Location: Soil, Water & Air Resources Research
2019 Annual Report
Objectives
Objective 1: Assess humic products and cover crops as management options for promoting soil carbon pools, nutrient cycling for crop growth, and increased yield.
Objective 2: Assess the effectiveness of grass buffers, blind inlets, and carbon-based reactive barriers in the form of filter socks for phosphorus management.
Objective 3: Quantitatively characterize soil health and crop productivity responses to carbon input from crop sequences and carbon losses from tillage, crop residue management and harvest.
Approach
To enhance management of soil carbon, laboratory analyses for specific carbohydrates, amino compounds, phenols, and fatty acids will be used to distinguish between labile and recalcitrant fractions of soil organic matter (SOM). Effects of applying humic products and cover crops on short- (e.g., nutrient cycling and soil structure) and long-term (e.g., carbon sequestration) soil changes will be determined. Humic product application will be evaluated as a mitigation strategy for SOM loss due to excessive crop residue removal for bioenergy production. Filter socks filled with wood chips and bark will be evaluated as a means to efficiently catch dissolved and sediment-bound phosphorus moving with runoff water into surface inlets, subsurface drainage systems, and ultimately natural water bodies. Process-level knowledge from laboratory and plot-scale research will enhance development of site-specific subfield management strategies for increasing producer profitability and providing sustainable feedstock supplies at field and landscape scales. Several different crop rotations utilizing corn, soybean, alfalfa, wheat, rye, field pea, and tillage radish will be evaluated with various levels of stover harvest. No-tillage, strip-tillage, and chisel-plow management as well as effects of biochar will be determined. Effects on nutrient cycling, soil carbon stocks, and soil health (using the Soil Management Assessment Framework) will be quantified. Project results will provide critical information needed to elucidate the effects of crop residue management and carbon-based amendments on soil physical and biochemical properties, economic returns, and long-term sustainability of corn-based Midwestern cropping systems.
Progress Report
Objective 1: Humic product application for 4 to 5 years had only modest benefits on the amounts of young soil humic fractions. Their biochemical compositions are still being assessed for responsiveness to humic product application. By contrast, humic product application was found in one field to slightly improve soil physical properties, despite abundant background levels of soil carbon. Slight benefits were observed for soil penetration resistance, water-holding capacity, and bulk density, which were better expressed in subsoil depths than in the surface depth. Effects of cover cropping for more than 20 years on soil humic fraction amounts were observed, which also responded to different crop residue managements within the cover crop treatments. Data sets from numerous humic product field experiments were finalized and statistically analyzed to support the preparation of peer-reviewed manuscripts.
Objective 2: The scientist was retired through FY 2019, and this position has since remained vacant.
Objective 3: The scientist retired five months into FY 2019, and this position has since remained vacant.
Accomplishments
1. The pivotal roles of soil organic matter (SOM) in agricultural soils can be accurately studied through alkaline extraction for humic fractions. Pivotal roles of soil organic matter (SOM) in soil processes have long been studied by fractionating SOM into pure organic pools that are more amenable to chemical analyses. The classical fractionation approach, solubilization in alkaline solutions to extract humic fractions, has recently become increasingly criticized as unfit for research because it allegedly produces new compounds that are not found in natural soils. In response to calls to ban publication of research involving alkaline extractions of SOM, the editor of the Journal of Environmental Quality (JEQ) invited ARS researchers in Ames, Iowa, to lead in publishing reviews that summarize practical applications of humic fractions for resolving multiple agricultural and environmental issues in soils and natural water bodies. The first review also provided evidence for only limited chemical alteration of SOM during alkaline extraction. Within five months of its publication, this review has been downloaded 3.5 times the average lifetime number of downloads for JEQ articles. A link to this review has been posted on the website of the International Humic Substances Society as a potential citation to support future manuscripts using alkaline extractions. The JEQ has since called for a special issue on alkaline extraction studies.
Review Publications
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.
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.
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.
Karlen, D.L., Obrycki, J.F. 2018. An Iowa on-farm carbon and soil health indicator assessment study. Agronomy Journal. https://doi.org/10.2134/agronj2018.02.0113.
Karlen, D.L., Schmer, M.R., Kaffka, S.R., Clay, D.E., Wang, M.Q., Horwath, W.R., Kendall, A.M., Keller, A., Pieper, B., Unnasch, S., Darlington, T., Vocasek, F., Chute, A.G. 2018. Unraveling crop residue harvest effects on soil organic carbon. Agronomy Journal. 111:93-98. https://doi.org/10.2134/agronj2018.03.0207.
Obrycki, J., Karlen, D.L. 2018. Optimizing Iowa land use: Past perspectives for current questions. Journal of Soil and Water Conservation. 73(6):693-704. https://doi.org/10.2489/jswc.73.6.693.
Obrycki, J.F., Karlen, D.L., Cambardella, C.A., Kovar, J.L., Birrell, S.J. 2018. Corn stover harvest, tillage, and cover crop effects on soil health indicators. Soil Science Society of America Journal. 82(4):910-918. https://doi.org/10.2136/sssaj2017.12.0415.
Obrycki, J.F., Kovar, J.L., Karlen, D.L. 2018. Subsoil potassium in central Iowa soils: Status and future challenges. Agrosystems, Geosciences & Environment. https://doi.org/10.2134/age2018.07.0018.
Obrycki, J.F., Kovar, J.L., Karlen, D.L., Birrell, S.J. 2018. Ten-year assessment encourages no-till for corn grain and stover harvest. Agricultural and Environmental Letters. 3:1800034. https://doi.org/10.2134/ael2018.06.0034.
Mendes, L.C., Tormena, C.A., Cherubin, M.R., Karlen, D.L. 2018. Soil health assessment and maintenance in Central and South Central Brazil. In: Reicosky, D, editor. Managing Soil Health for Sustainable Agriculture. Cambridge, UK:Burleigh Dodds Science Publishing. p. 379-415.
Dale, V.H., Kline, K.L., Richard, T.L., Karlen, D.L., Belden, W.W. 2018. Bridging biofuel sustainability indicators and ecosystem services through stakeholder engagement. Biomass and Bioenergy. 114:143-156. https://doi.org/10.1016/j.biombioe.2017.09.016.
Malone, R.W., Herbstritt, S., Ma, L., Richard, T., Cibin, R., Gassman, P., Zhang, H., Karlen, D.L., Hatfield, J.L., Obrycki, J., Helmers, M., Jaynes, D.B., Kaspar, T.C., Parkin, T.B. 2019. Corn stover harvest and N losses in central Iowa. Science of the Total Environment. 663:776-792. https://doi.org/10.1016/j.scitotenv.2019.01.328.
Xu, H., Sieverding, H., Kwon, H., Clay, D., Stewart, C.E., Johnson, J.M., Qin, Z., Karlen, D.L., Wang, M. 2019. A global meta-analysis of soil organic carbon response to corn stover removal. Global Change Biology Bioenergy. 00:1-19. https://doi.org/10.1111/gcbb.12631.
Delgado, J.A., Vandenberg, B.C., Kaplan, N.E., Neer, D.L., Wilson, G.J., D Adamo, R.E., Carter, J.D., Ogan, L., Grow, N.O., Marquez, R.D., Arthur, D.K., Eve, M.D., Del Grosso, S.J., Johnson, J.M., Karlen, D.L., Durso, L.M., Finley, J.W., Acosta Martinez, V., Harmel, R.D., Derner, J.D. 2018. Agricultural Collaborative Research Outcomes System: AgCROS - An emerging network of networks for national food and environmental security and human health. Journal of Soil and Water Conservation. 73(6):158A-164A. https://doi.org/10.2489/jswc.73.6.158A.
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.
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.
