Site-Specific Variable-Rate Irrigation as a Means to Enhance Water Use Efficiency

The majority of irrigated cropland in the U.S. is watered with sprinkler irrigation systems. These systems are inherently more efficient in distributing water than furrow or flood irrigation. Appropriate system design of sprinkler irrigation equipment, application methods, and farming practices (e.g., furrow diking) enhance crop water use efficiency (WUE) by minimizing irrigation losses and improving soil water storage. For years, the paradigm for best irrigation management practices included uniform application over an entire field, even though abiotic (soils, slope, aspect, etc.) and biotic (insect pressure, plant disease) factors often cause spatial variations in water use and yield potential. However, emerging technologies such as wireless communication coupled with soil water and plant sensors, commercially available variable-rate irrigation (VRI) equipment, and the development of algorithms for computational data processing are shifting this paradigm toward variable-rate management as a means to enhance crop WUE. This article focuses on the potential of site-specific VRI management (SS-VRIM) as a tool for enhancing WUE and the challenges encountered.