Research On Soil Fertility Improvement And Safe Utilization Of Reclaimed Construction Waste Abandoned Farmland

In recent years,a considerable amount of building trash generated during the urbanization process has carelessly encroached on high-quality farmland around the city,forcing it to be abandoned.When reclaiming abandoned farmland,issues such as poor soil quality,low soil fertility,and damage to soil fertility are frequently observed,all of which are insufficient to support the nutritional requirements of crop development.Under the"double reduction"policy,relying on the short-term large-scale application of chemical fertilizers to restore soil fertility has proven insufficient to meet the needs of green agricultural clean production.This study chose organic fertilizers and microbial fertilizers with a longer fertilizer effect period and milder soil environmental quality to improve the fertility of abandoned farmland soils reclaimed with construction residues in order to not only realize the reclamation of abandoned farmland with construction residues,but also meet agricultural green and clean production.Quality improvement is critical for achieving green and clean production as well as the safe exploitation of building slag waste lands.The experiment used a compound fertilizer control group(CK),three organic fertilizer treatments(OF),and three microbial bacterial fertilizer treatments(MF)to investigate the effects of different organic fertilizer and microbial bacterial fertilizer application amounts on reclaimed construction residue and abandoned farmland soil.The effect of different treatments on wheat yield soil fertility,and heavy metal health risks was analyzed.This study provided theoretical basis for fertilizer use and the improvement and safe utilization of abandoned farmland.The main findings are as follows:(1)The application of organic fertilizer and the application amount of microbial bacterial fertilizer with low addition ratio had no significant effect on soil p H.While soil organic matter,total nitrogen,alkali-hydrolyzed nitrogen,available phosphorus,available potassium,available iron,available manganese,available zinc.Available molybdenum increased with the increase of the application amount of organic fertilizer and microbial bacterial fertilizer,and the effect of microbial bacterial fertilizer on the soil properties was better than that of organic fertilizer.Among the organic fertilizer treatments,the organic fertilizer application rate of 22500 kg/hm~2had the best effect on the improvement of soil fertility.Among all treatments,the microbial fertilizer application rate of 30000 kg/hm~2had the best effect on the improvement of soil properties soil fertility,and the soil fertility index increased by 42.7%compared with the CK.(2)Both organic fertilizer and microbial fertilizer improved the physical quality of wheat grains and increased wheat yield.When the application rate of organic fertilizer was15,000 kg/hm~2,the effect of various physical indicators and yield of wheat in organic fertilizer treatment was better than that of microbial fertilizer treatment,while the difference was not significant.When the application rate was 22500 kg/hm~2and 30000 kg/hm~2,the effect of microbial bacterial fertilizer treatment on physical indicators and yield of wheat was significantly better than that of organic fertilizer treatment.In terms of nutritional quality,microbial fertilizer was more prominent in increasing the protein content of wheat.When the application rate of organic fertilizer was 15000 kg/hm~2,the contents of Ca and Mg in wheat were significantly increased;when the application rate of microbial bacterial fertilizer was 15000 kg/hm~2,the contents of Ca,Mg,Fe and Mn in wheat were significantly increased.When the microbial bacterial fertilizer application rate was 30000 kg/hm~2,the comprehensive improvement effect of wheat yield and quality was the best.(3)The content of heavy metals in soil under all treatments did not exceed the screening value of"Soil Environmental Quality Agricultural Land Soil Pollution Risk Management and Control Standard(Trial)"(GB15618-2018),and the Nemerow pollution index values were less than 0.7,which ware safety that can be used as agricultural production.With the increase of microbial fertilizer application,the content of Hg,As and Pb in the soil increased,indicating that microbial fertilizer application with long-term had potential risks of Hg pollution.Under the application rate of 15000 kg/hm~2,the contents of Cr,Pb,and Ni in wheat grains increased significantly in organic fertilizer treatment,and the contents of Hg,Cr,and Pb in wheat grains by microbial fertilizer increased significantly.The content of heavy metals gradually decreasd with increasing organic fertilizer addition.According to the results of health risk assessment,there was no health risk in heavy metals pollution in wheat,and the wheat of adult TTHQ index was acceptable(TTHQ≤1.0)except for the CK treatment.Compared with microbial bacterial fertilizer,organic fertilizer has better effect in reducing the accumulation of heavy metals in wheat grains.(4)The grey relational method was used to evaluate the comprehensive benefits of"wheat-soil"under different organic fertilizer applications.The best effect was obtained at30000 kg/hm~2,and its gray correlation was increased by 41.6%compared with CK treatment.To sum up,the application of organic fertilizer and microbial bacterial fertilizer in the abandoned farmland soil reclamation in the suburbs of Chengdu improved the soil fertility and soil quality,which also increased the yield and quality of wheat,and realized safe and green utilization of organic fertilizer and microbial bacterial fertilizer.Considering the improvement of soil fertility,farmland output and health risks,applying 30000 kg/hm~2of microbial bacterial fertilizer was recommended as the best solution for soil fertility improvement and safe utilization in the reclamation and construction slag abandoned farmland in the suburbs of Chengdu.