Submitted to: Colorado State University Newsletter
Publication Type: Popular Publication
Publication Acceptance Date: November 12, 2002
Publication Date: N/A
Technical Abstract: The idea of automated in-field sensors for assessing soil nutrients is appealing because of the difficulty in obtaining a representative sample with traditional methods. With sensors, many more measurements could be taken than is feasible with soil sampling and lab analysis. In recent years, a sensor that has received a lot of attention for helping assess soil nutrients is soil electrical conductivity (EC). Soil EC is a measure of the soil's ability to transmit or conduct an electrical current. There are two primary techniques used to measure profile soil EC in the field, electromagnetic induction (EM) and electrode contact. While measurements with the two types of soil EC sensors are comparable, differences are expected since the depth of sensing is unique to each sensor. Soil EC is a measurement that is correlated to a number of properties affecting soil water, such as texture, drainage conditions, and salinity. This soil EC/soil water connection is why patterns in a yield map are often visually similar to patterns seen in a soil EC map. Further, soil EC can be affected by properties of the soil that help characterize soil nutrients, such as cation exchange capacity (CEC) and soil organic matter. In some situations, soil EC can vary with differing levels of soil pH, soil nitrates, and other soil nutrients associated with repeated manure applications. The value of soil EC is in itself site-specific and can only be determined for a location with soil sampling to calibrate what is causing soil EC to vary within a field. Soil EC can help producers be smarter about where soil samples are taken, potentially reducing the number of samples taken. Interest in soil EC will continue to grow as producers embrace precision agricultural concepts.