Effects Of Municipal Sludge On Rape Growth And Soil Phosphorus Availability

Land use is currently recognized as the most effective method for the utilization of sludge resources.However,heavy metals in sludge also enter the soil environment,which limits the use of sludge.The current literature on the impact of urban sludge on rapeseed and the impact of municipal sludge on soil phosphorus form content and conversion is less.Therefore,through the study of the impact of urban sludge on soil environment and plants,suitable parameters for sludge land use are proposed.It will help improve the utilization of sludge resources,reduce environmental pollution,and achieve sustainable development of the environment and resources.In this paper,urban sludge was used as a material,and short-term pot experiment and culture experiment were conducted to analyze the characteristics of plant growth and heavy metal content,soil nutrient content,phosphorus form and phosphatase activity by applying different proportions of sludge treatment,and to explore the urban sludge quality and soil quality.With regard to the effects of plant growth and transformation of phosphorus form,an appropriate measure and treatment method for urban sludge land use was put forward.Through the study:?1?The results of short-term pot experiment showed that when the sludge application rate was less than 60 t/hm²,the municipal sludge could significantly increase the content of organic matter,total nitrogen,alkali-hydrolyzable nitrogen,total phosphorus and available phosphorus in the soil and improve the soil fertility,plant growth provided sufficient nutrients,significantly promoted the growth of rapeseed,and significantly increased the biomass of rape grains,pods,straw,and roots.Municipal sludge can increase the content and proportion of available heavy metals such as As,Cd,Cu,Ni,Pb and Zn in the soil and increase the bioavailability of heavy metals,but the contents of heavy metals such as As,Cu,Ni,Pb and Zn in soil and rapeseed did not exceed the national quality standards.In addition to the enrichment coefficient of Zn on rapeseed grains greater than 1,the enrichment coefficients of As,Cr,Cu and Ni in other parts of oilseed rape did not reach 1.In addition to oilseed rapeseed meal,rapeseed kernels,straw and roots showed a consistent accumulation of heavy metals such as Zn,Cu,Ni,Cr and As,followed the order of Zn>Cu>Ni>Cr>As>Cd>Pb.?2?The results of culture experiments showed that the municipal sludge added the phosphorus component in the soil,increased the total phosphorus,available phosphorus,inorganic phosphorus content and phosphatase activity,promoted the conversion of organic phosphorus to inorganic phosphorus,promoted the mineralization of phosphate monoester and pyrophosphate the hydrolysis of salt increases the availability of phosphorus in the soil.The contents of soil total phosphorus,available phosphorus and inorganic phosphorus all increased with the increase of sludge contents,and reached the highest when the application amount was 120 t/hm².At the initial stage of cultivation,phosphorus in the sludge gradually migrates to the soil,and the content and proportion of available phosphorus sources,mainly Ca₂-P and Ca₈-P,gradually increase.As time goes on,this is in turn converted to the slow phosphorus of Fe-P and Al-P.The content and proportion of inorganic phosphorus and phosphatase activity in soil increased with the increase of sludge amount,reached the highest level at the 30th day,and then showed a decreasing trend with the extension of culture time.