CHARACTERIZING FIELD-SCALE SOIL VARIABILITY ACROSS THE MIDWEST WITH SOIL ELECTRICAL CONDUCTIVITY

Authors: Sudduth, Kenneth - Ken; Kitchen, Newell; BATCHELOR, W - IA STATE U; BOLLERO, G - U OF IL; BULLOCK, D - U OF IL; CLAY, D - SD STATE U; PALM, H - U OF MO; WIEBOLD, W - U OF MO; PIERCE, F - WA STATE U; SCHULER, R - U OF WI

Submitted to: International Conference on Precision Agriculture Abstracts & Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 7/17/2002
Publication Date: 12/1/2002
Citation: SUDDUTH, K.A., KITCHEN, N.R., BATCHELOR, W.D., BOLLERO, G.A., BULLOCK, D.G., CLAY, D.E., PALM, H.L., WIEBOLD, W.J., PIERCE, F.J., SCHULER, R.T. CHARACTERIZING FIELD-SCALE SOIL VARIABILITY ACROSS THE MIDWEST WITH SOIL ELECTRICAL CONDUCTIVITY. PROCEEDINGS 6TH INTERNATIONAL CONFERENCE ON PRECISION AGRICULTURE. CD-ROM (UNPAGINATED). AMERICAN SOCIETY OF AGRONOMY, MADISON, WI. 2002.

Interpretive Summary: Soil apparent electrical conductivity (EC) is influenced by a number of factors, including soil moisture, clay content, and salinity. Because of this, spatial measurements of conductivity can, when properly calibrated, provide indicators of a number of soil parameters important in site-specific crop management, or precision agriculture. Two types of EC sensors usable in precision agriculture are commercially available. The Geonics EM38 is a non-contact sensor which measures EC to a depth of approximately 1.5 m through the principle of electromagnetic induction. The Veris 3100, a newer product, uses coulters in contact with the soil to provide two simultaneous EC measurements to depths of approximately 0.3 m and 1.0 m. We obtained EC measurements in crop production fields in six Midwestern states using both these instruments and found that they gave similar but not identical results. Differences between the sensors were greater on fields with more layered soils, such as the Missouri claypan soil fields. The two soil properties most strongly related to EC were clay content and cation exchange capacity (CEC). The results of this research will benefit users of EC instruments, giving them a better understanding of the advantages and limitations of each type. The results will also benefit scientists and extension personnel, who may need to understand the differences between the instruments for research or demonstration purposes.

Technical Abstract: Apparent profile soil electrical conductivity (ECa) can be an indirect indicator of a number of soil physical and chemical properties. Commercially available ECa sensors can be used to efficiently and inexpensively develop the spatially dense datasets desirable for describing within-field spatial soil variability in precision agriculture. The objective of this research was to compare ECa measurements from a non-contact, electromagnetic induction-based sensor (Geonics EM38) to those obtained with a coulter-based sensor (Veris 3100) and to relate ECa data to soil physical properties. Data were collected on twelve fields in six states of the north-central US. At 12 to 20 sampling sites in each field, 120 cm deep soil cores were obtained and used for soil property determination. Within a single field and measurement date, EM38 data and Veris deep (0-100 cm depth) data were most highly correlated. Differences between ECa sensors were more pronounced on more layered soils, such as the claypan soils of the Missouri fields, due to differences in depth-weighted sensor response curves. Correlations of ECa with clay content and CEC were generally highest and most persistent across all fields and ECa data types. It may be possible to develop relationships between ECa and clay and CEC that are applicable across a wide range of soil and climatic conditions, such as were found in the study fields. Overall, data obtained with both types of ECa sensors were similar and exhibited similar relationships to soil physical and chemical properties.