C.A., Filley, T.R., Boutton, T.W., Stott, D.E., Olk, D.C. 2011. Changes in soil amino composition and microbial N acquisition strategies in response to woody plant invasion of grasslands [abstract]. ASA-CSSA-SSSA International Annual Meeting in conjunction with the Canadian Society of Soil Science, October 16-19, 2011, San Antonio, Texas. 2011 CDROM.
    
  • Solid-state NMR analysis of soil organic matter fractions from integrated physical-chemical extraction-(Peer Reviewed Journal)
    Cao, X., Olk, D.C., Chappell, M., Cambardella, C.A., Miller, L.F., Mao, J. 2011. Solid-state NMR analysis of soil organic matter fractions from integrated physical-chemical extraction. Soil Science Society of America Journal. 75(4):1374-1384.
    
  • Forms and Lability of Phosphorus in Humic Acid Fractions of Hord Silt Loam Soil-(Peer Reviewed Journal)
    He, Z., Olk, D.C., Cade-Menun, B.J. 2011. Forms and lability of phosphorus in humic acid fractions of hord silt loam soil. Soil Science Society of America Journal. 75:1712-1722.
    
  • Amino acid composition of a manure-amended soil: rhizospheric and non-rhizospheric differences in a greenhouse ryegrass study-(Abstract Only)
    Olk, D.C., He, Z., Waldrip, H. 2010. Amino acid composition of a manure-amended soil: rhizospheric and non-rhizospheric differences in a greenhouse ryegrass study [abstracts]. ASA-CSSA-SSSA Annual Meeting. Oct. 31 - Nov. 4, 2010, Long Beach, CA. CD-ROM
    
  • Seasonal Shifts in the Biochemical Compoments of the Light Fraction, Particulate Organic Matter, and Two Humic Acid Fractions in An Iowa Soil-(Abstract Only)
    Olk, D.C., Cambardella, C.A., Kaspar, T.C. 2010. Seasonal Shifts in the Biochemical Compoments of the Light Fraction, Particulate Organic Matter, and Two Humic Acid Fractions in An Iowa Soil. American Society of Agronomy Annual Meetings [abstracts]. ASA-CSSA-SSSA Annual Meeting. Oct. 31 - Nov. 4, 2010, Long Beach, CA. CD-ROM.
    
  • Manure amino acid compounds and their bioavailability-(Book / Chapter)
    He, Z., Olk, D.C. 2011. Manure amino acid compounds and their bioavailability. In: He, Z., editor. Environmental Chemistry of Animal Manure. New York, NY: Nova Science Publishers. p. 179-199.
    
  • Chemical structure of soil organic matter in slickspots as investigated by advanced solid-state NMR-(Peer Reviewed Journal)
    Mao, J., Palazzo, D.C., Olk, D.C., Clapp, C.E., Senesi, N., Bushore, T.I., Cao, X. 2010. Chemical structure of soil organic matter in slickspots as investigated by advanced solid-state NMR. Soil Science. 175:329-338.
    
  • Field Evaluations of Commercial Humic Products: Current Knowledge and Future Needs.-(Other)
    
    
  • Aerobic Decomposition and Organic Amendments Effects on Grain Yield of Triple-Cropped Rice in the Mekong Delta, Vietnam-(Abstract Only)
    Guong, V.T., Nguyen, H.D., Merckx, R., Olk, D.C. 2010. Aerobic Decomposition and Organic Amendments Effects on Grain Yield of Triple-Cropped Rice in the Mekong Delta, Vietnam [abstract]. World Congress of Soil Science, August 1-6, 2010, Brisbane, Queensland, Australia, CD-ROM.
    
  • Capillary Electrophoresis Profiles and Fluorophore Components of Humic Acids in Nebraska Corn and Philippine Rice Soils-(Peer Reviewed Journal)
    He, Z., Ohno, T., Olk, D.C., Wu, F. 2010. Capillary Electrophoresis Profiles and Fluorophore Components of Humic Acids in Nebraska Corn and Philippine Rice Soils. Geoderma. 156:143-175.
    
  • Linkages Between Land Cover, Enzymes, and Soil Organic Matter Chemistry Following Encroachment of Leguminous Woody Plant into Grasslands-(Proceedings)
    Filley, T.R., Stott, D.E., Boutton, T.W., Creamer, C., Olk, D.C. 2009. Linkages Between Land Cover, Enzymes, and Soil Organic Matter Chemistry Following Encroachment of Leguminous Woody Plant into Grasslands. Eos, Transactions of the American Geophysical Union 90(52): B21B-0338.
    
  • Characterization of humic-bound phosphorus in soil by wet chemistry and solution P-31 NMR spectroscopy-(Abstract Only)
    He, Z., Honeycutt, C.W., Olk, D.C., Cade-Menun, B.J. 2009. Characterization of humic-bound phosphorus in soil by wet chemistry and solution P-31 NMR spectroscopy. Soil Science Society of America Annual Meeting. On-line publication.
    
  • Landscape-Scale Evaluation of a Humic Product in An Iowa Corn Region-(Abstract Only)
    Rhodes, B., Raske, M., Olk, D.C. 2009. Landscape-Scale Evaluation of a Humic Product in An Iowa Corn Region [Abstract]. In: ASA-CSSA-SSSA Annual Meeting Abstracts, Nov. 1-5, 2009, Pittsburgh, PA.
    
  • Overview of the Humic Amendments Session: Current and Future Challenges for the Industry and Researchers-(Abstract Only)
    Olk, D.C. 2009. Overview of the Humic Amendments Session: Current and Future Challenges for the Industry and Researchers [CD-ROM]. In: ASA-CSSA-SSSA Annual Meeting Abstracts, Nov. 1-5, 2009, Pittsburgh, PA.
    
  • Advanced 13C NMR Analysis of the Light Fraction, Particulate Organic Matter, and Humic Acid Fractions From a Corn-Soybean Soil-(Abstract Only)
    Mao, J., Olk, D.C., Li, Y. 2009. Advanced 13C NMR Analysis of the Light Fraction, Particulate Organic Matter, and Humic Acid Fractions From a Corn-Soybean Soil [Abstract]. In: ASA-CSSA-SSSA Annual Meeting Abstracts, Nov. 1-5, 2009, Pittsburgh, PA.
    
  • Enzymatically- and Ultraviolet-labile Phosphorus in Humic Acid Fractions From Rice Soils-(Peer Reviewed Journal)
    He, Z., Olk, D.C., Honeycutt, C.W., Fortuna, A. 2009. Enzymatically- and Ultraviolet-labile Phosphorus in Humic Acid Fractions From Rice Soils. Soil Science. 174(2):81-87.
    
  • Organic forms of soil nitrogen-(Abstract Only)
    Olk, D.C. 2008. Organic forms of soil nitrogen [CD-ROM]. In: ASA-CSSA-SSSA Annual Meeting Abstracts, Oct. 5-9, 2008, Houston, TX.
    
  • Characterization of manure from conventional and phytase transgenic pigs by advanced solid-state NMR spectroscopy-(Abstract Only)
    Mao, J., Ajakaiye, A., Olk, D.C., Ceballos, M., Zhang, T., Fan, M.Z., Forsberg, C.W. 2008. Characterization of manure from conventional and phytase transgenic pigs by advanced solid-state NMR spectroscopy [CD-ROM]. In: ASA-CSSA-SSSA Annual Meeting Abstracts, Oct. 5-9, 2008, Houston, TX.
    
  • Soil N cycling and phenols accumulation under continuous rice cropping in the Grand Prairie region, Arkansas-(Peer Reviewed Journal)
    Olk, D.C., Anders, M.M., Filley, T.R., Isbell, C. 2009. Soil N cycling and phenols accumulation under continuous rice cropping in the Grand Prairie region, Arkansas. Soil Science Society of America Journal. 73(3):952-960.
    
  • Influence of animal manure application on the chemical structures of soil organic matter as investigated by advanced solid-state NMR and FT-IR spectroscopy-(Peer Reviewed Journal)
    Mao, J., Olk, D.C., Fang, X., He, Z., Schmidt-Rohr, K. 2008. Influence of animal manure application on the chemical structures of soil organic matter as investigated by advanced solid-state NMR and FT-IR spectroscopy. Geoderma. 146(1-2)353-362.
    
  • Using anion chromatography-pulsed amperometry to meaasure amino compounds in dairy manure-amended soils-(Peer Reviewed Journal)
    Olk, D.C., Fortuna, A., Honeycutt, C.W. 2008. Using anion chromatography-pulsed amperometry to measure amino compounds in dairy manure-amended soils. Soil Science Society of America Journal. 72(6):1711-1720.
    
  • Capillary Electrophoresis and Fluorescence Excitation-Emission Matrix Characterization of Soil Mobile and Calcium Humates-(Proceedings)
    He, Z., Ohno, T., Olk, D.C., Wu, F., Honeycutt, C.W., Mao, J. 2008. Capillary Electrophoresis and Fluorescence Excitation-Emission Matrix Characterization of Soil Mobile and Calcium Humates. International Humic Substances Society Conference. From molecular understanding to innovative applications of humic substances, Vol. I. Humus Sapiens, Moscow, Russia.
    
  • Improved analyses for soil carbohydrates, amino acids, and phenols: Tools for understanding soil processes-(Peer Reviewed Journal)
    Olk, D.C. 2008. Improved analyses for soil carbohydrates, amino acids, and phenols: Tools for understanding soil processes. Soil Science Society of America Journal. 72(6):1672-1682.
    
  • Lability of Humic-Bound Phosphorus-(Abstract Only)
    He, Z., Honeycutt, C.W., Olk, D.C. 2008. Lability of Humic-Bound Phosphorus. Humic Science and Technology Conference Abstract. p. 52.
    
  • Phenol accumulation in a young humic fraction following anaerobic decomposition of rice crop residues-(Peer Reviewed Journal)
    Olk, D.C., Jimenez, R.R., Moscoso, E., Gapas, P. 2009. Phenol accumulation in a young humic fraction following anaerobic decomposition of rice crop residues. Soil Science Society of America Journal. 73(3):943-951.
    
  • Capillary Electrophoresis and Fluorescence Excitation-Emission Matrix Spectroscopy for Characterization of Humic Substances-(Peer Reviewed Journal)
    He, Z., Ohno, T., Wu, F., Olk, D.C., Honeycutt, C.W., Olanya, O.M. 2008. Capillary Electrophoresis and Fluorescence Excitation-Emission Matrix Spectroscopy for Characterization of Humic Substances. Soil Science Society of America Journal. 72:1248-1255.
    
  • Some Contributions of Resistant Compounds to Soil Organic Matter Formation and Nutrient Cycling-(Abstract Only)
    Olk, D.C., Laird, D.A., Thompson, M.L. 2007. Some Contributions of Resistant Compounds to Soil Organic Matter Formation and Nutrient Cycling [CD-ROM]. In: ASA-CSSA-SSSA Annual Meeting Abstracts. Nov. 4-8, 2007, New Orleans, LA.
    
  • Advanced Solid-State 13C NMR Analysis of Organic Matter in a Nebraska Corn Soil Amended with Cattle Manure-(Abstract Only)
    Mao, J., Olk, D.C., Gleason, J. 2007. Advanced Solid-State 13C NMR Analysis of Organic Matter in a Nebraska Corn Soil Amended with Cattle Manure [CD-ROM]. In: ASA-CSSA-SSSA Annual Meeting Abstracts, Nov. 4-8, 2007, New Orleans, LA.
    
  • Aerobic decomposition of crop residues improves N availability and grain yield for three rice soils of the Mekong Delta, Vietnam: A screenhouse study-(Abstract Only)
    Trang, T.T., Guong, V.T., Olk, D.C., Vien, D.M., Dong, N.M., Merckx, R. 2007. Aerobic decomposition of crop residues improves N availability and grain yield for three rice soils of the Mekong Delta, Vietnam: A screenhouse study [CD-ROM]. In: ASA-CSSA-SSSA Annual Meeting Abstracts, Nov. 4-8, 2007, New Orleans, LA.
    
  • Chemical Structures of Feces from Conventional and Phytase Transgenic Pigs Investigated by Advanced Solid-State NMR Spectroscopy-(Peer Reviewed Journal)
    Mao, J.D., Zhang, T., Lan, Y., Olk, D.C., Ding, G., Ceballos, M. 2008. Chemical Structures of Feces from Conventional and Phytase Transgenic Pigs Investigated by Advanced Solid-State NMR Spectroscopy. Journal of Agricultural and Food Chemistry. 56(6):2131-2138.
    
  • Analysis of Phosphorus in Soil Humic Acid Fractions by Enzymatic Hydrolysis and Ultraviolet Irradiation-(Abstract Only)
    He, Z., Olk, D.C., Honeycutt, C.W., Fortuna, A., Ohno, T. 2007. Analysis of Phosphorus in Soil Humic Acid Fractions by Enzymatic Hydrolysis and Ultraviolet Irradiation. Soil Science Society of America Annual Meeting. CD-ROM
    
  • Characterization of IHSS Natural Organic Matter by Capillary Electrophoresis and Flourescence Spectroscopy-(Abstract Only)
    He, Z., Ohno, T., Wu, F., Olk, D.C., Honeycutt, C.W., Olanya, O.M. 2007. Characterization of IHSS Natural Organic Matter by Capillary Electrophoresis and Flourescence Spectroscopy. American Chemical Society Abstracts. 10th Anniversary Humic Science and Technology Conference Abstracts; page 27
    
  • Analyses developed by Dean Martens for soil carbohydrates, phenols, and amino compounds: Tools for understanding soil processes-(Abstract Only)
    Olk, D.C. 2006. Analyses developed by Dean Martens for soil carbohydrates, phenols, and amino compounds: Tools for understanding soil processes [CD-ROM]. In: ASA-CSSA-SSSA Annual Meeting Abstracts, Nov. 12-16, Indianapolis, IN.
    
  • Using anion chromatography-pulsed amperometry to measure amino compounds in animal manure-amended soil-(Abstract Only)
    Olk, D.C., Fortuna, A., Honeycutt, C.W. 2006. Using anion chromatography-pulsed amperometry to measure amino compounds in animal manure-amended soil [CD-ROM]. In: ASA-CSSA-SSSA Annual Meeting Abstracts, Nov. 12-16, 2006, Indianapolis, IN.
    
  • Response to "Comments on 'Need for a Soil-based Approach in managing Nitrogen Fertilizers for Profitable Corn Production' and 'Soil Organic Nitrogen Enrichment Following Soybean in an Iowa Corn-Soybean Rotation'"-(Other)
    Jaynes, D.B., Olk, D.C., Colvin, T., Kaspar, T.C., Karlen, D.L. 2007. Response to "Comments on 'Need for a Soil-based Approach in managing Nitrogen Fertilizers for Profitable Corn Production' and 'Soil Organic Nitrogen Enrichment Following Soybean in an Iowa Corn-Soybean Rotation'". Soil Science Society of America Journal. 71(1):255.
    
  • INHIBITION OF NITROGEN MINERALIZATION IN YOUNG HUMIC FRACTIONS BY ANAEROBIC DECOMPOSITION OF RICE CROP RESIDUES-(Peer Reviewed Journal)
    Olk, D.C., Samson, M.I., Gapas, P. 2007. Inhibition of nitrogen mineralization in young humic fractions by anaerobic decomposition of rice crop residues. European Journal of Soil Science. 58:270-281.
    
  • SOME BIOLOGICAL, CHEMICAL, AND PHYSICAL FRACTIONATION PROCEDURES FOR SOIL ORGANIC MATTER-(Abstract Only)
    Olk, D.C., Gregorich, E.G., Farenhorst, A., Hayes, M., Paul, E.A., Simpson, M.J. 2006. Some biological, chemical, and physical fractionation procedures for soil organic matter. In: Proceedings of the 13th Meeting of the International Humic Substances Society. 45(1):21-24.
    
  • CAN WE IDENTIFY MEANINGFUL FRACTIONS OF SOIL ORGANIC MATTER?-(Other)
    Olk, D.C. 2006. Can we identify meaningful fractions of soil organic matter? Crop Science Newsletter. 51(6):4-5.
    
  • ORGANIC FORMS OF NITROGEN-(Book / Chapter)
    Olk, D.C. 2007. Organic Forms of Nitrogen. In: Carter, M.R., Gregorich, E.G., editors. Soil Sampling and Methods of Analysis. 2nd Edition. Boca Raton, FL: Taylor & Francis Group, CRC Press. p. 667-674.
    
  • A CHEMICAL FRACTIONATION FOR STRUCTURE-FUNCTION RELATIONS OF SOIL ORGANIC MATTER IN NUTRIENT CYCLING-(Peer Reviewed Journal)
    Olk, D.C. 2006. A chemical fractionation for structure-function relations of soil organic matter in nutrient cycling. Soil Science Society of America Journal. 70(3) 1013-1022.
    
  • SIX DECADES OF SOIL ORGANIC MATTER STUDY: THE HISTORY OF NCERA-59-(Abstract Only)
    Allan, D., Archibald, D., Cihacek, L., Dick, R., Drijber, R., Frey, S., Horwath, W., Motavalli, P., Olk, D.C., Rice, C., Snapp, S., Stone, A., Turco, R., Wander, M., Weil, R. 2006. Six decades of soil organic matter study: the history of NCERA-59. In: Proceedings of the World Congress of Soil Science, July 9-15, 2006, Philadelphia, PA. 2006 CD-ROM.
    
  • CHEMICAL STABILIZATION OF SOIL NITROGEN BY PHENOLIC LIGNIN RESIDUES IN ANAEROBIC AGRO-ECOSYSTEMS-(Abstract Only)
    Olk, D.C. 2005. Chemical stabilization of soil nitrogen by phenolic lignin residues in anaerobic agro-ecosystems. 6th Meeting of the Brazilian Substances Society [abstract]. p. P 36-38.
    
  • SHORT-AND LONG-TERM EFFECTS OF ROTATION AND TILLAGE ON SOIL AGGREGATE STABILITY AND RESISTANCE-(Abstract Only)
    Anders, A.A., Schmid, B., Olk, D.C. 2005. Short-and long-term effects of rotation and tillage on soil aggregate stability and resistance [CD-ROM]. In: ASA-CSSA-SSSA Annual Meeting Abstracts, Nov. 6-10, 2005, Salt Lake City, UT.
    
  • LONG-TERM CHANGES IN SOIL NITROGEN SUPPLYING CAPACITY IN RICE-MAIZE AND RICE-RICE CROPPING SYSTEMS-(Abstract Only)
    Buresh, R.J., Lazaro, W.M., Pampolino, M.F., Dizon, M.A., Olk, D.C., Witt, C. 2005. Long-term changes in soil nitrogen supplying capacity in rice-maize and rice-rice cropping systems [CD-ROM]. In: ASA-CSSA-SSSA Annual Meeting Abstracts, Nov. 6-10, 2005, Salt Lake City, UT.
    
  • COMPARISON OF CUO OXIDATION AND TMAH FOR MEASURING PHENOLS IN HUMIC SAMPLES-(Abstract Only)
    Filley, T.R., Gamblin, D., Olk, D.C. 2005. Comparison of CUO oxidation and TMAH for measuring phenols in humic samples [CD-ROM]. In: ASA-CSSA-SSSA Annual Meeting Abstracts, Nov. 6-10, 2005, Salt Lake City, UT.
    
  • TREE SPECIES DIFFER IN THEIR LONG-TERM EFFECTS ON SOIL CARBON DYNAMICS AND BIOCHEMISTRY IN LOWLAND COSTA RICA-(Abstract Only)
    Russell, A., Olk, D.C., Marek, R., Fisher, R., Raich, J. 2005. Tree species differ in their long-term effects on soil carbon dynamics and biochemistry in lowland Costa Rica [CD-ROM]. In: ASA-CSSA-SSSA Annual Meeting Abstracts, Nov. 6-10, 2005, Salt Lake City, UT.
    
  • INHIBITED UPTAKE OF SOIL N AND ITS YIELD IMPACT FOR CONTINUOUS RICE CROPPING IN ARKANSAS-(Abstract Only)
    Olk, D.C., Anders, M.M. 2005. Inhibited uptake of soil N and its yield impact for continuous rice cropping in Arkansas [CD-ROM]. In: ASA-CSSA-SSSA Annual Meeting Abstracts, Nov. 6-10, 2005, Salt Lake City, UT.
    
  • OVERVIEW OF THE SYMPOSIUM PROCEEDINGS, "MEANINGFUL POOLS IN DETERMINING SOIL C AND N DYNAMICS"-(Peer Reviewed Journal)
    Olk, D.C., Gregorich, E.G. 2006. Overview of the symposium proceedings, "Meaningful pools in determining soil C and N dynamics". Soil Science Society of America Journal. 70(3): 967-974.
    
  • CHEMICAL STABILIZATION OF SOIL ORGANIC NITROGEN BY PHENOLIC LIGNIN RESIDUES IN ANAEROBIC AGROSYSTEMS-(Peer Reviewed Journal)
    Olk, D.C., Cassman, K.G., Schmidt-Rohr, K., Anders, M.M., Mao, J.D., Deenik, J.L. 2006. Chemical stabilization of soil organic nitrogen by phenolic lignin residues in anaerobic agrosystems. Soil Biology and Biochemistry. 38(11):3303-3312.
    
  • SHORT AND LONG TERM EFFECTS OF CONSERVATION TILLAGE ON SOIL RESISTANCE AND AGGREGATE STABILITY IN RICE PRODUCTION SYSTEMS.-(Proceedings)
    Anders, M.M., Schmid, B., Olk, D.C. 2005. Short and long term effects of conservation tillage on soil resistance and aggregate stability in rice production systems. Proceedings of the 27th Annual Southern Conservation Tillage Systems Conference. p. 102-110.
    
  • TREE SPECIES OF MOIST TROPICAL FORESTS DIFFER IN THEIR DETRITAL BIOCHEMISTRY AND EFFECTS ON SOIL CARBON DYNAMICS-(Abstract Only)
    Russell, A.E., Olk, D.C., Marek, R.F. 2005. Tree species of moist tropical forests differ in their detrital biochemistry and effects on soil carbon dynamics. In: Ecological Society of America Proceedings. Ecological Society of America 90th Annual Meeting, Aug. 7-12, 2005, Montreal, Canada. p. 554.
    
  • Integrated Nutrient Management: Experience from rice-based systems in Southeast Asia-(Book / Chapter)
    Olk, D.C., Becker, M., Linquist, B.A., Pandey, S., Witt, C. 2008. Integrated Nutrient Management: Experience from rice-based systems in Southeast Asia. In: Aulakh, M.S. and Grant, C.A., editors. Integrated Nutrient Management for Sustainable Crop Production. Haworth Press/Taylor & Francis. New York, NY. p. 369-420.
    
  • DOES ANAEROBIC DECOMPOSITION OF CROP RESIDUES IMPAIR SOIL NITROGEN CYCLING AND YIELD TRENDS IN LOWLAND RICE?-(Proceedings)
    Olk, D.C., Cassman, K.G., Anders, M.M., Schmidt-Rohr, K., Mao, J.D. 2005. Does anaerobic decomposition of crop residues impair soil nitrogen cycling and yield trends in lowland rice? [CD-ROM] Proceedings of the World Rice Research Conference, Nov. 4-7, 2004, Tokyo and Tsukuba, Japan. p. 374-377.
    
  • CHEMICAL STABILIZATION OF SOIL ORGANIC NITROGEN BY PHENOLIC LIGNIN COMPOUNDS IN ANAEROBIC AGROSYSTEMS-(Abstract Only)
    Olk, D.C. 2004. Chemical stabilization of soil organic nitrogen by phenolic lignin compounds in anaerobic agrosystems [CD-ROM]. American Geophysical Union. Paper No. 5896. Washington, D.C.
    
  • TRIGGERING OF METHANE PRODUCTION IN RICE SOILS BY ROOT EXUDATES: EFFECTS OF SOIL PROPERTIES AND CROP MANAGEMENT-(Peer Reviewed Journal)
    Mitra, S., Aulakh, M.S., Wassmann, R., Olk, D.C. 2005. Triggering of Methane Production in Rice Soils by Root Exudates: Effects of Soil Properties and Crop Management. Soil Science Society of America Journal. 69:556-570.
    
  • A CHEMICAL FRACTIONATION FOR STRUCTURE-FUNCTION RELATIONS OF SOIL ORGANIC MATTER IN NUTRIENT CYCLING-(Abstract Only)
    Olk, D.C. 2004. A chemical fractionation for structure-function relations of soil organic matter in nutrient cycling [CD-ROM]. ASA-CSSA-SSSA Annual Meeting Abstracts. Madison, WI.
    
  • EFFECT OF ROTATION, TILLAGE, AND FERTILITY ON RICE YIELD AND NUTRIENT CYCLING-(Abstract Only)
    Anders, M.M., Olk, D.C., Holzhauer, J. 2004. Effect of rotation, tillage, and fertility on rice yield and nutrient cycling [CD-ROM]. ASA-CSSA-SSSA Annual Meeting Abstracts. Madison, WI.
    
  • LONG-TERM MANAGEMENT EFFECTS ON THE MOBILE HUMIC ACID FRACTION-(Abstract Only)
    Legorreta, F., Walters, D.T., Olk, D.C., Madhavan, S., Cassman, K.G. 2004. Long-term management effects on the mobile humic acid fraction [CD-ROM]. ASA-CSSA-SSSA Annual Meeting Abstracts. Madison, WI.
    
  • THE EFFECT OF ROTATION, TILLAGE, AND FERTILITY ON RICE GRAIN YIELDS AND NUTRIENT FLOWS-(Proceedings)
    Anders, M.M., Olk, D.C., Harper, T., Daniel, T., Holzhauer, J. 2004. The effect of rotation, tillage, and fertility on rice grain yields and nutrient flows [CD-ROM]. TB-321. Raleigh, NC. North Carolina Agricultural Research Service Technical Bulletin.
    
  • DOES ANAEROBIC DECOMPOSITION OF CROP RESIDUES ALTER SOIL ORGANIC MATTER QUALITY AND NUTRIENT CYCLING?-(Abstract Only)
    Olk, D.C. 2004. In: L. Martin-Meto, D. Milori, and W. da Silva. Humic Substances and Soil Water Environment EMBRAPA Instrumentacao Agropecuaria. Does Anaerobic Decomposition of Crop Residues Alter Soil Organic Matter Quality and Nutrient Cycling? International Humic Substances Society Conference. p. 615-617.
    
  • NITROGEN-BONDED AROMATICS IN SOIL ORGANIC MATTER AND THEIR IMPLICATIONS FOR A YIELD DECLINE IN INTENSIVE RICE CROPPING-(Peer Reviewed Journal)
    Schmidt-Rohr, K., Mao, J.D., Olk, D.C. 2004. Nitrogen-bonded aromatics in soil organic matter and their implications for a yield decline in intensive rice cropping. Proceedings Of The National Academy Of Sciences. 101(17):6351-6354.
    
  • IMPAIRED CYCLING OF SOIL NITROGEN UNDER CONTINUOUS RICE ROTATIONS IN THE ARKANSAS GRAND PRAIRIE AREA-(Abstract Only)
    Olk, D.C., Anders, M.M., Boeckmann, J.M., Grantham, J., Holzhauer, J. 2005. Impaired cycling of soil nitrogen under continuous rice rotations in the arkansas grand prairie area. Rice Technical Working Group Meeting Proceedings. p. 148-149.
    
  • EFFECTS OF ROTATION, TILLAGE, FERTILITY, AND VARIETY ON RICE GRAIN YIELD AND NUTRIENT UPTAKE-(Abstract Only)
    Anders, M.M., Olk, D.C., Grantham, J., Holzhauer, J. 2005. Effects of rotation, tillage, fertility, and variety on rice grain yield and nutrient uptake. Rice Technical Working Group Meeting Proceedings. P. 159-160.
    
  • NITROGEN MINERALIZATION FROM HUMIC ACID FRACTIONS IN RICE SOILS DEPENDS ON DEGREE OF HUMIFICATION-(Peer Reviewed Journal)
    Nguyen, B.V., Olk, D.C., Cassman, K.G. 2004. Nitrogen mineralization from humic acid fractions in rice soils depends on degree of humification. Soil Science Society of America Journal. 68:1278-1284.
    
  • CHARACTERIZATION OF HUMIC ACID FRACTIONS IMPROVES ESTIMATES OF NITROGEN MINERALIZATION KINETICS FOR LOWLAND RICE SOILS-(Peer Reviewed Journal)
    Nguyen, B., Olk, D.C., Cassman, K.G. 2004. Characterization of humic acid fractions improves estimates of nitrogen mineralization kinetics for lowland rice soils. Soil Science Society of America Journal. 68:1266-1277.
    
  • DOES ANAEROBIC DECOMPOSITION OF CROP RESIDUES ALTER NUTRIENT CYCLING AND SOIL ORGANIC MATTER QUALITY?-(Abstract Only)
    OLK, D.C. DOES ANAEROBIC DECOMPOSITION OF CROP RESIDUES ALTER NUTRIENT CYCLING AND SOIL ORGANIC MATTER QUALITY?. ASA-CSSA-SSSA PROCEEDINGS. 2003. CD-ROM. MADISON, WI. ASA-CSSA-SSSA.
    
  • DETECTION OF AROMATIC-BONDED N AND ASSOCIATED LIGNIN RESIDUES IN A HUMIC FRACTION BY ADVANCED SOLID-STATE NMR-(Abstract Only)
    MAO, J., OLK, D.C., SCHMIDT-ROHR, K. DETECTION OF AROMATIC-BONDED N AND ASSOCIATED LIGNIN RESIDUES IN A HUMIC FRACTION BY ADVANCED SOLID-STATE NMR. ASA-CSSA-SSSA PROCEEDINGS. 2003. CD-ROM. MADISON, WI. ASA-CSSA-SSSA.
    
  • SOIL AND PLANT NITROGEN CYCLING UNDER TILLAGE PRACTICES IN RICE-BASED ROTATIONS IN ARKANSAS-(Abstract Only)
    ANDERS, M.M., OLK, D.C., GRANTHAM, J., HOLZHAUER, J. SOIL AND PLANT NITROGEN CYCLING UNDER TILLAGE PRACTICES IN RICE-BASED ROTATIONS IN ARKANSAS. ASA-CSSA-SSSA PROCEEDINGS. 2003. CD-ROM. MADISON, WI. ASA-CSSA-SSSA.
    
  • QUANTITATIVE SOLID-STATE 13C NMR SPECTROSCOPY OF ORGANIC MATTER FRACTIONS IN LOWLAND RICE SOILS-(Peer Reviewed Journal)
    Smernik, R.J., Olk, D.C., Mahieu, N. 2004. Quantitative solid-state 13c NMR spectroscopy of organic matter fractions in lowland rice soils. European Journal of Soil Science. 55(2):367-379.
    
  • BEST MANAGEMENT PRACTICES RESEARCH IN A WATERSHED WITH SWINE PRODUCTION FACILITIES-(Other)
    TOMER, M.D., OLK, D.C. BEST MANAGEMENT PRACTICES RESEARCH IN A WATERSHED WITH SWINE PRODUCTION FACILITIES. NATIONAL PORK BOARD WEB SITE . 2003.
    
  • ORGANIC MATTER QUALITY, NITROGEN CYCLING AND YIELD TRENDS IN INTENSIVELY CROPPED PADDY SOILS-(Book / Chapter)
    
    
  • CHARACTERIZATION OF SOIL ORGANIC MATTER IN TROPICAL RICE SOILS BY ADVANCED SOLID-STATE NMR-(Abstract Only)
    SCHMIDT-ROHR, K., MAO, J., OLK, D.C. CHARACTERIZATION OF SOIL ORGANIC MATTER IN TROPICAL RICE SOILS BY ADVANCED SOLID-STATE NMR. AMERICAN CHEMICAL SOCIETY NATIONAL MEETING. 2003. PAPER NO. GEOC-058.
    
  • EXTRACTION OF HUMIC ACID FRACTIONS BASED ON BINDING TO SOIL POLYVALENT CATIONS.-(Abstract Only)
    OLK, D.C. EXTRACTION OF HUMIC ACID FRACTIONS BASED ON BINDING TO SOIL POLYVALENT CATIONS. AGRONOMY ABSTRACTS. 2002. CD-ROM. MADISON, WI.
    
  • ORGANIC FORMS OF SOIL NITROGEN-(Book / Chapter)
    Olk, D.C. 2008. Organic forms of soil nitrogen. In: Schepers, J.S., Raun, W.R., editors. Nitrogen in Agricultural Systems. Agronomy Monograph 49. ASA-CSSA-SSSA, Madison, WI. p. 57-100.
    
  • THE ROLE OF ORGANIC MATTER QUALITY IN NITROGEN CYCLING AND YIELD TRENDS IN INTENSIVELY CROPPED PADDY SOILS-(Proceedings)
    OLK, D.C., CASSMAN, K.G. ORGANIC MATTER QUALITY, NITROGEN CYCLING, AND YIELD TRENDS IN INTENSIVELY CROPPED PADDY SOILS. WORLD CONGRESS OF SOIL SCIENCE. 2002. CD-ROM. BANGKOK, THAILAND.
    
  • STRAW MANAGEMENT AFFECTING METHANE EMISSIONS FROM DIFFERENT RICE ECOSYSTEMS-(Proceedings)
    WASSMANN, R., BUENO, C.S., LANTIN, R.S., LU, W.F., CHAREONSILP, N., OLK, D.C. STRAW MANAGEMENT AFFECTING METHANE EMISSIONS FROM DIFFERENT RICE ECOSYSTEMS. WORLD CONGRESS OF SOIL SCIENCE. 2002. CD-ROM. BANGKOK, THAILAND.
    
  • ACCUMULATION OF LIGNIN RESIDUES IN ORGANIC MATTER FRACTIONS OF LOWLAND RICE SOILS: A PYROLYSIS-GC-MS STUDY-(Peer Reviewed Journal)
    OLK, D.C., DANCEL, M.C., MOSCOSO, E., JIMENEZ, R.R., DAYRIT, F.M. ACCUMULATION OF LIGNIN RESIDUES IN ORGANIC MATTER FRACTIONS OF LOWLAND RICE SOILS: A PYROLYSIS-GC-MS STUDY. S0IL SCIENCE. 2002. V. 167(9). P. 590-606.
    
  • SOIL PHENOLS CYCLING AND ORGANIC N AVAILABILITY DURING AN IRRIGATED RICE CROP-(Abstract Only)
    OLK, D.C., JIMENEZ, R.R., MOSCOSO, E. SOIL PHENOLS CYCLING AND ORGANIC N AVAILABILITY DURING AN IRRIGATED RICE CROP. AGRONOMY ABSTRACTS. 2001. CD-ROM. MADISON, WI. ASA-CSSA-SSSA.
    

• Projects

  Optimizing Carbon Management for Enhancing Soil and Crop Performances In-House Appropriated (D)   Accession Number:441097

  Mapping Subsoil Fragipan Breakdown by Ryegrass Cover Cropping Non-Assistance Cooperative Agreement (S)   Accession Number:442784

  Water and Light Use Efficiency of Native Grasses in a Silvopasture System Non-Assistance Cooperative Agreement (S)   Accession Number:443530

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