Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 11/3/1995
Publication Date: N/A
Technical Abstract: A shallow clay layer may influence rooting depth and water and chemical movement. Mapping the depth to clay across a field is laborious and costly when a soil probe is used. For soils with contrasting electrical conductivities for the clay and overlaying soil layers, electromagnetic induction (EMI) measurements can in theory be used to predict not only the depth to clay but also the electrical conductivities of the two layers. Estimates are made by combining EMI measurements at various heights above the ground with the meter's response function using nonlinear curve fitting techniques. We tested the fully predictive EMI technique by making measurements at 0.0, 0.2, 0.4, 0.6, and 0.8 m above the ground surface at 164 grid locations in a 65 ha field in central Kansas. The field consisted of wind blown sand overlying a clay layer at variable depth. Comparisons between the EMI predicted depth to clay and measurements made with a soil probe were not very good. The fully predictive method was inconsistent in predicting locations with shallow depth to the clay. Simple linear regression using measurements at a single height gave more reliable estimates with correlations of about 0.7.