Of Soil Physicochemical Characteristics Of Farmland Using Different Tailings For Reclamation In Western Liaoning Province

There are rich iron ore resources in western Liaoning province.Long-term iron ore mining and beneficiation as well as large amount of iron ore tailings stacking have caused land damage and ecological environment destruction.According to the policy requirements of national mine reclamation and ecological restoration,the damaged land is usually reclaimed while mining.In the process of reclamation,due to the limitation of available soil resources,some mines try to use iron ore tailings and soil composite construction of soil profile technology.According to the investigation,the crop yield of reclaimed farmland is different due to the different technology and ratio of composite structure soil profile of iron ore tailings and soil.At present,the influence of soil profile constructed by iron ore tailings on the physical and chemical characteristics of surface soil in western Liaoning is not clear,and it remains to be studied which composite soil profile constructed by iron ore tailings and soil has better technological effect.Based on this,this study took the reclaimed farmland with iron tailings structure in western Liaoning as the research object.Through field investigation,two main profile structures(cinnamon soil 30 cm+ iron tailings 20 cm+ bottom soil 20 cm;The soil physical and chemical characteristics of 0-10 cm,10-20 cm,20-30 cm soil were measured,and the influence of profile structure on the soil of reclaimed iron ore tailings farmland was explored.In addition,the effects of different reclamation years(3 years,5 years,10 years)on the physical and chemical properties of surface soil were analyzed,and the temporal and spatial variation of reclaimed soil was discussed.The main results are as follows:(1)The subsoil layer is an important layer of soil profile suitable for crop growth.Soil organic matter was 4.72-6.26 g/kg in the farmland with a soil profile of 30 cm brown soil + 20 cm iron tailings + 20 cm bottom layer and 30 cm brown soil + 20 cm iron tailings.The soil available nitrogen content was 39.53-46.37 mg/kg,and the soil available phosphorus content was 2.85-5.94 mg/kg.The soil carbon,nitrogen and phosphorus contents were significantly higher than those of the farmland without 20 cm soil layer,and the maize yield was 9.29 t/ha,1.19 times(7.82 t/ha)of the latter.Therefore,laying 20 cm bottom layer is beneficial to soil nutrient accumulation and crop growth.(2)With the increase of reclamation years,soil bulk density showed a decreasing trend,and soil carbon and nitrogen content increased year by year.Under the influence of tillage and other agricultural measures,the soil bulk density of reclaimed farmland varied from 1.51g/cm3 to 1.74 g/cm3 in 10 years,and there was no significant difference between reclaimed farmland and normal farmland.Soil organic matter content was 6.69～7.39 g/kg,and soil alkali-hydrolyzable nitrogen content was 34.11～36.67 mg/kg,significantly increased by147.16%,211.21%,277.97%,74.95%,71.14%,125.45% compared with the initial reclamation.(3)Covering 30 cm soil on 20 cm iron ore tailings can meet the land reclamation quality requirements.There was no significant difference in soil water content and available P content between the farmland covered with 30 cm soil for 5 years and the farmland covered with 50 cm soil for 10 years,and the soil available K content of the former was significantly higher than that of the latter.There was no significant difference in soil organic matter and alkali-hydrolyzable nitrogen content between the two soil samples at 0-10 cm.Therefore,in western Liaoning province,where soil source is scarce,covering 30 cm soil on 20 cm iron ore tailings is the soil thickness required to ensure the normal growth and development of crops.The results showed that the farmland filled with iron ore tailings recovered well after long-term cultivation,and all physical and chemical indexes were close to the normal farmland in the region.This study fully verified the feasibility of using iron tailings structure to reclaim farmland soil from the theoretical level.In addition,the research results can be applied to the optimization of the profile structure scheme of reclaimed farmland in western Liaoning,and provide theoretical basis and scientific support for the reclamation of abandoned mining land and the utilization of iron tailings resources in the future.