Soil electrical conductivity as a function of soil water content and implications for soil mapping

Abstract

Apparent soil electrical conductivity (EC a ) has shown promise as a soil survey tool in the Midwestern United States, with a share of this interest coming from the precision agriculture community. To fully utilize the potential of EC a to map soils, a better understanding of temporal changes in EC a is needed. Therefore, this study was undertaken to compare temporal changes in soil EC a between different soils, to investigate the influence of changes in soil water content on soil EC a , and to explore the impacts these EC a changes might have on soil mapping applications. To this end, a 90 m long transect was established. Soil EC a readings were taken in the vertical and horizontal dipoles at five points once every one to two weeks from June until October in 1999 and 2000. At the same time, soil samples were collected to a depth of 0.9 m for volumetric soil water content analysis. Soil EC a readings were compared to soil water content. At four of the five sites linear regression analysis yielded r 2 values of 0.70 or higher. Regression line slopes tended to be greater in lower landscape positions indicating greater EC a changes with a given change in soil water content. Two of the soils had an EC a relationship that changed as the soils became dry. This is an item of concern if EC a is to be used in soil mapping. Results indicated that soil water content has a strong influence on the EC a of these soils, and that EC a has its greatest potential to differentiate between soils when the soils are moist. Soil water content is an important variable to know when

Spatial Relation of Apparent Soil Electrical Conductivity with Crop Yields and Soil Properties at Different Topographic Positions in a Small Agricultural Watershed

“…In a no-till corn/soybean fields low ECa values were observed at higher elevation compared to high ECa values at low elevation [49]. Brevik et al [7] concluded that ECa may increase with an increase in volumetric water content due to strong relation (R 2 = 0.70) between them. They also observed that higher elevation soil sampling locations had lower ECa values compared to lower elevations due to higher volumetric water content at lower elevation positions.…”

“…The EMI technique can measure apparent soil electrical conductivity (ECa) by inducing an electrical current in the soil [7]. This method provides a relatively accurate, non-invasive, fast and inexpensive measurement of ECa [8][9][10].…”

“…The ECa is influenced by soil properties such as salinity, temperature, water content and bulk density [12]. Brevik et al [7] conducted a study on soils with different water content and found that ECa changes temporally and is highly dependent on soil moisture. Many studies have shown correlation of ECa with soil properties important for plant growth and crop yields including soil compaction, depth of claypan, soil water content, soil texture, drainage, TC, TN, soluble salts, extractable P and soil pH [3,[12][13][14].…”

The quest for understanding phenotypic variation via integrated approaches in the field environment

“…However, the ability to quantify the soil environment, including parameters like pH, organic matter, and moisture content, at high spatial resolution remains challenging given the heterogeneity of soils. Grid soil sampling and electromagnetic soil mapping, which measure soil conductivity to estimate properties like salinity, water content, and organic matter, have proven useful in characterizing spatial soil variability (Mallarino and Wittry, 2004;Brevik et al, 2006;Sun et al, 2013;Guo et al, 2015b). These methods are not without their limitations though; both grid soil sampling and electromagnetic mapping are typically performed once per season, making it impossible to capture the dynamic nature of the soil-water profile.…”

Precision agriculture applied to soybean crop: Part II – Temporal stability of management zones

“…However, such a relationship was not observed in the present study. Nonetheless, this behavior can be explained by the fact that ECa values are influenced by a combination of soil salts, mineralogy of the clay, and temperature of the soil (Brevik et al, 2006). Fig.…”