Soil change across Iowa - From the land to the lab to the map
Date
2023-12
Authors
Bentancor, Luis
Major Professor
Advisor
Miller, Bradley A
Burras, Charles L
Cruse, Richard
Gleder, Brian
O'Brien, Peter
Committee Member
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Abstract
Despite the substantial effect of how and why management practices affect the rates of soil change over time, and what methods should be chosen to assess those changes, our understanding of it is still limited. This study aims to 1) compare which is the best method to capture soil organic carbon (SOC) changes accurately and cost-effectively. 2) assessed how the mollic epipedon thickness changed in Iowa in the last 70 years using digital soil mapping (DSM) techniques and soil legacy data. 3) study the impacts of pipeline on dynamic soil properties six years after installation.
For (1) I found that the presence of inorganic carbon (IC) had a negative impact on the relationship between Dry Combustion (DC) and Loss on Ignition (LOI) measurements. Conversion factors (CF) varied depending on treatment, physiographic region, and soil horizon, but the average CF across all LOI treatments exceeded 2.0, confirming that the conventional CF of 1.724 is too low. Furthermore, the research showed that soil organic carbon (SOC) estimation using a chroma meter and smartphone-based digital images are accurate but lacks precision. In particular, LOI conducted at 400 °C for 16 hours demonstrated medium to high accuracy and high replicability. It also proved to be a cost-effective alternative, being 92% cheaper than DC, making it a suitable method for carbon credits certification.
For (2) the findings showed that soil loss is not a continuous, steady process; instead, it's influenced by land-use changes, tillage intensity, and increasing rainfall erosivity over time. For (3) the results indicated that the impacts of pipeline on dynamic soil properties six years after installation showed that physical properties, especially bulk density, and as a consequence, total porosity and available water for plants were the most affected. The reduction in available water for plants produces yield reductions between 12 and 22%.
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dissertation