The Passivation Effect on Cd of Mixing of Hyperaccumulated Plant Straw and Phosphate Rock Powder in Cd Polluted Soil

Soil culture experiments were carried out to study the effects of the mixture of cadmium (Cd) hyperaccumulator straw (Solanum nigrum L., Amaranthus chinense L., and Siegesbeckia orientalis L.) and phosphate rock on soil pH, available Cd content and soil nutrients in Cd polluted soil. The results showed that: (1) The soil pH was increased to a certain extent by three kinds of compound materials. (2) The contents of available potassium (AK) and available phosphorus (AP) in soil were increased to a certain extent by the three compounding materials, but there was no significant effect on total nitrogen (TN). And 2% phosphate rock powder and 1% Amaranthus chinense L. had the greatest increase in AP, reaching 49.28%, and 2% phosphate rock powder and 1% Siegesbeckia orientalis L. had the greatest increase in AK, reaching 136.23%. (3) The available Cd content in soil was reduced by three kinds of compound materials. The decrease of available Cd was the greatest in 2% phosphate rock powder and 1% Solanum nigrum L. straw mixed, which was 12.71%. In summary, the combination of Cd hyperaccumulator straw and phosphate rock powder can effectively passivate Cd in soil and improve soil nutrient content, and 2% phosphate rock powder and 1% Solanum nigrum L. straw are the best.