Effects Of Different Water-upland Rotation On The Remediation Of Cadmium-contaminated Soils

Paddy-upland rotation is a kind of planting pattern which alternates rice and upland crop in sequence on the same field.This rotation is of great significance in improving soil physical and chemical properties,soil fertility and fertilizer efficiency of paddy field,it is also the traditional farming method in my country.In order to study the change of physical and chemical properties of soil,availability of Cd,accumulation and transportation of cadmium in crops and the effect on the absorption and accumulation of cadmium in rice under different cropping systems,study on the remediation potential of different paddy-upland rotation.We used a paddy-upland-paddy rotation system,Rice selected Xiangwanxian No.13 and Tianyouhuazhan,In winter dryland,we selected chicory,flax and two varieties of rape(Lvsheng No.1and Zhongyouza 19),planting another season of the same variety of rice in the second year,and a three-season field experiment was conducted in Jiaoxi town,Liuyang,Changsha city.The results showed that the concentration of Cd,the bioconcentration factor values and the transfer factor values of the aerial parts in the first-season rice tissues of Tianyouhuazhan were all higher than that of Xiangwanxian 13 in the experimental soil of total Cd 0.88 mg/kg and p H 5.8.In the treatment of different dryland crops in the second season,the Cd accumulation ability was ranked as Chicory> Flax>Lvsheng No.1> Zhongyouza No.17.Chicory is a kind of crop with the strongest ability to accumulate Cd.The Cd concentration of the aerial parts of chicory mowed four times was in the range of 15.73-24.47mg/kg,and the corresponding bioconcentration factor values was 14.98-30.97.The Cd content of Lvsheng No.1 rape leaves was the highest,above 4.0 mg/kg,and the corresponding BCF value was also the highest among several parts.The parts with the highest Cd concentration in Zhongyouza rape were stems,which reached 3.32 and 2.84 mg/kg,respectively.Flax is also a winter crop with a strong ability to accumulate Cd.The Cd concentration of flax leaves is above 7.77 mg/kg,respectively.The Cd concentration of the fruit parts of flax(including the shell and seeds)is above 3 mg/kg,and the corresponding BCF value ranges from 3.86 to 5.83.The results of the third harvest of rice showed that the accumulation of Cd in rice could be effectively reduced by planting different dry land crops,the bioconcentration factor and transport factor of rice decreased gradually from stem and leaf to brown rice.Among several rotation systems,rice-chicoryrice rotation and rice-flax-rice rotation have very strong ability to accumulate Cd.The two rotation systems can take more than 190 g/ha and 140 g/ha away from the soil respectively after planting,and the corresponding total extraction efficiency is more than 9% and 6% respectively.After planting different varieties of rice,except chicory treatment,the soil p H of rice decreased slightly after planting dry land crops.In addition to flax treatment,the Cd availability of paddy soil after rotation of several dryland crops was higher than that of CK.The stability of rice aggregates was lower than that of dryland crops,which may be due to the fact that the macroaggregates were subdivided into smaller aggregates.The same planting of different dryland crops effectively reduced the Eh value of paddy soil.The effect of different previous crops on Rice root morphology is not very great,and the difference of rice root morphology may be more related to the difference of rice varieties.