Expected Irrigation Reductions Using Multiple-Inlet Rice Irrigation under Rainfall Conditions of the Lower Mississippi River Valley

Multiple-inlet rice irrigation (MIRI) decreased irrigation applications by an average of 24% over an 86-day flood when compared to single-inlet (SI) rice flood distribution. Even in the absence of rainfall, MIRI required 22% less irrigation than SI when generalized water-balance equations were used to simulate irrigation use in a 16-ha, clay soil, straight-levee field typical of the Lower Mississippi River Valley (LMRV). The majority of MIRI savings was due to improved distribution uniformity that results in less runoff rather than increased rainfall capture. Using 260 site-years of rainfall from nine LMRV locations, these results also suggest that the wide variability in irrigation use observed in MIRI field trials is not due to variations in rainfall alone. Rather, other factors such as management style and field conditions likely impact irrigation use as much, if not more than, year-to-year variations in rainfall. Taken together, these results reinforce university extension efforts that educate farmers on the importance of irrigation management in realizing the water-conserving benefits of MIRI. Further, the results support efforts to automate irrigation monitoring and pump control by showing that significant irrigation savings occur with MIRI when pumping is halted in a timely manner.