Location: Soil, Water & Air Resources Research
2023 Annual Report
Objectives
Objective 1: Develop improved crop practices based on carbon management that can be used to enhance soil physical properties in agricultural production systems, including better soil drainage and degradation of a subsoil fragipan.
Subobjective 1.A: Investigate decadal impacts of artificial drainage on soil health.
Subobjective 1.B: Evaluate annual ryegrass cover crops for improving seasonal soil water dynamics in fragipan soils.
Subobjective 1.C: Determine the chemical composition of fragipans at varying stages of degradation by ryegrass or humic product application.
Subobjective 1.D: Determine the effects of a humic product on the chemical speciation and quantities of root exudates released by ryegrass in a hydroponic system.
Objective 2: Establish the benefits of plant biostimulants, including humic products, to enhance plant growth and improve soil properties, and identify their mechanistic effects on plant physiological processes to develop more resilient agroecosystems.
Subobjective 2.A: Identify plant physiological processes that respond to humic product application for multiple plant types in diverse field settings and determine environmental influences on the plant responses.
Subobjective 2.B: Evaluate humic product impacts on soil physical properties.
Objective 3: Determine the responses of soil organic matter biochemistry to crop management practices in order to establish mechanistic interrelationships among soil carbon cycling, physical properties, and nutrient availability, and therefore develop improved management practices to optimize cropping system sustainability.
Approach
At multiple Corn Belt sites, historical changes in soil carbon (C) stocks and associated soil properties will be measured under current soil drainage practices, including proposed future practices, to help drainage management adapt to changing precipitation patterns in the Midwest. In the southern Corn Belt, existing studies of annual ryegrass and humic products as management options for degrading a hardened subsoil fragipan will be expanded. Their benefits will be measured for improving seasonal water relations and extending rooting depth through fragipan degradation at multiple sites. Existing field investigations of humic products as a crop amendment will be expanded by identifying their seasonal effects on plant carbohydrate production and plant hormone fluxes, as potential mechanistic explanations for the improved grain yield that was demonstrated previously in corn-soybean rotations. The commonality of these plant process responses to humic products will be established by expanding the scope of field sites to include natural grasslands, wheat, and potentially additional crops in other U.S. regions. To distinguish the relative contributions of plant vs. microbial materials to soil C sequestration, the concentrations of plant and microbial bio-marker compounds will be measured in labile fractions of soil organic matter for field treatments in two wheat-based and corn-based agroecosystems where soil C has been sequestered. Project results will provide critical information needed to guide the use of C amendments and other crop management practices for promoting soil C accumulation, enhancing other soil properties, and increasing crop performance, primarily for corn-based Midwestern cropping systems.
Progress Report
Objective 1. Daily soil moisture data from sensors imbedded in two farmers’ fields in southern Illinois were analyzed to determine seasonal soil water dynamics as influenced by the inclusion of annual rye grass within a corn-soybean rotation on two fragipan soils. A new brand of soil moisture sensors, that can be reused in field conditions, was calibrated and installed for this growing season, replacing the previously installed sensors that proved incompatible with removal and reinstallation before and after field operations. An initial set of soil cores collected from the two fragipan sites to a depth of 90 cm was analyzed for bulk density, texture, pH, total carbon (C) and nitrogen (N) concentrations, and available nutrient concentrations. Water retention characteristics of samples were determined using a pressure plate apparatus, and data were fitted to the Van Genuchten model. Two additional sets of cores were obtained from the same fragipan sites to enable detailed chemical and physical description of individual fragipan soil horizons and to begin a greenhouse study on rhizosphere effects of annual ryegrass roots on fragipan degradation. To determine the effect of humic acid application on crop residue decomposition and development of soil properties, corn stalk and root samples were collected, washed, air-dried, and weighed in nylon mesh bags. The mesh bags were buried within 2-5 cm depth of a humic product field experiment outside Ames, Iowa. Residue bags will be retrieved at regular intervals to determine mass loss and carbon and nitrogen concentrations.
Objective 2. Additional problems with an analysis for soluble leaf carbohydrates were resolved, enabling first-time detection of humic product benefits to leaf sugar production in field conditions. Positive results encouraged further measurement of plant photosynthesis as perhaps the primary plant response to humic product application. Specialized equipment for measuring soil penetrometer resistance at depth detected benefits of humic product application at depths down to 60 cm. Remote sensing by unmanned aerial vehicle continued for a humic product field trial. Multiple indices of remotely measured light absorption are being correlated with grain yield and leaf tissue nitrogen concentrations.
Objective 3. Further sets of California rice soils were analyzed for phenol concentrations, and the results strongly agreed with collaborators’ measurements of rice crop nitrogen uptake and grain yield, confirming earlier ARS work in Arkansas and the Philippines that soil phenol accumulation under anaerobic soil conditions inhibits late-season crop uptake of soil-derived nitrogen, impairing grain yield. Soil amino acids were analyzed for a collaboration with Iowa State University, demonstrating an effect of cropping system on extractable amino acids. A new stable isotope mass spectrometer was attached to an existing anion chromatograph, which will enable future studies of isotopically labeled crop residues as they transform into new soil organic matter and microbial communities.
Accomplishments
1. Rye cover crop benefits to young soil carbon pools and enzymes. Cover crops are planted after harvest of the main crop. During the off-season, their growth slows soil erosion and soil nutrient leakage into the environment. Evidence is inconsistent, though, whether their growth also increases total soil organic carbon levels. ARS scientists in Ames, Iowa, provided insights into this issue through study of young, more responsive pools of soil carbon in a nearby 20-year rye cover crop field trial under a corn-soybean rotation. Two physically extracted size classes of young soil organic matter increased in mass with cover cropping, while their biochemical composition remained plant-like. Whole soil and two chemically extracted fractions of soil carbon responded to cover cropping in their carbohydrate contents. All trends were clearer in the 0-5 cm depth than in the 5-15 cm depth for this no-tilled field. The trends were also clearer in a treatment pair where most corn biomass was harvested for silage production, compared to a second treatment pair having standard grain harvest and return of most corn silage to the soil. These results help identify cropping situations where rye cover cropping will more likely benefit soil properties. By contrast, soil enzymes increased greatly with rye cover cropping regardless of corn harvesting mode, indicating an independent benefit of cover cropping to soil microbial growth and nutrient cycling. These results demonstrate the complexity of rye cover crop effects on soil carbon cycling, which cannot be observed by measuring only total soil carbon. These results will be useful to land managers who practice cover cropping and to researchers of soil carbon cycling or cover cropping.
Review Publications
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.
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.
Chatterjee, A., Taylor, J.M., Moore, M.T., Locke, M.A., Hoeksema, J.D. 2023. Shallow water habitat management influences soil CO2 efflux from agricultural fields in the Lower Mississippi River Basin (LMRB), USA. Agrosystems, Geosciences & Environment. 211–224 (2019). https://doi.org/10.1002/agg2.20365.
Chatterjee, A., Anapalli, S.S. 2022. Comparing eddy covariance-based cotton evapotranspiration with CSM-CROPGRO and APSIM-OzCot simulations in Mississippi. Water. 14(24):4022. https://doi.org/10.3390/w14244022.
Harvey, L.M., Shankle, M.W., Morris, C.J., Hall, M.A., Chatterjee, A., Harvey, K.M. 2022. Sweetpotato (Ipomoea batatas L.) response to incremental application rates of potassium fertilizer in Mississippi. Horticulturae. 8(9). https://doi.org/10.3390/horticulturae8090831.
