Seasonal Crop-Water Use Estimation Using Time-Lapse Measurements of ECa in Wheat, Barley and Pea Production with Varying Topography.

Dryland crop production relies on accurate predictions of available soil water at the time of planting.  In regions with marginal precipitation, growers use crop rotations and surface preparation practices to build soil-water natural capital over preceding seasons to facilitate cash crop production.  However, significant gaps exist in identifying transfer functions that link soil properties and agronomic practices to crop-water use, and to predict temporal changes in soil water storage because of major uncertainties in complex interactions.  Some of these complex interactions are between spatial variability in soil properties, topography and crop management which often express themselves as complex spatiotemporal functions in soil water storage.  In this study we used time-lapse electromagnetic induction to measure apparent electrical conductivity of variably saturated soils to infer spatiotemporal variability of soil water while comparing chisel plow tillage and no-till as well as crop rotations on a split-plot design in the Palouse region of Northern Idaho. Separating factors of temporal stability and variability allowed us to derive calibrated relationships between water content with additional variables growing degree days, elevation, clay content, and silt content which suggest that spring peas retained the highest water content, followed by spring barley and winter wheat.  Our results benefit growers by providing a decision-support tool to quantify and predict stored soil water prior to planting.