Regulation of As and Cd accumulation in rice by simultaneous application of lime or gypsum with Si-rich materials

Calcium (Ca) and silicon (Si) have been found to reduce inorganic pollutant accumulation by agricultural plants. Arsenic (As) and cadmium (Cd) are the most common and dangerous inorganic pollutants in cultivated soil that often present simultaneously. Due to difference in chemical properties of As and Cd, concurrent minimizing their uptake poses a problem. The effect of two types of Si fertilizers and Si-treated metallurgical slag applied with or without limestone or gypsum on the As and Cd accumulation by rice was investigated in medium-polluted paddy soils in field test. Application of Ca- and Si-rich substances reduced the grain As by 16 to 68% and the grain Cd by 30 to 56% with increasing yield by 16.6 to 31.0%. The root-to-grain transport of As and Cd depended on the plant-available Si supply in the soil. Soil-applied Si resulted in diminished As and Cd translocation inside plant tissue and decreased the pollutant mobility in the soil. The combination of Ca- and Si-rich substances reinforced the reduction in both the pollutant mobility in soil and accumulation by rice grain. Silicon-rich materials mainly impacted both As and Cd translocation into the grain, whereas Ca-rich substances demonstrated a more remarkable effect on the pollutant mobility in the soil. Limestone showed a higher decrease in the mobility of Cd, while gypsum was more efficient in the case of As. Thus, for minimizing pollutant accumulation by rice grain, the combination of Si fertilizer with limestone or gypsum could be recommended in the co-contaminated soil with prevailing Cd or As, respectively.