The Mechanism On Decreasing Cadmium In Rice By The Conditioner Containing Phosphorous

Cadmium pollution is an important problem in China’s agricultural environment,especially in the vast rice-growing areas in the south,there are a large number of soil and rice cadmium excessive situation,so it is of great significance to control the cadmium pollution farmland.In the prevention and treatment of cadmium pollution,considering that China has a large population and a serious food problem,it is impossible to stop food production on a large scale and carry out soil remediation.Therefore,the mode of managing while producing becomes the first choice.Agricultural regulation measures can be used to achieve safe grain production in cropland where cadmium exceeds the limit.In order to reduce the content of cadmium in rice,functional fertilizer was used as conditioner to regulate the physical and chemical properties of cadmium-polluted soil.Calcium magnesium phosphate fertilizer and quicklime were used as raw materials in this study,field trials have been arranged in Liuyang and other places,the key mechanism of adding functional fertilizer to reduce cadmium in rice was revealed by studying the physical and chemical properties of rice soil,biodiversity and iron film in rice roots.The main conclusions of this paper are as follows:1.After being treated with 0.5‰ and 1.0‰ conditioner,the cadmium content in rice decreased from 0.93 mg/kg to 0.08 mg/kg and 0.11 mg/kg respectively,and the cadmium content in rice reached the national food safety standard(<0.2 mg/kg).2.The increase of p H and P in soil is two important factors to reduce effective cadmium,Ca,Mg,Mn and Zn reduced the cadmium transport capacity of relative transporters in roots.After treatment,the concentration of Mn and Zn in roots increased by50-140% and 10-35% respectively,while the concentration of Cd decreased by 20-50%.3.Modulators increase biodiversity.Shannon index showed 0.5‰ and 1.0‰ increased species diversity(7.057 and 7.044),and CK and 0.2‰ was relatively low(6.858 and6.995).There was significant positive correlation between the abundance of Bacterodietes-vadin HA17,Syntrophaceae and Thiobacillus in the soil and P,Bryobacter and Candidatus Solibacter were significantly negatively correlated.These microbial abundance changes,especially the potential impact of Thiobacillus microbes on the bioavailability of Cd.4.Modulators can affect Cd enrichment of rice surface iron film.The results indicate that the increase of the dosage of conditioner,the effective Cd concentration in soil decreases,this results in a decrease in the amount of Cd adsorbed on the iron film,amount of cadmium that ends up in the white roots is also reduced.On the other hand modulators increase the enrichment ability of Zn and Mn in iron films,reducing Cd enrichment,competition between Zn and Mn and Cd over ion channels may be another reason for the lower concentration of Cd in white roots.