Study On Adjustment Of Planting Pattern Of Vegetable Soils Contaminated By Cadmium In Acid Zone

Field experiments were conducted in a vegetable land with an elevated cadmium(Cd)concentration in the soil of Xiangtan county,Hunan province.The food safety problems of vegetable planted in area contaminated by Cd in the south of China were investigated.Different planting techniques were used,such as the selection of low Cd-accumulating varieties,agricultural inputs detection,regulation of agronomic measures and substitute planting to ensure the food safety of locally produced vegetable.As a result,an appropriate technology for safe production of vegetable in acidic Cd-polluted farmland was proposed,which provided a technical reference for the adjustment of planting structure on acidic Cd-polluted vegetable-growing land in southern China.The main findings were as follows:(1)It was recommended to plant vegetables with low Cd accumulation,such as flowering stalk,Chinese cabbage,romaine lettuce,water spinach,potherb mustard,leek,onion,sweet potato,lettuce,white radish,ginger,balsam pear,towel gourd,muskmelon,pepper and cowpea,hyacinth bean,kidney bean in low Cd-polluted vegetable land.(2)The application of 4 500 kg·ha-1 CaC03 or 3 000 kg·ha-1 CaO in moderate(0.72±0.16 mg·kg-1)and severe(1.06±0.08 mg·kg-·)Cd-polluted vegetable land had the advantages of low dosage,low cost,significant effect and little secondary pollution.However,the effects of application of CaC03 or CaO in Cd-polluted vegetable land can only be maintained for one year.Compared with the control,the application of 4 500,6 000,7 500 kg·ha-1 commercial organic fertilizer had no obvious effect in severe Cd-polluted vegetable land.(3)Low Cd-accumulated vegetables,such as flowering stalk,Chinese cabbage,onion,white radish,balsam pear,towel gourd,muskmelon,cowpea,hyacinth bean,kidney bean,can be safely planted in the acidic moderate Cd contaminated vegetable land.In contrast,4500 kg·ha-1 CaCO3 or 3 000 kg-ha-1 CaO was required to reduce the Cd concentration in other vegetables,such as coriander and celery.Moreover,low Cd-accumulated vegetables such as onion,balsam pear,towel gourd,white radish,cowpea,hyacinth bean,kidney bean,can be safely planted in acidic severe Cd-polluted vegetable land and 4 500 kg·ha-1 CaCO3 or 3 000 kg·ha-1 CaO can be applied to further reduce Cd concentration in the edible part of vegetable.(4)In the acidic vegetable land with an average Cd concentration of 12.5 mg·kg-1,substitute planting trials were carried out by planting trichosanthes kirilowii and kiwifruit,and the result showed the Cd concentration of the trichosanthes kirilowii seed,trichosanthes kirilowii and kiwifruit were 0.1 mg·kg-1,0.12 mg·kg-1 and 0.11 mg·kg-1,respectively,which exceeded the Chinese maximum permissible limits for Cd and should not be promoted.However,non-edible hemp crops showed a positive growth potential,as compared to the control.It had certain promotion feasibility.In Xiangtan county,Hunan province,remediation and substitute planting trails were carried out in acidic vegetable land with varying degree of Cd contamination.As a result,the appropriate technology for the adjustment of planting structure in the acidic Cd-polluted farmland based on soil-vegetable pollution levels;"clean agricultural inputs+CaCO3 or CaO+low Cd vegetables+ substitute plantings" was established.The feasible mitigation strategies could be applied to reduce the trophic transfer of Cd from contaminated vegetable to local population.