| In order to explore the application value of biochar to the same parent material soil in different planting years soils,corn stalk biochar was used as the soil amendment,the study selected granite parent material soil of two planting years(soil A,planting years>200a;soil B,planting years about 6a).The effects of four biochar treatments(mass ratio of biochar to soil:0.0%,0.1%,0.2%and 0.4%,respectively)on soil properties,rice yield and Cd uptake and accumulation of rice in two planting years soils were investigated by field experiments.The main test results were as follows:(1)Under CK treatment,there were differences in the physical and chemical properties of the soil between the two planting years soils.The pH value of soil A was 0.22 unit lower than that of soil B,and the contents of OM,CEC,total Cd,calcium chloride extracted Cd(CaCl2-Cd),alkali-hydrolysed nitrogen and available phosphorus in soil A were 1.82,1.26,8.29,3.52,1.23 and 2.53 times of those in soil B,respectively.The ratio of available Cd and the content of available potassium in soil B were 2.38 and 2.63 times of that in soil A.There was no difference in mechanical composition between soil A and soil B.Under the condition of biochar application(0.1%～0.4%),there were differences in soil properties between the two planting years soils.Compared with CK,the OM content of soil A increased by 5.99%～9.24%,the CEC content of soil B increased by 8.57%～30.93%(p<0.05),and the alkaline hydrolytic nitrogen content of soil A and B increased by 16.51%～37.48%and 2.42%～9.84%,respectively.The content of available K in soil A increased by 1.83%～26.92%,and the content of available P in soil B decreased by 34.23%～45.50%.There were no significant differences between biochar application and CK treatment for soil pH value,total Cd content,CaCl2-Cd content,the ratio of available Cd,clay,sand and silt contents in two planting years soils(p>0.05).(2)The application of biochar could increase the rice yield of the two planting years in different degrees,the rice yield of soil A increased by 6.31%-8.57%and that of soil B increased by 7.79%～18.49%at the rate of 0.1%～0.4%biochar application,and in the same conditions,the rice yield of soil A was much higher than that of soil B,and the increase of rice yield in soil B was basically higher than that in soil A.(3)Under CK treatment,there were differences in the accumulation and transport of Cd in different parts of rice(root,stem and leaf,rice husk and brown rice)in two planting years soils.The Cd enrichment coefficient of rice root(BCFroot)and the Cd enrichment coefficient of brown rice(BCFbrown rice)in soil A were 2.23 and 1.33 times that of soil B,respectively.There were differences in the Cd accumulation and transport in different parts of rice in two planting years soils under the condition of biochar application(0.1%～0.4%).Compared with CK,biochar application of 0.1%～0.4%had no significant effect on Cd content in rice parts in soil A(p>0.05),and the Cd content of brown rice in soil B decreased by 14.71%～62.75%.The BCFroot in soil A increased by 21.44%～99.58%,while the BCFbrown rice in soil B decreased by 12.24%～63.27%under the treatment of 0.1%～0.4%biochar;The TFbrown rice/root in soil A decreased by 20.00%-53.33%,The TFbrown rice/stem and leaf、TFrice husk/stem and leaf and TFbrown rice/root in Soil B decreased by 20.00%～53.33%,15.15%～63.64%,and 25.00%～62.50%,respectively,under biochar application of 0.1%～0.4%.(4)RDA analysis showed that the enrichment coefficient of brown rice(BCFbrown rice)in soil A was positively correlated with the proportion of available Cd in soil,and that wsa negatively correlated with soil pH value,total Cd content and clay content,while there were no significant differences among the amount of biochar application on the above indexes(p>0.05).Therefore,the biochar application of 0.1%～0.4%had no significant effect on the BCFbrown rice of rice in soil A.BCFbrown rice in soil B was positively correlated with the proportion of available Cd,the content of CaCl2-Cd and the content of available P,and negatively correlated with the content of CEC in soil.The biochar application of 0.1%～0.4%reduced the available Cd proportion and available P content of soil B,and increased the CEC content.Under the comprehensive action of these factors,the accumulation of Cd in soil for brown rice was reduced.(5)The biochar application of 0.1%～0.4%could increase the yield of rice to a certain extent,and affect the migration and transport of Cd from rice to soil.Under the same carbon planting conditions,biochar had a better effect on rice yield increase in soils with shorter cultivation years,but had no significant effect on rice enrichment and Cd transport in soils with longer planting years(p>0.05). |
