Impact of Chelated Iron and Zinc Application Methods on Soil Properties and Micronutrient Availability during Rice Growth Stages

Zn and Fe are the most limiting nutrients for plant development and metabolism. This study evaluated the impact of Fe and Zn supplementation alternate methods such as biopriming, nutripriming, foliar and basal application. A randomized block design with 10 treatments under a rice system including RDF alone (T10), and combinations of iron (Fe) or zinc (Zn) or both applied through basal application, bio-priming, nutripriming, and foliar spray: T1–Fe (basal + foliar), T2–Fe (bio-priming + nutripriming), T3–Fe (basal + bio-priming + nutripriming), T4–Zn (basal + foliar), T5–Zn (bio-priming + nutripriming), T6–Zn (basal + bio-priming + nutripriming), T7–Fe+Zn (basal + foliar), T8–Fe+Zn (bio-priming + nutripriming), and T9–Fe+Zn (basal + bio-priming + nutripriming).This study evaluated the influence of different iron (Fe) and zinc (Zn) management strategies on soil chemical properties and the availability of DTPA-extractable Fe and Zn at critical growth stages of rice under a rice-based cropping system. Treatments involved sole and combined applications of Fe and Zn via basal, foliar, biopriming, and nutripriming methods. Soil chemical properties, including pH, electrical conductivity (ECe), oxidizable carbon, cation exchange capacity (CEC), and macronutrients (N, P, K), showed no statistically significant variation across treatments, although numerical differences were observed. The combined application of Fe and Zn (T9: basal + nutripriming + biopriming) consistently resulted in the highest DTPA-Fe and Zn concentrations across tillering, flowering, and post-harvest stages. DTPA-Fe ranged from 20.46 to 29.99 mg kg⁻¹ at tillering, while DTPA-Zn ranged from 0.77 to 1.47 mg kg⁻¹. A general declining trend was observed for both nutrients as the crop progressed. Results affirm that integrated micronutrient application enhances soil Fe and Zn bioavailability, demonstrating the potential of agronomic biofortification strategies to address micronutrient deficiencies in rice-based systems.