Investigating Soybean Responses to Irrigation Through Farm-Scale Trials in the Mississippi Delta

Investigators: Saseendran Anapalli, Srinivasa Pinnamaneni, Krishna Reddy, Ruixiu Sui, Gurbir Singh

Date: 2021

Project Summary

Introduction

The future of irrigated agriculture in the Lower Mississippi River Basin (LMRB) hinges on enhancing irrigation water use efficiency. Furrow irrigation practices dominate irrigated agriculture in the LMRB. We investigated soybean productivity in response to irrigation applied through every furrow (FI), irrigation applied through alternate furrow (AFI), and rainfed production (RF; no irrigation). Approximately half the volume of irrigation water applied to the FI treatment was applied to the AFI treatment. The experiments were conducted in 2016, 2018, and 2020, which constituted the soybean phases of a corn-soybean rotation trial conducted on a clay soil in field-scale plots (25 ac). The plots were equipped with eddy covariance systems for quantifying crop water use (i.e., evapotranspiration (ET)). This unique study was conducted at the farm scale; as such, the results obtained directly apply to a farm environment, so they are ready to be incorporated into recommendations for adoption by soybean farmers without further field trials.

Materials and Methods

To generate confident recommendations for adopting technologies previously developed in small-plot experiments, those experiments should be repeated at multiple locations and climates in field-scale plots. Such farm-scale trials provide the opportunity to evaluate irrigation water management technologies under realistic farming conditions. Another reason for farmscale experiments is the three-dimensional spread of irrigation water. As the water applied to the furrows spread in all directions, irrigation in one small plot may unintentionally affect neighboring small plots. These interferences can be avoided by implementing treatments on larger field-scale plots. The multi-year experiment was an irrigated corn-soybean rotation conducted between 2016 and 2020 at the United States Department of Agriculture (USDA)-Agricultural Research Service (ARS) Crop Production Systems Research Unit farm in Stoneville, MS. The investigation aimed to evaluate soybean production responses to FI, AFI, and RF scenarios and to quantify the water used by the crop in these systems using the cutting-edge science-based Eddy Covariance technology. A mid-maturity group IV soybean cultivar, Dyna-Gro 31RY45, was planted in the experiments without applied fertilizers.

Results and Discussion

Daily crop water use (ET) averaged across the three seasons were 0.193”, 0.197”, and 0.185”, respectively, in the FI, AFI, and RF treatments. Seasonal (emergence to R7 stage) ET in the three treatments were 21.2”, 22.1”, and 20.7”, respectively. Averaged across the three crop seasons, seasonal rainfall was 19.4” while seasonal irrigation to the AFI and FI treatments were 1.6” and 3.2”, respectively. Soybean yields across the three crop seasons in the FI, AFI, and RF treatments were 67.0, 65.6, and 50.9 bu/ac, respectively. Yield in the AFI treatment was only 1.4 bu/ac less than in the FI treatment, which means only a 2% yield decrease.

Conclusion

Using eddy covariance-based sensors in large field-scale plots, we quantified water used by soybean in the FI, AFI, and RF treatments. Irrigation through every furrow and alternate furrow, when combined with natural rainfall receipts and soil water storage, supplied enough water for the optimum production of the crop. Consequently, soybean grain yields were similar in the FI and AFI treatments. The RF treatment consumed less water; however, it yielded significantly lower as well. These farm-scale trials in the LMRB indicated that soybean can be irrigated through alternate furrows to save about half the irrigation water while producing comparable grain yields. This study is being continued for quantifying irrigation responses of corn, cotton, and rice across major soils and climates in the region for developing decision support information for sustainable water management.

Project Photos

• Crop Type:
• Soybean

• Topic:
• Irrigation Scheduling
• Irrigation