Iron release dynamics in Indo-Gangetic alluvial soils under variable moisture conditions: Insights from multi-model kinetic and geochemical speciation analysis.

Iron (Fe) plays a significant role in intensive cultivated soils such as alluvial soils of Indo-Gangetic Plains (IGP). However, it is often identified as deficient micronutrient because of its strong association with soil minerals and low solubility under aerobic and high-pH conditions, Fe is often unavailable to plants, despite its abundance in most soils. Investigating kinetic models along with geochemical model provide a valuable framework for understanding how any nutrient availability shifts over time along with its distribution. In the present investigation, an incubation experiment was carried out with soils of 20 different locations throughout the region at various moisture content to observe the temporal release pattern of Fe. The results indicate that both moisture status and incubation duration significantly influence 0.05 M Ca(NO3)2-extractable Fe in IGP soils. Soil properties such as pH and EC showed significant negative correlations with amount of Fe release, whereas CEC, clay content, moisture content, and field capacity exhibited significant positive relationships. Moisture plays a key role in regulating redox-driven dissolution and reprecipitation of Fe, while incubation time promotes aging and stabilization of Fe minerals in these soils.