"When do I turn the irrigation water on?, and How long do I leave it on?" Getting the answer to these questions right has tremendous public and private benefits including better plant growth and crop yields, improved crop quality, lower water use, lower pumping energy costs, lower labor costs, and decreased losses of costly fertilizers to leaching.

This is a simple, free, user-friendly, and mobile irrigation scheduling tool to help irrigators know much more precisely how much to irrigate and when.

Irrigation Scheduler Mobile works in Washington, Oregon, Idaho, California, Nevada, Arizona, Montana, Utah, Colorado, North Dakota, and South Dakota. It both works as a native app, a web app, and as a stand alone web site (at http://weather.wsu.edu/ism) for access from anywhere. It was designed for agricultural use, but also works great for lawns, gardens, or turfgrass. It is easy to set up a field and automatically pulls daily crop water use (evapotranspiration, or ET) estimates from agricultural weather station networks to estimate your daily soil water deficit. The user just needs to input how much they irrigated on a particular date throughout the season.

It allows modifications for improved accuracy by more educated users. The model can be corrected at any time using soil water measurements or estimates. It readily displays useful charts and tables for visual evaluation of soil water status and irrigation or rainfall.

Full documentation is available at http://weather.wsu.edu/ism/ISMManual.pdf.