In order to study the effects of different amounts of calcium and magnesium hydrotalcite on the soil characteristics of cadmium-contaminated rice fields

the yield of double cropping rice and the cadmium accumulation in rice

and to explore the best application mode of calcium and magnesium hydrotalcite in cadmium contaminated double cropping rice fields

in 2021

field experiments were conducted in the heavy cadmium contaminated rice fields (total cadmium content 1.16 mg/kg) in Liangtian Town

Chenzhou City

Hunan Province

using early rice varieties Xiangzaoxian 45 and Luliangyou 996

late rice varieties Chuang Liangyou 669 and Yuzhenxiang as experimental materials

The soil characteristics

yield components and cadmium accumulation of double cropping rice under four treatments of calcium magnesium hydrotalcite (0

CK; early rice basal application of 3 000 kg/hm2

T1; early rice basal application of 1 500 kg/hm2

T2; early rice basal application of 750 kg/hm2; late rice basal application of 750 kg/hm2

T3) were compared. The results showed that: (1) The application of calcium magnesium hydrotalcite could increase the soil pH and the contents of alkali hydrolyzable nitrogen

available potassium

and available phosphorus

respectively by 0~3.06%

4.30%~13.80%

6.67%~40.00%

and 25.53%~30.47% at the maturity of early rice

respectively

and 1.56%~4.07%

11.79%~14.50%

15.79%~31.58%

3.73%~17.17% at the maturity of late rice

showing a trend of T1 > T2 > T3. (2) Application of calcium and magnesium hydrotalcite could reduce the content of available cadmium in soil. The content of available cadmium in early and late rice ripening stages was reduced by 5.26%~42.86% and 18.19%~36.84% respectively

with a trend of T1 > T2 > T3. (3) The content of cadmium in brown rice and the accumulation of cadmium in the upper part of plant at maturity were the lowest in T1

the second in T2 and T3

and the highest in CK. The content of cadmium in Xiangzaoxian 45 decreased by 33.33%~44.44% and 4.89%~20.76% respectively

that in Luliangyou 996 decreased by 30.00%~60.00% and 6.00%~30.98% respectively

that in Yuzhixiang decreased by 27.78%~50.00% and 15.93%~34.07% respectively

and that in Chuang Liangyou 669 decreased by 26.67%~60.00% and 12.58%~28.56% respectively. (4) The yield of double cropping rice Xiangzaoxian 45

Chuang Liang You 669 and Yuzhen Xiang was the highest in T1

followed by T2 and T3

and the lowest was in CK; The yield of Luliangyou 996 was the highest in T2 treatment

the second in T1 and T3 treatment

and the lowest in CK treatment. Calcium magnesium hydrotalcite increased the yield of early and late rice by 4.11%~10.79% and 1.69%~11.29%

respectively. This experiment shows that the larger application amount of calcium magnesium hydrotalcite has a better effect on rice yield increase and cadmium reduction

but considering the significance of rice yield and cadmium content difference between treatments and the cost of calcium magnesium hydrotalcite

1 500 kg/hm2 calcium magnesium hydrotalcite is more appropriate under this experiment condition.