Investigating soybean (Glycine max L.) responses to irrigation on a large-scale farm in the humid climate of the Mississippi Delta region

Authors: Anapalli, Saseendran; PINNAMANENI, SRINIVASA - Oak Ridge Institute For Science And Education (ORISE); Reddy, Krishna; Sui, Ruixiu; SINGH, GURBIR - Mississippi State University

Submitted to: Agricultural Water Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/21/2021
Publication Date: 3/31/2022
Citation: Anapalli, S.S., Pinnamaneni, S., Reddy, K.N., Sui, R., Singh, G. 2022. Investigating soybean (Glycine max L.) responses to irrigation on a large-scale farm in the humid climate of the Mississippi Delta region. Agricultural Water Management. 262:107432. https://doi.org/10.1016/j.agwat.2021.107432.
DOI: https://doi.org/10.1016/j.agwat.2021.107432

Interpretive Summary: The survival of irrigated agriculture in the Lower Mississippi Delta region today hinges on enhancing productivity of the water pumped out of the shallow Lower Mississippi Valley Alluvial Aquifer, which is drying up from unsustainable water extractions for irrigations. Scientists in Sustainable Water Management Research Unit of USDA ARS in Stoneville, MS, investigated soybean productivity in clay soil in response to irrigations applied through every furrow, applied through alternate furrow, and rainfed (unirrigated) in the region. About half of the water applied in every furrow irrigations were applied in the alternate furrow irrigations. The experiments were conducted in farm-scale fields (15 ha). There was no significant difference in measured soybean grain yield between the alternate furrow and all furrow irrigated fields. However, rainfed fields produced on average 24% less soybean grain yields. The study proved that irrigating the crops through alternate furrows yields equally or better than irrigating through every furrow, saving about half the water pumped out of the aquifer for irrigations.

Technical Abstract: The shallow Lower Mississippi River Valley Alluvial Aquifer, which supports irrigated agriculture in the Lower Mississippi Delta (LMD) region, is fast depleting from unsustainable water extractions for irrigations. The survival of irrigated agriculture in the region today hinges on enhancing the irrigation use efficiencies of the water pumped out. Furrow irrigation practices (surface or flood irrigation) dominate the LMD region's irrigated agriculture scenario. We investigated soybean productivity in response to irrigations applied through every furrow (FI), applied through alternate furrow (AFI), and rainfed (RF, no irrigation). Approximately half the volume of water applied in FI was applied in the AFI. The experiments were conducted in 2016, 2018, and 2020, which constituted the soybean phases of a corn-soybean rotation trial conducted in clay soil in farm-scale plots (15 ha). The plots were equipped with eddy covariance systems for quantifying crop water use (ET, evapotranspiration). There was no appreciable difference in soybean grain yield between FI and AFI, but RF yielded significantly lower than FI and AFI. Leaf area index was also significantly smaller in RF. Across the three years, the average reduction in soybean yield was only 2% in AFI, while it was 24% in RF compared to FI. Average grain yields were 4507, 4413, and 3422 kg ha-1; seasonal ET were 549, 562, and 527 mm; and water use efficiencies (WUE) were 8, 8, and 7 kg ha-1 mm-1 in FI, AFI, and RF, respectively. This large farm-scale study demonstrated that irrigating soybean through alternate furrows yields like irrigating through every furrow, saving about half the water pumped out of the aquifer.