Content area
Full text
Mapping electrical conductivity in soil shows soil-to-yiel relationship.
If you're optimistic about the theory of variable rate inputs based on grids/soil types, you may want to check out the latest technology for finite soil measuring, which identifies soil electrical conductivity (EC). Precision farming practitioners and their consultants are looking to soil EC as a way to more precisely define soil type and patterns across fields.
"Soil EC readings are light years ahead of the soil survey manuals," says Dan Kaminsky, sales agronomist with Helena Chemical. "The data give us a better way to draw in soil boundaries and create management zones by soil type:'
One of his customers, John Nidlinger, Decatur, IN, has completed 1-acre grid sampling on the majority of his 2,200 tillable acres but sees value in soil EC data. "Measuring soil EC . . . has given us a much more accurate measurement of changes in our soil types," he says. "When we compared our soil EC maps to four years of yield maps, we found a relationship between high EC readings and lower yields. This is another major link in understanding our soils. It's an important part of the precision a information package."
What is soil EC?
Electrical conductivity is the ability of a material to conduct an electrical current. Soil EC has no direct effect on crop growth or yield. "The utility of EC mapping comes from the relationships that frequently exist between EC and a variety of other soil properties that are highly related to crop productivity," says Tom Doerge, precision farming agronomist for Pioneer Hi-Bred International. These properties include water-holding capacity, topsoil depth, cation exchange capacity (CEC), soil drainage, organic matter level, soil nutrient levels and subsoil characteristics.
EC readings correlate strongly to soil grain size or texture. Sand has low conductivity, silts have a medium conductivity and clays have a high conductivity.
Induction or direct contact methods
The two primary methods of measuring so conductivity are by electromagnetic induction (EMI) or by direct contact. A contact method from Veris Technologies uses at least four electrodes that are in physical contact with the soil to inject a current and measure the voltage that results. An EMI sensor does not make contact but instead uses a transmitter coil...