The effect of different formula of NPK and twice topdressings on rice growth in typical double cropping rice area, which located at Kaihui, Ganshan, Matang and Xinqiang towns, were studied on field experiment in order to select the formula of compound fertilizer and top dressing mode for double cropping of rice production in Hunan. The results showed that the optimized formulated fertilizer treatment, which increased the proportion of phosphorus and potassium and reduced its nitrogen fertilizer by 7.5 kg/hm2 can ensure early rice stable. Fpr example, the yield of late rice increased by 187.5-378.0 kg/hm2 compared with the conventional complex fertilizer （N-PO5-K2O formula of 20-10-10 for early rice and 26-10-13 for late rice）. The N-P2O5-K2O formula 18-14-16 of optimized formulated fertilizer which was suitable for early rice production, and the other N-P2O5-K2O formula 18- 9-16 was suitable for late rice production. The rice yields for top-dressing at tiller- ing stage and booting stage can increased by 187.5-382.5 and 258.0-415.5 kg/hm2 for eady and late rice and the nitrogen use efficiency advanced 10.9-24.2 percent- age points （31.5%-51.1%） for eady rice and 8.3-13.4 percentage points （36.2%- 64.9%） for late dce compared with the top-dressing at tillering stage.
To investigate the effects of Tianshifu soil conditioners on rice growth and their control effects on Cd absorption and accumulation in rice, a test was carded out in the field typically polluted by Cd in Hunan Province. The results showed that the Tianshifu soil conditioner, soil bacterial conditioner and the combination of Tian- shifu soil conditioner and soil bacterial conditioner all could promote rice growth, im- prove rice yield and reduce significantly Cd content in rice grains. In Beishan, the Cd contents in rice grains treated by Tianshifu soil conditioner, soil bacterial condi- tioner and the combination of Tianshifu soil conditioner and soil bacterial conditioner were reduced by 37.63% （P〈0.05）, 32.59% （P〈0.05） and 27.95% （P〈0.05） respec- tively compared with that in rice grains treated by conventional fertilization; In Xiang- tan, the Cd contents in rice grains were reduced by 54.36% （P〈0.05）, 50.19% （P〈 0.05） and 45.22% （P〈0.05） respectively. The rice grains harvested at the two test sites all met the national food safety standards. Considering the control effect on Cd contamination, Tianshifu soil conditioner 〉 combination of Tianshifu soil condi- tioner and soil bacterial conditioner 〉 Tianshifu soil bacterial conditioner. In addition to reducing Cd absorption in rice, as described in the lime application treatment, the application of Tianshifu soil conditioners also inhibited the transportation of Cd from rice straws to rice grains. The Tianshifu soil conditioner, soil bacterial conditioner and combination of Tianshifu soil conditioner and soil bacterial conditioner also effec- tively improved the soil acidity, increased the soil pH value and reduced soil avail- able Cd content to some extent.
