27-10 Soil Type and Irrigation Regime Influence Arsenic, Redox Conditions, and Micronutrient Cycling in Growth Chamber Rice Paddy Experiments

Session: Environmental Geochemistry and Health (Posters)

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Abstract:

Rice (Oryza sativa) is a globally critical food crop, but continuous flooding in paddy systems promotes the accumulation of toxic elements—particularly arsenic (As)—and alters the availability of key micronutrients (Fe, Mn, Zn, Mg, Cu, Cd). Alternate Wetting and Drying (AWD), an irrigation strategy that periodically drains paddies, can reduce As uptake and conserve water. However, the effectiveness of AWD varies with soil geochemistry, and its impact on As speciation and micronutrient dynamics is not fully understood.

To investigate these interactions, we conducted a growth chamber experiment using two contrasting rice paddy soils: a clay loam from Arkansas and a silty clay loam from New York. The Cocodrie cultivar—previously used in related field studies—was planted using both direct-seeding and pre-germinated transplanting methods under flooded and AWD conditions. Weekly porewater sampling throughout the growing season tracked temporal trends in As and micronutrients, while rice grain digestions quantified total elemental concentrations. Arsenic speciation (via HPLC-ICP-MS) will be used to distinguish inorganic and methylated As species in both porewater and grain.

Preliminary results show that both soil type and irrigation regime significantly influence porewater chemistry. AWD reduced grain As concentrations and improved micronutrient availability—especially in the silty clay loam soil. Ongoing speciation analysis will clarify how redox fluctuations affect the mobility and transformation of As. These findings support the refinement of AWD strategies that reduce contaminant risk without compromising grain nutrition.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-10260

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