No-till impacts on soil organic carbon and SMAF soil quality in the Lower Mississippi River Basin: Implications for sustainable management

Authors: AMORIM, HELEN - University Of Arkansas; Ashworth, Amanda; Mubvumba, Partson; SAVIN, MARY - University Of Arkansas; Anapalli, Saseendran; Reddy, Krishna

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/17/2024
Publication Date: 6/21/2024
Citation: Amorim, H., Ashworth, A.J., Mubvumba, P., Savin, M.C., Anapalli, S.S., Reddy, K.N. 2024. No-till impacts on soil organic carbon and SMAF soil quality in the Lower Mississippi River Basin: Implications for sustainable management. Soil Science Society of America Journal. Article e220717. https://doi.org/10.1002/saj2.20717.
DOI: https://doi.org/10.1002/saj2.20717

Interpretive Summary: Since the advent of agriculture, tillage, or the mechanical disturbance of soil that leaves less than 30% of crop residue on the soil surface, has been employed to control weeds. However, repeated tillage over decades reduces stable soil carbon and can create a positive-feedback for climate-warming gases by converting arable soils from a carbon sink to a carbon source. In turn, benefits of employing no-till include: reduced erosion, improved soil biodiversity, improved soil health due to stable aggregation, and lesser nutrient losses to the air, soil, and water. However, rates of SOC storage from no-till and subsequent soil quality and crop yields remain largely unknown in the Mississippi Delta as this region has one of the lowest non-tillage adoption rates in the US. Therefore, researchers set out to evaluate soil nutrient and carbon changes, yield, and soil quality following 15 years of continuous tillage vs. non-tillage management. This study found that non-tillage resulted in 25% greater soil carbon than conventionally tilled soils, resulting in great overall soil health scores for the non-tillage system. Consequently, non-tillage is a climate-smart management practice that allows for sustainable intensification in the Mississippi Delta region.

Technical Abstract: No-till (NT) reportedly alleviates adverse effects of agricultural production on environmental quality, improves soil health, and reduces net greenhouse gas emissions, yet this has not been demonstrated in humid subtropical Mississippi. Research objectives were to evaluate nutrient and C dynamics, yield, and soil quality via Soil Management Assessment Framework (SMAF) following 15 years of continuous management under corn (Zea mays L.) (2008-2018) and soybean (Glycine max [L.] Merr.) (2019-2022) on a Dundee silt loam soil. After 15 years, mean soil organic C (SOC) stocks (0-30 cm depth) under NT were 25% higher than conventional tillage (CT). Between 2020-2022, SOC stocks increased 3 Mg ha-1 under NT and decreased 2 Mg ha-1 under CT. Increased SOC retention under NT could represent an opportunity for increasing the systems’ profitability as C markets expand. Greater SOC and aggregation resulted in greater SMAF soil quality index (SQI) under NT (71%), underscoring the critical role of organic matter in soil functioning in managed agrosystems. Yields were however unaffected by tillage (p > 0.05) and were not linked to SQI. The lack of relationship between SMAF SQI and yields suggest current scoring functions need revision, or that crop yields are affected by other edaphic and non-edaphic factors. SMAF illustrated positive impacts of NT on SOC sequestration and soil health, which may foster its adoption as a conservation practice in the lower Mississippi Delta. Overall, with soybean yields similar to CT, NT stands as a climate-smart management practice that allows for sustainable intensification in humid subtropical regions.