Towards Spatial Irrigation Management Using Distributed Soil-Water Tension Measurements Optimized for Soil Heterogeneity.

Proper irrigation management is essential for economically-sound crop production in arid and semi-arid climates using a modus operandi such that the timing and amount of irrigation water applied match crop water needs.  High-value crops that are sensitive to water stress such as potatoes coupled with economic incentives on resource inputs have led to the adoption of feedback mechanisms aimed at conserving water and nutrients while maintaining yield.  Given these economic pressures on irrigated agriculture, it is vital to evaluate tension-based irrigation while incorporating soil and hydraulic variability within the field. The objectives of this study were to (1) evaluate and assess the within field variability in soil properties and irrigation uniformity, and (2) evaluate the irrigation water deficit to determine an optimal irrigation scheme based on soil-water tension feedback to meet crop-water needs while considering spatial variability.  We collected electrical conductivity data using electromagnetic induction throughout the growing season along with sprinkler efficiency data using catch cans.  These data were used to select sites for the collection of calibration data including soil and hydraulic properties in addition to a distributed soil-water tension and water content network.  Preliminary results suggest that an integrated ET, crop need and tension-feedback driven irrigation management using tension-thresholds optimized for hydro-zones may yield significant economic benefits.  In addition, the knowledge gained from this project has demonstrated improved agronomic performance to growers and extension agents.