Effects of different Yellow River sediment filling reclaimed soil profiles on the distribution of elements in soil and crops

The use of Yellow River sediment as filling material in the mining subsided area along Yellow River can not only provide sufficient and safe filling materials， but also play a certain role in the dredging of Yellow River. However，there are some problems such as insufficient cover soil，poor water and fertilizer conservation and low crop yield in the reclaimed land filled with Yellow River sediment. Therefore，it is necessary to carry out the research on the soil profile reconstruction technology and the migration and transformation of elements in different soil profiles of the reclaimed land filled with Yellow River sediment，so as to guide the reclamation process and subsequent farmland utili⁃ zation and management. Based on the characteristics of the traditional agricultural soil profile and the soil profile formed by the existing filling reclamation techniques，and the factors such as the thickness of surface cover soil， four different soil profile configurations were designed，including the 30 cm soil + 70 cm Yellow River sediment，the 50 cm soil + 50 cm Yellow River sediment，the 30 cm soil + 40 cm Yellow River sediment + 15 cm soil + 15 cm Yellow River sediment and the 50 cm soil + 40 cm Yellow River sediment + 10 cm soil. Through the indoor soil col⁃ umn corn cultivation experiment，during the growth of corn，the main nutrient elements such as nitrogen(N)，phosphor⁃ us(P)，potassium(K)were added by fertilizing on the column surface and some harmful heavy metal elements such as lead( Pb)， cadmium ( Cd)， arsenic ( As)， mercury ( Hg) and chromium ( Cr) were added by surface watering. After the growth of corn，the soil samples were collected from the surface of the soil column in 10 cm units，and the samples of corn plants were collected to test the contents of N，P，K，Pb，Cd，As，Hg and Cr. It is found that the profile of the same surface soil thickness such as profile configuration 1 and 3， the distribution law of each element is similar. However，due to the addition of central interlayer in the profile configuration 3，which enhances the adsorption of elements，the retention of N and P is enhanced. In the profile configuration 2 and 4，although the overall law of each element is similar，the configuration 4 increases the bottom layer of 10 cm soil layer，and the retention of N and P is enhanced. The distribution of K in all configurations is no regular. While heavy metals are adsorbed on the surface lay⁃ er，the law of heavy metals distribution of all configurations are same and the Cd migration is slightly stronger. Com⁃ pared with the profile configuration 1 and the profile configuration 2， the content of N and P nutrient elements in the maize plants of profile configuration 3 is relatively high. In terms of maintaining soil fertility and promoting plant growth，the profile configuration 3 has a great advantage. In the crop experiments，the increase of soil thickness is beneficial to the retention of N and P. The K is mainly absorbed by corn and is almost unretained in the soil. Heav⁃ y metals in maize are weakly absorbed and the pollution risk is low. The particle size distribution，pH，organic matter and mineral composition of the soil and Yellow River sediment are analyzed. Due to the larger particle size，lower pH， and lower organic matter content of Yellow River sediment，the lower content of clay minerals including chlorite and il⁃ lite，it is not conducive to the retention of elements. Thus，increasing the profile configuration of the middle sandwich soil layer is beneficial to the retention of fertility and moisture. However，due to the difficulty of the reclamation process，it is recommended to adopt the profile configuration 3(30 cm soil + 40 cm Yellow River sediment +15 cm soil +15 cm Yellow River sediment).