Pig manure-derived DOM enhances soil Cd adsorption to reduce Cd accumulation in rice organs

ABSTRACTSDissolved organic matter (DOM) has different functions that affect the absorption and resolution behavior of soil Cd. We investigated two exogenous DOM (pig manure and rice straw) in soils, analyzed their structural features, and explored their effect on Cd behavior in soil. Our results showed that the two exogenous DOM contain similar functional groups, including carboxylic acids, alcohols, alkanes, phenols, and polysaccharides. The molecular weight of DOM in F2 to F4 (3 kD-30 kD) have the effect of activating and migration of Cd. Pot and field experiments demonstrate that DOM from pig manure is more effective in enhancing soil Cd adsorption and reduces the exchangeable Cd in soil during the seedling stage of rice. Under the treatment of pig manure and straw, the Cd in the roots, stems and leaves of rice decreased by 14%, 11%, 10%, and 8%, 14%, 10%, respectively. It indicates that pig manure application reduces Cd accumulation in rice roots, and straw application reduces it in rice stems. Overall, after applying pig manure and rice straw, Cd concentration in rice grains decreased by 36% and 17%, respectively. This study is conducive to a further understanding the behavior and morphological changes of Cd in paddy soil.