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Irrigation threshold and cover crop impacts on corn production in Mississippi
Proceedings of the 2022 Mississippi Water Resources Conference

Year: 2022 Authors: Russell D., Kaur G., Singh G.

The Mississippi River Valley Alluvial Aquifer (MRVAA) is the main source of groundwater for irrigation in the Mississippi Delta region. Increases in irrigated crop acreage, as well as frequent droughts throughout the growing season, have caused continual groundwater decline in this aquifer. The objective of this study was to determine if combinations of irrigation scheduling thresholds (-40 kPa, -90 kPa, and no irrigation control) and cover crops [cereal rye (Secale cereale L.), hairy vetch (Vicia villosa R.), wheat (Triticum aestivum L.) + radish (Raphanus sativus L.) + turnip (Brassica rapa L.) mix, and no cover crop control] could improve corn grain yield and quality, water productivity, and irrigation water use efficiency. A field experiment was conducted from 2019 to 2021 at the National Center for Alluvial Aquifer Research in Leland, MS, and the experimental design comprised of a randomized complete block with four replications. In 2020, cover crops reduced corn yield by 9 to 26% compared to the no cover crop control. Minimal or negative impacts from cover crops were also observed for water productivity, irrigation water use efficiency, and corn grain quality in the first year of the study. In 2021, -40 kPa irrigation treatments had 8 and 9% higher corn yield compared to no irrigation and -90 kPa irrigation treatments, respectively. No irrigation treatments showed 6 and 17% higher water productivity compared to -90 kPa and -40 kPa, while hairy vetch was at least 7% higher in water productivity among cover crop treatments in year two of this study. While cover crops showed improvements over the course of two years, no cover crop treatments under the -90 kPa irrigation threshold was the most profitable treatment when averaged over both years. Continued evaluation of cover crops and irrigation thresholds is needed to determine which combination is best for corn production in the Mississippi Delta region.

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