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United States Department of Agriculture

Agricultural Research Service

Title: Repeatability of Soil Apparent Electrical Conductivity Measured by the Veris 3100 Sensor

Authors
item Jabro, Jalal "jay"
item Evans, Robert
item Stevens, William
item Iversen, William

Submitted to: ASABE Annual International Meeting
Publication Type: Proceedings
Publication Acceptance Date: June 1, 2006
Publication Date: July 1, 2006
Citation: Jabro, J.D., Evans, R.G., Stevens, W.B., Iversen, W.M. 2006. Repeatability of soil apparent electrical conductivity measured by the Veris 3100 Sensor. ASABE Annual International Meeting, July 9-12, 2006. Portland, Oregon. 2006 CD-ROM.

Interpretive Summary: Repeatability of a measurement can be assessed by characterizing the variation between successive measurements of the same quantity. Apparent electrical conductivity (ECa) offers advantages for mapping soil variability because detailed data can be colleted easily and inexpensively using on-the-go EC sensors; however, there has been little research investigating the repeatability of these sensors. The objective of this study was to evaluate the repeatability of the coulter sensor by comparing ECa data from two passes in barley stubble at two 1.6-ha sites, one with a sandy loam soil texture (Nesson) and the other a clay loam soil texture (EARC). The ECa measurements from both passes were compared at shallow (0-30 cm) and deep (0-90 cm) soil depths. The CVs of ECa measurements for shallow and deep depths from pass1 were higher than those from pass2 at both sites. The (RMSE values of ECa measurements between pass1 and pass2 at shallow and deep depths for the Nesson site were 0.76 and 0.51, respectively, while, the RMSE for the EARC site were 4.06 and 2.93 at shallow and deep depths, respectively. The repeatability was evaluated using a 95% confidence interval for the difference between ECa measurements of the two passes. Results demonstrate marginally unacceptable repeatability between the two passes at shallow depth for both sites and acceptable repeatability at deep depths. The reasons for lack of agreement between pass1 and pass2 in ECa measurements at shallow depths could have resulted from soil disturbance and compaction caused by the coulter sensor during pass1 process.

Technical Abstract: Repeatability of a measurement can be assessed by characterizing the variation between successive measurements of the same quantity. Apparent electrical conductivity (ECa) offers advantages for mapping soil variability because detailed data can be colleted easily and inexpensively using on-the-go EC sensors; however, there has been little research investigating the repeatability of these sensors. The objective of this study was to evaluate the repeatability of the coulter sensor by comparing ECa data from two passes in barley stubble at two 1.6-ha sites, one with a sandy loam soil texture (Nesson) and the other a clay loam soil texture (EARC). The ECa measurements from both passes were compared at shallow (0-30 cm) and deep (0-90 cm) soil depths. The CVs of ECa measurements for shallow and deep depths from pass1 were higher than those from pass2 at both sites. The (RMSE values of ECa measurements between pass1 and pass2 at shallow and deep depths for the Nesson site were 0.76 and 0.51, respectively, while, the RMSE for the EARC site were 4.06 and 2.93 at shallow and deep depths, respectively. The repeatability was evaluated using a 95% confidence interval for the difference between ECa measurements of the two passes. Results demonstrate marginally unacceptable repeatability between the two passes at shallow depth for both sites and acceptable repeatability at deep depths. The reasons for lack of agreement between pass1 and pass2 in ECa measurements at shallow depths could have resulted from soil disturbance and compaction caused by the coulter sensor during pass1 process.

Last Modified: 4/19/2014
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