Few Idaho environments and small grain production systems can support maximum production without supplemental watering, especially in southern Idaho. In all systems it is generally the most limiting factor to both production and quality. In irrigated systems it is a significant production cost if not the single greatest production expense of an enterprise. Optimal irrigation maximizes the economic returns to the enterprise while minimizing adverse effects on water quality.
Irrigation has substantial effects on other crop production elements including fertilizer use efficiency, diseases and weed control. Irrigation needs to be considered in relation to these other elements. This is particularly critical for soluble and mobile nitrogen (N) such as nitrates that are easily leached with the wetting front beyond the reach of the root system. Excessive irrigation leads to additional or higher N applications, reduced financial returns and greater potential for ground water contamination.