Only about 16% of the US corn crop is irrigated and almost no irrigated corn is used as ethanol feed stock.
It’s time to re-think corn irrigation.
corn farmer... in the 1950s when Georgia farmers averaged 25 bushels per acre...
the times and technology have changed. Georgia averaged 130 bushels per acre in 2007, and...there are other reasons, including improved hybrids, better fertilization, improved weed control, and other factors for Georgia’s better corn yields.
Irrigation requires a relatively high investment in equipment, fuel, maintenance and labor, but it offers a significant potential for increasing net farm income. Frequency and timing of water application have a major impact on yields and operating costs.
http://southeastfarmpress.com/its-time-re-think-corn-irrigation