|18th World Congress of Soil Science
July 9-15, 2006 - Philadelphia, Pennsylvania, USA
2. Calibrating EC values for texture class prediction. The bulked EC values of the EM38 sonde can be related to texture classes of soil profiles only after calibration by soil augering to 15 dm depth (with “SoilRover” hydraulic borer). Lo-cal deviations of temperature and moisture regimes from standards are corrected by thumb rules (3% and 5% of EC per 1oC. or 1% water, resp.). Also organic matter enrichments (bog-soils) may have specific effects on the EC values and need to be verified. As a regional exam-ple of calibration, the EC ranges of texture classes are given in table 1.
3. Uses of the sensor based soil surveys. With a limited number of calibrating auger profiles (~1/ha) very detailed soil inventories for texture (or clay) profile maps can be achieved. Due to correlations (coefficient r, see table 1) of EC to crop yields and to soil parameters (AWC, CEC: available water and cation exchange capacities in 0-1m depth) several special purpose maps can be constructed for precision farm-ing or soil protection projects, e.g. detailed maps for (a) soil specific liming and base fertil-izer applications (P-, K-,Mg-/Ca-nutrients), (b) target yield based variable seeding and nitro-gen fertilization, (c) variable tillage depth, depending on clay in Ap (with caution, if soil is stratified), (d) tile drain width which relates to texture classes, (e) water percolation rates and nitrogen leaching risks (depending on AWC).