Landscape scale assessment of soil processes and pedochemical tracers across watersheds.

Much of the soil changes across landscapes can be linked to water because water provides the energy for chemical and physical weathering. The Southern Indiana Purdue Agriculture Center was selected to analyze variability and soil characteristics within a pastured watershed. A total of 8 soils at different landscape positions has been sampled and analyzed for physical and chemical properties including trace elements. The data will be summarized and used initially to develop relationships between hydrologic characteristics related to soil properties for development of quantitative relationships between soils and hydrology. The next phase of the research will utilize intense watershed sampling to develop soil variability models and quantify variability using geostatistical models that can ultimately link high intensity soil attribute data to moderately intense soil survey map by providing a basic understanding of soil processes that lead to a continuum soil differences. The goal for developing these soil models will be to elucidate basic information regarding soil formation to provide more detailed information for incorporation into applications such as precision farming, nutrient management plans, and hydrological and ecological models. Collaborators: USDA-NRCS Soil Survey Program

Developing soil attribute maps using soil landscape interface models.

A digital soil survey update map for Howard County, Indiana, is being made using relationships between terrain attributes and soil properties. A soil land inference model using fuzzy logic provides the mechanism whereby terrain/soil relationships are extended from areas of direct soil property observation to areas of terrain analysis alone. Knowledge mining from existing soil survey data supplements the work and helps to establish terrain-soil relationships. It has been generally assumed that terrain attributes lose relevance and utility with decreasing landscape relief, but this is not the case in this fairly flat landscape. The Topographical Wetness Index (TWI) shows a strong utility in distinguishing Mollisols from Alfisols in the county. Altitude above Channel Network is useful for distinguishing soils neighboring major drainage networks. The newly updated soil survey will provide point numerical estimates with statistical probabilities for soil properties rather than numerical ranges of soil attributes provided in current polygon-based survey product. This product and development will provide more useful data and information for the agricultural and non-agricultural users by providing data layers of common soil properties that are linked to but not based on soil taxonomy. Collaborators: USDA-NRCS Soil Survey Program

Spatial variability of potassium plant availability with depth in a Southeastern Indiana drainage toposequence.

This research is a collaborative study with Dr. Brad Joern. The availability to plants of potassium in soils is influenced by many factors including the composition and degree of weathering of initial soil parent material, fertilizer applications, fixation potential, removal of K by cropping, historical seasonal fluctuations of soil moisture, pH, and temperature. Examination of these factors from the standpoint of soil spatial variability at the field scale related to potassium variability could reveal useful trends relevant to K management. The proposed investigation utilizes an intense grid sampling scheme and geostatistical methods to provide an estimate of the required sampling density for full characterization of K (in various forms) and other extractable nutrients. These data will be related to soil properties at the field scale in key Alfisols developed in loess over Illinoisan glacial till in southeastern Indiana. The trends in K availability and concentration will be developed based on soil properties and key landscape attributes. From preliminary data, grid sampling strategies inclusive of slope components and landscape features can better characterize soil variability than grid sampling strategies that do not include such features. The research will lead to better sampling strategies potassium which will lead to better fertilization management plans. Collaborators: Drs. Brad Joern, Brad Lee and Jim Camberato

Evaluation of Soil Carbonate Weathering Rates Related to Water Dynamics on Calcareous Till Moraine in NE Indiana.

The Wabash Moraine is one of several concentric end moraines in northeastern Indiana. Soils there are developed in dense calcareous glacial till and are high in illitic clay. Spatial variability of soil properties was examined on a 3.5 ha field on the Moraine in a 20 m grid-sampling scheme. Examined properties included texture, chemical properties, depth of soil development, bulk density, depth to platy structure, elevation, and slope. Soil properties exhibited predictable patterns based on landscape position, elevation, and slope. Soil development was deeper in areas experiencing greater water energy influx due to slope position and was evident by depth to presumably plant-induced heightened acidity, depth to unweathered glacial till (characterized by massive or platy texture), and depth to high-level calcium carbonates (which are leached from the soil horizon with weathering through time). Results indicate that slope and landscape position can be valuable compliments to a grid sampling strategy and that strong correlations exist between slope/landscape positions and observed soil properties. Grid sampling strategies that include a slope/landscape position component should be more reliable as descriptive tools of soil variability than grid sampling approaches that do not include slope/landscape position values. This study revealed that lower landscape positions weather carbonate at rates 4 times greater than summit positions which will provide better accounting for inorganic C components in the terrestrial C cycle. Further investigations are planned to relate water dynamics to rates of carbonate weathering. Collaborators: USDA-NRCS Soil Survey Program

Evaluation of opal phytoliths as a marker to estimate oxidation and subsidence in Histosols of Northern Indiana.

During settlement of Indiana, many wetlands containing Histosols were drained to utilize land for agriculture and habitation. There are two major issues with drainage of Histosols. Soil subsidence due to degradation of organic matter alters the landscape be decreasing the gradient of surface elevations to drainage ditch depth. This could lead to further dredging and increased cost to agriculture producers. Another issue that affects the global community is the evolution of CO2 from degrading organic matter in Histosols. This study utilizes biogenic opal left from decaying plants as markers of past climates and rates of accumulation and/or subsidence. In this study, four sites were located and drained-undrained phases of Histosols were sampled. The biogenic opals were separated from each soil by depth to reconstruct subsidence rates and past climates. In the drained Histosols, there was a concentration of biogenic opal in surface horizons due to deflation and organic matter decomposition. These data will be coupled with physical properties and reconstruction analysis to predict soil depth prior to drainage. This information will be used for CO2 evolution estimates from organic soils, tile ditching management, and soil subsidence estimates.  Collaborators: USDA-NRCS Soil Survey Program

Impacts of tile drainage on water table dynamics on the Cobbs Fork-Avonburg catena in SE Indiana.

Tile drainage on Indiana landscapes is necessary for current agriculture practices but has altered subsurface soil hydrology. This study uses high frequency monitoring to determine drainage response times, distance from tile that water tables are affected and relationship to reduction-oxidation processes necessary to form redoximorphic features. The site is located at SEPAC in southern Indiana and will provide supplemental information for an ongoing tile drainage study conducted by Dr. Eileen Kladivko. The focus of the National Cooperative Soil Survey is shifting from producing static printed soil survey reports to providing a dynamic resource of soils information for a wide range of needs. As information is gathered, it is directly entered into a database that allows constant updates for improved estimates of soil properties. The National Soil Information System (NASIS) is the core component of this vision and is designed to manage and maintain soil data from collection to dissemination. Once information is gathered and analyzed at SEPAC, the hydrologic information will be updated in NASIS for these soils which will provide soil hydrologic estimates for millions of acres in Indiana and surrounding states. These data will be useful for quantifying landscape drainage and nutrient loading into streams from tile drains. Collaborator: Dr. Eileen Kladivko