Co-application of earthworms and arbuscular mycorrhizal fungi enhances arsenic tolerance of upland rice and improves soil health

Abstract

Earthworms and arbuscular mycorrhizal fungi (AMF) are essential soil organisms that interactively shape soil-plant dynamics. This study elucidates the mechanistic basis of their co-inoculation in enhancing arsenic (As) tolerance in upland rice (Oryza sativa L.) and improving soil health in a pot experiment with As-contaminated soil (250.18 mg kg⁻¹). This study revealed that the inoculation effects of co-inoculation on rice biomass, N uptake, and P uptake were 86 %, 109 %, and 177 %, respectively, while reducing As concentration in shoot by 38 %. Physiological analyses revealed a 40.17 % reduction in malondialdehyde (MDA) content and a 6 % increase in superoxide dismutase (SOD) activity, indicating enhanced antioxidant capacity. Subcellular As compartmentalization shifted markedly, with organelle-bound As decreasing by 27 % (roots) and 48 % (leaves), while soluble fraction and cell wall sequestration increased. Soil health metrics improved, evidenced by elevated catalase (38 %), urease (15 %), and acid phosphatase (39 %) activities, alongside a 13 % reduction in bioavailable As fractions (As-F1 and As-F2) due to increased As-F4 stabilization. These findings demonstrate that earthworm-AMF synergy mitigates As toxicity by dual strategies: (1) enhancing plant antioxidant defenses and subcellular As compartmentalization, and (2) promoting plant growth via soil enzyme activation and nutrient cycling. This integrated approach offers a scalable, eco-sustainable strategy for safe rice cultivation in As-contaminated agroecosystems.