Submitted to: Proceedings of the American Society of Agricultural and Biological Engineers International (ASABE)
Publication Type: Proceedings
Publication Acceptance Date: August 10, 2005
Publication Date: October 5, 2005
Citation: Jabro, J.D., Evans, R.G., Kim, Y., Stevens, W.B., Iversen, W.M. 2005. Spatial variability of the apparent electrical conductivity and cone index as measured with sensing technologies: assessment and comparison. ASABE Pacific Northwest Section Meeting, Lethbridge, Alberta, Canada, September 22-24, 2005. Paper PNW05-1017. Technical Abstract: Assessment and interpretation of the spatial variability of soil chemical and physical properties is very important for precision farming. The spatial variability of apparent electrical conductivity (ECa) and Cone Index (CI) for soil compaction was investigated with Veris 3100 and Profiler 3000 sensing technologies. The study was conducted in April 2005 at the ARS-research farm located near Williston, ND on a sandy loam soil. Measurements of soil ECa were taken using Veris 3100 on a parallel swathing monitored with the DGPS unit providing spatial coordinates for each measurement at shallow (0-30 cm) and deep (30-90 cm) depths. A Profiler 3000 equipped with the GPS unit was also used to collect measurements of ECa and CI that were recorded in 2 cm intervals to a depth of 90 cm on a grid sampling system. The experimental plot area mapped with this technology was approximately 1.4 ha. The ECa data from both Veris 3100 and Profiler 3000 exhibited similar spatial trends across the field that may characterize the variability of soil for a variety of important physical and chemical properties. The coefficient of variations of ECa from Veris 3100 and Profiler 3000 were 19.2 and 11.3%, respectively. However, the averages of ECa measurements for Veris 3100 and Profiler 3000 were 4.92 and 3.31 mS/m, respectively that were significantly different. The ECa mean difference, Md between these two devices was also significantly different from zero (Md= 1.71 mS/m; t=34.23, n=138; pr<0.0001). Geostatistical techniques and parameters will also be used to further investigate this spatial dependency and assess the overall soil variability. Further, ECa measurements from both techniques exhibited approximately log normal distribution and the CI values were normally distributed using probability distributions.