Abstract:

This study aims to provide theoretical guidance for the safe production of chili in central Guizhou and screen out passivators with better effect in areas with moderate cadmium pollution. Two kinds of carbon-based passivators (coconut-shell biochar and activated carbon) and two kinds of silicate passivators (silica-calcium fertilizer and sepiolite) were selected to carry out field plot experiments. In the experimental design, passivators were added alone or carbon-based passivators were mixed with silicate passivators, and the total amount of application was 3000 kg/hm². The results showed that the single application of silicon-calcium had the most significant effect on increasing soil pH, which was increased by 2.36 units compared with that of CK. Under the treatments of mixed application of passivators, the most significant treatment for increasing soil pH was activated carbon + sepiolite, which increased soil pH by 2.07 units. The application of silicon-calcium alone had the best effect on reducing the content of DTPA-Cd in soil, and the reduction rate was 36.5%. Coconut-shell biochar + silicon-calcium had the best effect on reducing the content of DTPA-Cd in the soil among the mixed application of passivators, and the reduction rate was 28.5%. Sepiolite alone could significantly reduce the enrichment coefficient of Cd in chili, and the content of Cd in chili was significantly reduced by 47.4%, which could minimize the safety risk in edible parts of chili. It is suggested that carbon-based passivators and silicate passivators should be applied separately or at different time in areas with moderate Cd contamination, which could not only effectively reduce the contamination risk of Cd in soil and crops, but also maximize soil improvement and enhance the passivation efficiency of passivators.

Key words: carbon-based passivator, silicate passivator, cadmium, chili, passivation, safety risk