Effects of Calcium Magnesium Hydrotalcite Application Rate on Cadmium Accumulation and Transport Characteristics of Double-cropping Rice in Southern Hunan
In order to study the optimal application rate of calcium magnesium hydrotalcite in double-cropping rice fields with mild cadmium pollution,the early rice varieties Luliangyou 996 and Zhuliangyou 819 and the late rice varieties Xiangwanxian 13 and Yuzhenxiang were used as test materials and a field trial was carried out in 2020 in lightly cadmium-contaminated rice fields(0.3 mg/kg＜total soil cadmium content＜0.6 mg/kg)in Hengyang County,Hunan Province to compare the cadmium uptake,accumulation,translocation and distribution in rice under different application rate treatments of calcium magnesium hydrotalcite(0 kg/hm2,M1;basic fertilizer for early rice 1 500 kg/hm2,M2;basic fertilizer for early rice 2 250 kg/hm2,M3;basic fertilizer for early rice 3 000 kg/hm2,M4).The results showed that the application of calcium magnesium hydrotalcite reduced the available cadmium content in the soil.The available cadmium content in the soil of each variety showed a trend of M1＞M2＞M3＞M4,and the soil available cadmium content of low cadmium accumulation varieties(Zhuliangyou 819 and Xiangwanxian 13)was generally higher than that of high cadmium accumulation varieties(Luliangyou 996 and Yuzhenxiang).The application of calcium magnesium hydrotalcite significantly reduced the cadmium content and accumulation in various parts of rice,and the cadmium content and accumulation decreased with the increase in the application amount of calcium magnesium hydrotalcite.The cadmium content and accumulation in each part of low cadmium accumulation varieties were lower than those of high cadmium accumulation varieties.The application of calcium magnesium hydrotalcite significantly reduced the cadmium enrichment coefficient in various parts of rice,but had not a significant effect on the cadmium transfer coefficient and distribution coefficient in various parts of rice.Considering the significance of the difference in cadmium content and accumulation in rice,the reduction effect and the economic benefit among different calcium magnesium hydrotalcite application rates,it is more appropriate to select low cadmium accumulation varieties and base application of calcium magnesium hydrotalcite at 2 250 kg/hm2 in rice fields with mild cadmium pollution in southern Hunan.
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