More Like this

1. Erodibility of Claypan Soils in Southeastern Kansas

   Mathis, Mark; Kulesza, Stacey; Sassenrath, Gretchen (November 2017, Kansas Governor's Water Conference)

   The objective of this research is to determine the fundamental mechanisms that cause loss of topsoil. Claypan soils cover approximately 10 million acres in the United States and are characterized by a highly impermeable layer below the topsoil. This impermeable layer acts as a barrier for infiltrating water which may be increasing the erosion rate and sediment transport of upper soil layers. This increasing topsoil depletion ultimately limits the productive capacity of agronomic fields. This study focuses on the undermining of the topsoil due to the impermeable claypan layer in Southeastern Kansas where the topsoil depth is limited and, in places, the claypan layer is exposed at the surface. Using LiDAR-derived digital elevation maps, the potential areas of critical soil loss and hydrologic flow patterns is determined. Surface soil apparent electrical conductivity (EC) measurements highlight the soil variability throughout the field. Electrical Resistivity Tomography (ERT) surveys is also performed to determine the depth to the claypan layer in low and high crop yield areas. The results indicate that the areas of high EC correlated with high clay content and low crop yield, while areas of low EC correlated with high crop yield. The results also indicate that the claypan layer in the low crop yield area is 1.0 m thick and significantly thins once reaching the high crop yield area. The next phase of this ongoing research is to measure the soil properties between the low and high crop yield areas, measure the movement of water at the claypan interface, and measure sediment transport at the claypan interface. 

   more » « less
2. Electrical Resistivity Tomography of Claypan Soils in Southeastern Kansas

   https://doi.org/https://doi.org/10.4148/ 2378-5977.7574  

   Mathis, M. A.; Tucker-Kulesza, S. E.; and Sassenrath, G. F. (March 2018, Kansas Agricultural Experiment Station Research Reports)

   Claypan soils cover approximately 10 million acres across several states in the central United States. The soils are characterized by a highly impermeable clay layer within the profile that impedes water flow and root growth. While some claypan soils can be productive, they must be carefully managed to avoid reductions to crop productivity due to root restrictions, water, and nutrient limitations. Clay soils are usually resistant to erosion but may exacerbate erosion of the silt-loam topsoil. Soil production potential is the capacity of soil to produce at a given level (yield per acre). The productive capacity is tied to soil characteristics, which can be highly variable within a field. In this project, we have used imagery analysis to study the aerial images and terrain of fields during different productive times of the year to identify where soil samples should be collected for more discrete analysis. Soil samples provide valuable information; however, the amount of data obtained from a relatively small area within a field does not provide sufficient information to delineate the subsurface characteristics. To address the limitations of sampling, we have also employed the use of yield maps collected from commercial yield monitors on production-scale combines and surface electrical conductivity measurements (Sassenrath and Kulesza, 2017). Soil conductivity is a measurement of how well a representative volume of soil conducts electricity. Soil conductivity is a function of the soil clay content, moisture content, and other measurable soil properties (Kitchen et al., 2003); as such, it has become a valuable tool for mapping in-field variability. The main advantage of a soil conductivity measurement is that the entire surface of a field can be imaged. The disadvantage of a soil conductivity measurement is that data are only collected near the surface (10 – 30 inches) and the measurements are relative measurements. This means that the conductivity mappers can identify changes in soil properties, but they cannot directly tell researchers what caused these changes. Electrical resistivity tomography (ERT) is a popular near-surface geophysical measurement for geophysical and engineering applications. The term “near-surface” generally means down to around 30 feet in the subsurface. Electrical resistivity is the reciprocal measurement of electrical conductivity; therefore, both systems measure differences in the same soil properties. ERT measurements are different than surface electrical conductivity measurements because ERT collects a “slice” of data into the subsurface, as opposed to only changes at the surface area. Relative measurements, similar to those collected in an electrical conductivity survey, are collected; however, in ERT studies the data are mathematically inverted to yield the true electrical resistivity of the soil with depth. This allows an interpretation of the changing soil properties with depth to reduce the required amount of sampling. A disadvantage of an ERT survey is that the data acquisition is stationary so mapping an entire field is not feasible. We have used a coupled process of imagery and terrain analysis, yield maps, and electrical conductivity measurements to guide the locations of ERT surveys in this project (Tucker-Kulesza et al. 2017). 

   more » « less
3. The extent of soil loss across the US Corn Belt

   https://doi.org/10.1073/pnas.1922375118  

   Thaler, Evan A.; Larsen, Isaac J.; Yu, Qian (February 2021, Proceedings of the National Academy of Sciences)

   Soil erosion in agricultural landscapes reduces crop yields, leads to loss of ecosystem services, and influences the global carbon cycle. Despite decades of soil erosion research, the magnitude of historical soil loss remains poorly quantified across large agricultural regions because preagricultural soil data are rare, and it is challenging to extrapolate local-scale erosion observations across time and space. Here we focus on the Corn Belt of the midwestern United States and use a remote-sensing method to map areas in agricultural fields that have no remaining organic carbon-rich A-horizon. We use satellite and LiDAR data to develop a relationship between A-horizon loss and topographic curvature and then use topographic data to scale-up soil loss predictions across 3.9 × 10⁵km²of the Corn Belt. Our results indicate that 35 ± 11% of the cultivated area has lost A-horizon soil and that prior estimates of soil degradation from soil survey-based methods have significantly underestimated A-horizon soil loss. Convex hilltops throughout the region are often completely denuded of A-horizon soil. The association between soil loss and convex topography indicates that tillage-induced erosion is an important driver of soil loss, yet tillage erosion is not simulated in models used to assess nationwide soil loss trends in the United States. We estimate that A-horizon loss decreases crop yields by 6 ± 2%, causing $2.8 ± $0.9 billion in annual economic losses. Regionally, we estimate 1.4 ± 0.5 Pg of carbon have been removed from hillslopes by erosion of the A-horizon, much of which likely remains buried in depositional areas within the fields. 

   more » « less
4. Soil physical and chemical properties of gypsum & non-gypsum soils from the Chihuahuan and Mojave Deserts in 2023

   https://doi.org/10.6073/pasta/01123dd2785f8ff3cb314a837d3bb6fd  

   Gobbie, Katelyn G; Pietrasiak, Nicole; Drenovsky, Rebecca E (January 2024, Environmental Data Initiative)

   This dataset contains data for soil physical and chemical properties of gypsum and non-gypsum soils in the northern Chihuahuan and eastern Mojave Deserts. Data were obtained from 20 study sites total, 10 located on soils derived from gypsum parent material and 10 located on soils derived from non-gypsum parent materials. Sites were grouped into 10 pairs, in which every gypsum site was partnered with a non-gypsum site located in the same region. Apart from soil type, partnered-site characteristics (topography, climate, elevation, slope, aspect, and presence of biocrusts) were held relatively constant. Site info and characteristics data can be accessed at knb-lter-jrn.210616001. Soil physical properties included: percent gravel, percent < 2mm fraction, soil aggregate stability, and soil compaction. Soil chemical properties were: percent gypsum content, pH, EC, and soil soluble concentrations of calcium, magnesium, potassium, sulfur, and phosphorus. The resulting soil data was used to understand physical and chemical differences between gypsum and non-gypsum soils and to examine how biocrust community types and moss species abundance and composition were associated with the measured soil variables. This study and dataset are complete. 

   more » « less
5. Seagrass Abundance Predicts Surficial Soil Organic Carbon Stocks Across the Range of Thalassia testudinum in the Western North Atlantic

   https://doi.org/10.1007/s12237-023-01210-0  

   Fourqurean, James W.; Campbell, Justin E.; Rhoades, O. Kennedy; Munson, Calvin J.; Krause, Johannes R.; Altieri, Andrew H.; Douglass, James G.; Heck, Kenneth L.; Paul, Valerie J.; Armitage, Anna R.; et al (May 2023, Estuaries and Coasts)

   The organic carbon (Corg) stored in seagrass meadows is globally significant and could be relevant in strategies to mitigate increasing CO2 concentration in the atmosphere. Most of that stored Corg is in the soils that underlie the seagrasses. We explored how seagrass and soil characteristics vary among seagrass meadows across the geographic range of turtlegrass (Thalassia testudinum) with a goal of illuminating the processes controlling soil organic carbon (Corg) storage spanning 23° of latitude. Seagrass abundance (percent cover, biomass, and canopy height) varied by over an order of magnitude across sites, and we found high variability in soil characteristics, with Corg ranging from 0.08 to 12.59% dry weight. Seagrass abundance was a good predictor of the Corg stocks in surficial soils, and the relative importance of seagrass-derived soil Corg increased as abundance increased. These relationships suggest that first-order estimates of surficial soil Corg stocks can be made by measuring seagrass abundance and applying a linear transfer function. The relative availability of the nutrients N and P to support plant growth was also correlated with soil Corg stocks. Stocks were lower at N-limited sites than at P-limited ones, but the importance of seagrass-derived organic matter to soil Corg stocks was not a function of nutrient limitation status. This finding seemed at odds with our observation that labile standard substrates decomposed more slowly at N-limited than at P-limited sites, since even though decomposition rates were 55% lower at N-limited sites, less Corg was accumulating in the soils. The dependence of Corg stocks and decomposition rates on nutrient availability suggests that eutrophication is likely to exert a strong influence on carbon storage in seagrass meadows. 

   more » « less