Cover crops and furrow irrigation impacts on soybean production in sub-humid climate

Authors: RUSSELL, DILLON - Mississippi State University; SINGH, GURBIR - University Of Missouri; QUINTANA-ASHWELL, NICOLAS - Mississippi State University; KAUR, GURPREET - University Of Missouri; GHOLSON, DREW - Mississippi State University; KRUTZ, JASON - Mississippi State University; NELSON, KELLY - University Of Missouri

Submitted to: Agricultural Water Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/1/2023
Publication Date: 5/11/2023
Citation: Russell, D., Singh, G., Quintana-Ashwell, N., Kaur, G., Gholson, D.M., Krutz, J.L., Nelson, K.A. 2023. Cover crops and furrow irrigation impacts on soybean production in sub-humid climate. Agricultural Water Management. https://doi.org/10.1016/j.agwat.2023.108347.
DOI: https://doi.org/10.1016/j.agwat.2023.108347

Interpretive Summary: Declining groundwater levels in the Mississippi River Valley Alluvial Aquifer make it urgent to find more and better ways to conserve groundwater while maintaining crop productivity. A study was conducted from 2019 to 2021 to determine the combination of cover crop (CC) and irrigation sensor threshold that maximizes soybean yield, irrigation water use efficiency, water productivity, and farm profitability. The CC treatments were cereal rye , hairy vetch, wheat, radish-turnip mix, and no-CC. The irrigation thresholds used for irrigation scheduling were a wet threshold, a dry threshold, and no-irrigation. Soybean yield was highest (6021 kg/ha) following hairy vetch CC under the wet irrigation threshold in 2020, but no differences were observed in 2021. Water productivity was lower under the wet irrigation threshold than all other treatments in 2020, and at least 23% lower in wet threshold treatments than the dry threshold treatments in 2021. Irrigation water use efficiency was higher under the dry irrigation threshold than the wet irrigation threshold in 2020. When averaged over two years, cover crops results in reduced economic returns compared to no-CC under all irrigation treatments except for wheat-radish-turnip mix under the dry threshold treatments. Our results suggest that long-term evaluation is needed to study the impact of CCs under different irrigation regimes. This work contributes to the understanding of the nuances of cover crop usage in different production settings.

Technical Abstract: Declines in the Mississippi River Valley Alluvial Aquifer make it urgent to find more and better ways to conserve groundwater levels and maintain crop productivity. This study was conducted from 2019 to 2021 to determine the combination of cover crop (CC) and irrigation sensor threshold that maximizes soybean (Glycine max L.) yield, irrigation water use efficiency (IWUE), water productivity (WP), and farm profitability. The CC treatments were 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-CC. The irrigation thresholds used for irrigation scheduling were a wet threshold (-40 kPa), a dry threshold (-90 kPa), and no-irrigation. Soybean yield was highest (6021 kg ha-1) following hairy vetch CC under the wet irrigation threshold in 2020, but no differences were observed in 2021. Water productivity was lower under the wet irrigation threshold than all other treatments in 2020, and at least 23 % lower in wet threshold treatments than dry threshold treatments in 2021. Irrigation water use efficiency was higher under the dry irrigation threshold than the wet irrigation threshold in 2020. When averaged over two years, CC's reduced economic returns than no-CC under all irrigation treatments except for wheat-radish-turnip mix under the dry threshold treatments. Our results suggest that long-term evaluation is needed to study the impact of CCs under different irrigation regimes.