Seasonal variations in net ecosystem exchange of CO2 and conservation of water use efficiency in the mississippi delta

Authors: Anapalli, Saseendran; Bhandari, Ammar; ADIREDDY, RAJANNA - Oak Ridge Institute For Science And Education (ORISE); Reddy, Krishna

Submitted to: Scientific Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/31/2025
Publication Date: 5/8/2025
Citation: Anapalli, S.S., Bhandari, A.B., Adireddy, R.G., Reddy, K.N. 2025. Seasonal variations in net ecosystem exchange of CO2 and conservation of water use efficiency in the mississippi delta. Scientific Reports. Volume8, Issue2. https://doi.org/10.1002/agg2.70109.
DOI: https://doi.org/10.1002/agg2.70109

Interpretive Summary: The balance between the amount of carbon dioxide absorbed by crops through photosynthesis and released back into the atmosphere through respiration is known as the net ecosystem exchange (biomass production) of carbon dioxide. Through this process, plants and soil remove carbon dioxide in the air that causes global warming and store it away in soil-plant systems. The efficiencies of the water pumped for irrigation in producing biomass and yield of interest (for example, cotton lint) are known as their water use efficiencies. Accurately quantifying the net ecosystem exchange is critical for developing alternative climate-smart farm management strategies to enhance carbon storage and adapt and reduce climate change impacts. In this context, scientists with the Crop Production Systems Research Unit, USDA ARS, Stoneville, MS, conducted a multi-year study in large farm-scale fields and assessed the carbon storage potential of cotton and their water use efficiency. The cotton cropping system effectively captured and stored atmospheric carbon dioxide in cotton biomass and the lint. There appears to be less hope in reducing water used in producing cotton lint by reducing crop water consumption. However, improving water saving through more efficient irrigation water delivery and application techniques in cotton production systems may be possible.

Technical Abstract: Accurately quantifying the net ecosystem exchange of CO2 (NEE) is a critical prerequisite for developing alternative farm management strategies to enhance carbon sequestration in biological systems and reduce greenhouse gas emissions. A two-year study quantified the NEE of CO2 from cotton (Gossypium hirsutum L.) on silty clay in farm-scale fields using an eddy covariance approach (EC). On a seasonal scale, NEE and evapotranspiration (ET) were 8,836 kg CO2 ha-1 and 367 mm, respectively, in 2017, and 10,759 kg CO2 ha-1 and 430 mm, respectively, in 2018. Harvested cotton lint yields were 1,269 and 1,569 kg ha-1 in 2017 and 2018, respectively. The water use efficiency (WUE) for lint production (WUElint) and ecosystem level WUE for NEE (WUENEE) across the two seasons was nearly constant. WUElint were 3.5 kg lint ha-1 mm-1 and 3.6 kg lint ha-1 mm-1, respectively, in 2017 and 2018, and WUENEE were 24 kg CO2 ha-1 mm-1 and 25 kg CO2 ha-1 mm-1. The NEE and WUE measured in this study can be used as a benchmark for comparing carbon sequestration potential in cotton production. However, further research is needed to understand NEE responses to long-term climate variability and to develop climate-smart crop-soil management strategies.