A fair amount is going into Iowa to irrigate grow-out fields for genetics comnpanies. They figure that it will pay off big in 2-3 years out of 10 - but suspect that it will be more useful than that by resolving timing issues. Best way to find closest users is to find the local distributors/installers for drip irrigation tubing and ask them.

 Best site for questions is Trickle-L list serve. http://www.ars.usda.gov/is/AR/archive/may97/trickle0597.htm