Long-term measurements of agronomic crop irrigation made in the Mississippi delta portion of the lower Mississippi River Valley

With over 4 million ha irrigated cropland, the Lower Mississippi River Valley is a highly productive agricultural region where irrigation practices are similar and the Mississippi River Valley alluvial aquifer (MRVA) serves as a primary source of on-demand irrigation. The power conversion coefficient method was used to measure season-long irrigation applied by producers to cotton, maize, rice, and soybean grown in the Mississippi Delta over a 12-year period that spanned a range of weather and cropping conditions. Averaged across all years and irrigation methods, irrigation rates were 9200, 3100, 2800, and 1800 m3 ha−1 for rice, maize, soybean, and cotton, respectively. Pivot and flood methods resulted in the lowest application rates when compared to furrow irrigation of row crops. In terms of rice, zero-grade fields received the least irrigation while multiple-inlet rice irrigation reduced irrigation by 19% relative to cascade flooding. No differences were measured between contour- and straight-levee rice fields. Irrigation rates for cotton and rice remained unchanged over time. Maize-soybean rates increased by approximately 200 m3 ha−1 y−1 and correlated (r > 0.67) with cumulative moisture deficit at Stoneville. Study results provide irrigation rates necessary to calculate detailed water budgets for the MRVA. These data may also serve as benchmarks for irrigation performance evaluations.