|BROWN, MEGHAN - U.S. ARMY CORP OF ENGINEERS (USACE)|
|HEINSE, REPORT - UNIVERSITY OF IDAHO|
|JOHNSON-MAYNARD, J - UNIVERSITY OF IDAHO|
Submitted to: Vadose Zone Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/27/2020
Publication Date: 1/15/2021
Citation: Brown, M., Heinse, R., Johnson-Maynard, J., Huggins, D.R. 2021. Time-lapse mapping of crop and tillage interactions with soil water using electromagnetic induction. Vadose Zone Journal. 20(4). Article e20097. https://doi.org/10.1002/vzj2.20097.
Interpretive Summary: Quantifying field variations of soil water are critical to many decisions in agriculture. In dryland crop production, farmers often use crop rotation and tillage practices to strategically manage soil water to benefit cash crops. We used rapidly obtained measurements of apparent electrical conductivity (ECa) to seasonally assess soil crop (winter wheat, spring pea and spring barley) and tillage (no-tillage and chisel plow) impacts on soil water in the Palouse region of Northern Idaho. Weekly measurements of ECa were converted to soil water using additional variables of growing degree days, elevation, soil clay and silt content. Results showed crops had the greatest impact on soil water with spring pea using less water than spring barley while winter wheat used the most. Soil ECa tended to be greater in no-tillage, but was not significantly different to chisel plow treatments. ECa maps showed consistent field patterns driven primarily by crop type that were evident even in uncalibrated imagery. These results will be useful for farmers, NRCS and scientists interested in assessing crop and tillage effects on field variations of soil water.
Technical Abstract: Assessing spatio-temporal variations in soil water is critical to many decisions in precision agriculture. In dryland crop production regions, farmers often use crop rotation and tillage practices to strategically store soil water to benefit cash crop production. Significant knowledge gaps exist, however, in linking site-specific water storage and crop use to topography, soil properties and agronomic practices. We used time-lapse electromagnetic induction to measure apparent electrical conductivity (ECa) and inferred spatio-temporal variability of soil water comparing crop (winter wheat, spring peas and spring barley) and tillage (no-tillage and chisel plow) impacts using a split-plot design in the Palouse region of Northern Idaho. Weekly measurements of ECa were converted to soil water content using multiple linear regression with the help of principal component analysis. Separating factors of temporal stability and variability allowed us to derive crop-specific calibrated relationships between soil water content and additional variables of growing degree days, elevation, clay content, and silt content. Results show that spring pea retained the highest water content, followed by spring barley and winter wheat. ECa maps showed highly structured and consistent patterns driven primarily by crop type that were evident even in uncalibrated imagery. While soil ECa tended to be greater in no-tillage as compared to chisel plow treatments, no significant differences in soil water content occurred. This may be partially due to the limited number of years of no-till practice at this site.