Safe Utilization Of Slightly Cadmium-polluted Farmland Based On Cultivar Screening And In-situ Immobilization

Cadmium(Cd)contamination in agricultural soils has lead to serious food security issues due to the intensive agriculture and industrial development in our country.In order to achieve the safe utilization of slightly cadmium-polluted farmland and ensure food safety,three typical areas(from Shaoxing,Hangzhou and Wenzhou,respectively)with different levels of cadmium pollution in Zhejiang province were selected in this study.Through the screening of low-cadmium accumulation crop cultivars(rice,wheat,oilseed rape,maize),in-situ immobilization and the compound amendments combined with the water management,we obtained the best safe utilization technology in slightly cadmium-polluted farmland soil.The mean total cadmium and mean available cadmium contentration in the soils were Shaoxing > Hangzhou > Wenzhou.The soil in Hangzhou and Wenzhou was acidic,while the soil in Shaoxing was neutral.The main results are as follows:(1)The screening of low-cadmium accumulation crop varieties results indicated that cadmium concentrations in the different crops were significantly different,which was rice > wheat ? oilseed rape > maize.The rice cultivars with low grain Cd concentration were Xiushui519,Yongyou4953,which are recommended as suitable cultivars for planting in slightly cadmium-polluted farmland.Moreover,Yongyou4953 had a higher yield,which was the best rice cultivars for safe utilization.As for Cd accumulation,hybrid cultivars was significantly higher than the conventional ones,and japonica rice grain was significantly lower than indica rice.Besides,we found that the environmental effect was more important than the wheat cultivar effect in the variation of Cd concentrations.In the screening of oilseed rape varieties experiments,Yuyou 1402 gained the lowest grain Cd accumulation.For maize grain,the Cd accumulation was 0.007?0.026 mg/kg,TF(translocation factor)was 0.030?0.046,and Shengketian 88 had the lowest Cd accumulation in grain.All above results indicated that screening for stably low Cd accumulation and high yield crop cultivars was one of the most feasible and effective approaches to ensure food safety and quality.(2)The in-situ immobilization results indicated that different passivators significantly increase soil p H,which was hydroxyapatite > calcium magnesium phosphate > biochar.Moreover,and the addition of passivators played a decisive role in the transfer of Cd from soil to plant grain by reducing available cadmium.The two-years in-situ immobilization by passivators significantly reduced the DTPA-extracted Cd in the soil,and the crop yield significantly increased in the second year.Compared with the control,application of 1000 kg/mu biochar was the best treatment which significantly reduced 48.22%,32.35%,33.87%,18.19% of grain Cd accumulation during the four experiment in two years,respectively.In addition,the application of 500 kg/mu hydroxyapatite and calcium magnesium phosphate significantly reduced Cd accumulation in grain.(3)The uptake of cadmium by rice plant from soil was reduced significantly by the combinzation of amendments and deep irrigation compared with the solely treatment.Compared with the control,the contents of cadmium in the grain treated with calcium magnesium phosphate-palygorskite-sulfur powder + deep irrigation and limestone-zeolite-sulfur powder + deep irrigation were reduced by 56.53% and 55.53%,respectively.Deep irrigation could enhance the soil reduction effect and the formation of cadmium sulfide,achieveing the purpose of reducing the uptake of cadmium from soil by dilution effect.Above result suggested that application of amendments combined with deep irrigation was a convenient and effective technique to control cadmium up take of rice plant from soil.