Exploring the mechanisms of organic fertilizers on Cd bioavailability in rice fields: Environmental behavior and effect factors
Jingbin Liu, Wentao Yang, Hang ZHOU, Muhammad Zia‐ur‐Rehman, Muhammad Abdus Salam, Linnan Ouyang, Yonglin Chen, Liyu Yang, Pan Wu
Abstract
The problem of paddy Cadmium (Cd) contamination is currently the focus of global research. Earlier researches have confirmed that utilization of organic fertilizers regulates Cd chemical fraction distribution by increases organic bound Cd. However, environmental behaviours of organic fertilizers in paddy are still lack exploration. Here, we critical reviewed previous publications and proposed a novel research concept to help us better understand it. Three potential impact pathways of utilization of organic fertilizers on the bioavailability of Cd are presented: (i) use of organic fertilizers changes soil physicochemical properties, which directly affects Cd bioavailability by changing chemical form of Cd(II); (ii) use of organic fertilizers increases soil nutrient content, which indirectly regulates Cd supply and bioaccumulation through ion adsorption and competition for ion-transport channels between nutrients and Cd; and (iii) use of organic fertilizers increases activity of microorganisms and efflux of rice root exudates, which indirectly affects Cd bioavailability of through complexation and sequestration of these organic materials with Cd. Meanwhile, dissolved organic matter (DOM) in the rhizosphere of rice is believed to be the key to revealing the effects of organic fertilizers on Cd. DOM is capable of adsorption and complexation-chelation reactions with Cd and the fractionation of Cd(II) is regulated by DOM. Molecular mass, chemical composition, major functional groups and reaction sequence of DOM determine the formation and solubilization of DOM-Cd complexes. • Soil pH, organic matter, and Eh are key factors directly affecting the availability of Cd. • Antagonism and competition between nutrients and Cd impact Cd uptake by rice. • Rhizosphere microbes and root exudates efflux indirectly affects the availability of Cd. • The influence of dissolved organic matter on Cd availability plays a key role.