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Investigation of Soil Moisture Variability Under Sod in East-Central Illinois
Scott, R.W., E.C.Krug, S.L.Burch, C.R.Mitsdarfer, P.Nelson
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https://hdl.handle.net/2142/42679
Description
- Title
- Investigation of Soil Moisture Variability Under Sod in East-Central Illinois
- Author(s)
- Scott, R.W., E.C.Krug, S.L.Burch, C.R.Mitsdarfer, P.Nelson
- Issue Date
- 2010-07
- Keyword(s)
- Soil moisture
- Abstract
- Long-term data collection of volumetric soil moisture under sod has been conducted in Illinois
for more than 25 years. These data have been used in numerous applied and modeling studies in
which the results are often related to regional conditions under a variety of surface covers. The
actual level of representation of these data to nearby areas with different surface covers,
however, is unknown. In 2006–2007, the Soil Moisture Under Sod Experiment was conducted at
Bondville, Illinois to increase understanding of soil moisture variability across a very small area
of seemingly uniform surface and near-surface conditions. Ten locations were chosen at random
within a 5.9-hectare sodded field for twice-weekly neutron probe soil moisture observations over
a period of more than 13 months. Measurements were taken at the surface and at 20-centimeter
intervals down to 2 meters, precisely matching the historic Illinois depth observations. A detailed
surface terrain analysis was conducted to consider impacts of surface slope or ponding potential
on soil moisture attributes at each monitoring location across the very low-relief surface. The
near-surface water table level at the field location was monitored. At the end of observations, soil
property heterogeneity (e.g., soil porosity, bulk density, and soil color) was determined by
digging trenches and extracting soil cores immediately adjacent to each monitoring site at all
observation levels within the predominantly loess soil.
Results indicate a strong temporal consistency at each site in trends of volumetric soil moisture at all depths throughout the experiment. However, inter-site spatial variability increased with depth, indicated by an average standard deviation of all temporal observations of 2.26% in the top 30 centimeters of soil and 5.19% in the 170- to 200-centimeter layer. Differences between the average field soil moisture at all primary randomly selected sites and the historic Bondville site was 2.39% and 6.51%, respectively. Variations in soil moisture in the lowest layers appear to be related to an intrusion of the water table. In addition, an apparent relationship was observed between soil moisture in deeper layers and surface terrain slope, and to a lesser extent with soil porosity and bulk density. Further, the near-surface soil moisture observations under sod in loess soils over one small region in Illinois are useful as ground truth for near-surface data observed with remote-sensing observations.
The question of representativeness of soil moisture under sod to moisture under crop surface covers was addressed in a cursory manner. Differences similar in magnitude to those found under sod were observed. Soil moisture variability measured across this seemingly uniform field suggests that proper use of the historic Illinois dataset by future researchers related to adjacent areas may need greater attention. Most of Illinois is under an agricultural cover, not sod, as are the surface covers at all of Illinois’ soil moisture monitoring sites. Adequate data monitoring of terrain slope, soil profiles, and water table climatology under various major surface covers within a region is recommended prior to installing new soil moisture monitoring sites and before making useful assumptions concerning spatial representation that attribute individual soil moisture datasets to adjacent areas.
- Publisher
- Illinois State Water Survey
- Series/Report Name or Number
- Report of Investigation (Illinois State Water Survey) RI-119
- Type of Resource
- text
- Language
- en
- Permalink
- http://hdl.handle.net/2142/42679
- Copyright and License Information
- This document is a product of the Illinois State Water Survey, and has been selected and made available by the Illinois State Water Survey and the University Library, University of Illinois at Urbana-Champaign. It is intended research and educational use, and proper attribution is requested.