Attenuated cadmium and arsenic enrichment in rice by co-application of organic composting and chemical fertilization

A pot experiment was conducted on arsenic (As) and cadmium (Cd) co-contaminated soil to discern the influence of varying proportions of pig manure compost (PM) vis-à-vis chemical fertilizers (NPK) on the mitigation of Cd and As absorption by rice. Our findings illustrated that by increasing the PM proportions from 25 to 100%, it manifested a statistically significant reduction in the mobilized fractions of Cd, accounting for up to 77% reduction in soil CaCl₂-Cd concentrations. Conversely, the NaHCO₃-As reactions were contingent on the distinct PM application rates. Furthermore, augmented PM application rates correlated with a substantial surge in Cd and As concentrations within the iron (Fe) and manganese (Mn) plaques, ranging from up to 116.6% and 85.9%, respectively. This led to a concomitant decline in Cd and As concentrations within the grains, up to 72.6% and 74.5%, respectively. Notably, grain concentrations of As and Cd diminished progressively with increased PM application, reaching a nadir with the 75% PM treatment. In summary, the observed mitigation in contamination is postulated to stem from the modulation of soil attributes via PM addition, which curtails Cd availability, combined with the bolstered immobilization of As and Cd by the Fe/Mn plaques.