Cumulative deficit irrigation effects on corn biomass and grain yield under two tillage systems

Deficit irrigation (DI) is sometimes used to cope with dwindling irrigation water supplies or limited water allocations. A study at Akron, Colorado, USA from 2001 to 2006 investigated the effects of consecutive years of DI on soil water use, soil water content, biomass production, grain yield and water use efficiency (WUE) in a continuous corn system. In 2001, DI and full irrigation (FI) had the same grain yield. In 2002, DI reduced grain yield by 20% relative to FI. By 2006, continued DI reduced grain yield by 65% compared with FI. Significant increases in soil water storage during the non-crop period occurred only in 2005 and 2006. This resulted in a slow but continual decrease in soil water storage as the years progressed. By 2006, soil water storage in the 60- to 90-cm depth remained lower for DI than for FI during the entire growing season. WUE declined for DI compared with FI over the years. WUE was the same for DI and FI in 2001, but WUE for DI declined to only 65% of FI by 2006. DI may be an option for short term or emergency situations when insufficient irrigation water is available for FI in one year. However, long-term use of DI, without replenishment of stored soil water during the non-cropped period, was detrimental to both corn production and water use efficiency under these experimental conditions.