Farmer adaptation of intermittent flooding using multiple-inlet rice irrigation in Mississippi

Although intermittent flooding of rice (Oryza sativa L.) has been shown to significantly reduce irrigation demand, farmer adoption is limited in the United States where continuous flooding remains standard practice. This limited extent of adoption stems in part from a number of scalability and agronomic concerns. This study used replicated trials established in farmer-managed fields to determine if intermittent flooding can be successfully adapted to commercial-scale rice production in Mississippi. When intermittent flooding was coupled with multiple-inlet rice irrigation (MIRI), the quantities and qualities of yields were maintained or increased for five commercial rice varieties and one hybrid, relative to continuously-flooded controls. Only CL151 exhibited a decrease in total head rice when milled, this after being subjected to five or more wetting and drying cycles over ≈80 day flood periods. Water use over three years averaged 32% less than comparable MIRI systems not using intermittent flooding. These results demonstrate that intermittent flooding can be successfully adapted by producers to commercial-scale and that 600 mm irrigation is an achievable goal for rice grown on clay soils in Mississippi. The positive yield responses of CL162 to intermittent flooding and pre-flood urea-nitrogen support research showing that rice benefits from carefully managed wetting- and drying-periods when used in conjunction with effective pest management. The success of these producers at adapting intermittent rice flooding to commercial scale can be attributed in part to their having comprehensive weed and disease management programs, proficiency in using MIRI, and reliable irrigation systems with ample well capacities that allowed rapid flood establishment. Even partial adoption of intermittent rice flooding can increase rainfall capture and reduce demand for irrigation. In turn, this could help to alleviate overdraft of the Mississippi River Valley Alluvial aquifer, a resource of national and international significance.