Spatial Distribution, Fractionation and Mobility of Soil Iron under Contrasting Cropping Systems in Indo-Gangetic Plain

Available iron (Fe) deficiency is prevalent issue in the Indo-Gangetic plain particularly in the areas with higher pH levels, lower organic carbon content and high concentration of calcium carbonate in the soil causing significant impact on agriculture production. To improve Fe availability, it is necessary to comprehend the relationship between Fe fractions in soil, its availability and their responses to different cropping systems: rice-wheat (RW) and legume-wheat (LW). Surface soil samples (0–15 cm) were collected from agriculture fields with different cropping systems rice-wheat and legume-wheat of Indo-Gangetic plain and were analysed for different soil iron fractions in the laboratory by the Tessier method. Soil properties such as pH, organic carbon, electrical conductivity, nitrogen, phosphorus, and potassium and CaCO3 were also measured. The mean Fe fractions in soil samples were found in the following order: Residual Fe > Manganese oxide-bound > Organic bound Fe (Org–Fe) > Carbonate bound Fe > Exchangeable Fe (Ex–Fe). LW cropping system significantly restores Ex–Fe and Org–Fe by 11.5 and 55% over RW cropping system. Mobility factor in LW soils (0.0469%) was markedly higher than RW (0.0345%), indicating improved Fe availability. High Reduced Partitioning Index value >0.95 across both systems revealed iron strong binding to stable fractions. Prolonged cultivation of RW cropping system disturbs the soil iron dynamics. Legume integration enhances Fe bioavailability by lowering pH and organic matter stabilisation. Therefore, it is advised to change the cropping system from cereal-cereal to cereal-legume, use organic manures, and adopt sustainable soil management strategies to replenish the available Fe status in the Indo-Gangetic plain Fluvisol.