Effects Of Different Application Methods Of Municipal Sludge On Soil And Maize Growth

With the continuous development of the social economy and the rapid increase of population,the amount of municipal sludge is increasing.How to safely dispose of and effectively use municipal sludge has become one of the major environmental problems that need to be studied and solved urgently.Municipal sludge as good plant availability and high agricultural value because of it is rich in organic matter and nutrients required by plants.From the aspects of economic development,comprehensive utilization of resources and urban ecological environment,land application of municipal sludge is an economical and sustainable way to dispose of sludge.In this paper,the sludge from the domestic sewage treatment plant in Tongchuan,Shaanxi Province was used as the main research object.Using maize as the experimental material,field experiments were conducted to study the different application methods?the furrow application,the spraying application,and the application of the sludge below the surface soil?and different dosages of sludge(30?90 and 200 t?hm^-2),to investigate the effects on nutrient and heavy metal contents in soil and growth and quality of maize.The main conclusions were as follows:1.The analysis of the basic physical and chemical properties and total amount of heavy metals of the tested sludge show that the nutrients such as organic matter,TN,TP and TK in the sludge are higher,and the total amount of heavy metals in the sludge basically meets the standard.After the sludge was applied to the farmland in three different ways,the contents of organic matter,TP,TK,ammonium nitrogen,nitrate nitrogen,available phosphorus and available potassium increased in different degrees.And the contents of Cu,Zn and Pb in the soil increased to different extents,but they did not exceed the limit values in the latest soil environmental quality standards in China.In the case of Cu,Zn and Pb content in different soil layers,heavy metals mainly accumulate in the 0²0 cm soil layer.2.After the sludge is applied to the farmland in three different ways,the effects on the growth and quality of the maize were different.For the furrow applicationthe,the emergence rate and grain yield of maize under the three dosages of sludge were lower than the control,while the biomass per plant was significantly higher than that of the control.The chlorophyll content of the leaves increased first and then decreased with the increase of sludge dosage,and reached the highest when the dosage was 90 t/hm²,the grain protein content increased with the increase of sludge dosage,and the highest content was when the dosage was was 200 t/hm²;For the spraying application,the emergence rate,plant height,biomass per plant and grain protein content of maize increased first and then decreased with the increase of sludge dosage,and reached the highest when the dosage was 30 t/hm²,the grain yield under this treatment increased by 25.63%compared with the control;For the application of the sludge below the surface soil,compared with the other two application methods,the emergence rate and grain yield were higher.The highest grain yield was 656.70 kg/667m² when the dosage was 30 t/hm²,which was 29.64%higher than the control.The biomass per plant and the total chlorophyll content of the leaves increased first and then decreased with the increase of sludge dosage and the protein content of grain increased with the increase of sludge dosage,and reached the highest when the dosage was 200 t/hm².3.After the sludge was applied to the farmland in three different ways,the content of Cu,Zn and Pb in the roots and leaves of the maize increased significantly with the increase of sludge dosage and the content of Cu and Zn in the grain also increased.However,the Pb content in the grain was not significantly different from the control.The distribution of Cu and Pb in various organs of maize was root>leaf>seed,and the distribution of Zn in various organs of maize was leaf>root>seed.The content of heavy metals in kernels in these test treatments were lower than the standard limit in the latest food contaminant limit standard in China,and the risk of exposure to the three heavy metals by residents through the edible corn route was small.In this research,it has the better impact and environmental effect when the sludge dosage was 30 t?hm^-2.In order to reduce the stress effect caused by the local accumulation of sludge in soil,the application of the sludge below the surface soil and the spraying application were relatively good ways.