Effects On Ecosystem Of Biogas Slurry Substituting For Chemical Fertilizer On Rice And Wheat

Fertilizer is an important chain in the process of rice and wheat production.The application of fertilizer has experienced the changing process from organic fertilizer to chemical fertilizer.This process has profoundly changed the farmland ecosystem and brought many problems.The recovery efficiency and agronomic efficiency of chemical fertilizer was low.The long-term use of chemical fertilizer may bring many problems,such as soil acidity,soil consolidation,soil productivity decline and diminishing returns.Therefore,it is a new theme to reconstruct fertilizer input structure and seek alternative sources of fertilizer in terms of rice and wheat production.There was some foundation on the application of different types of organic fertilizer in agricultural production.However,the difference is obvious in different regions.Due to the characteristics of high water soluble nutrients,high utilization rate and easy application,biogas slurry has become a core component of circular agriculture,as an ideal alternative fertilizer.This research was carried out in Luo Dun village,Changshou,Jiangsu province in 2016-2017.The tested cultivars were Nanjing 5055 and Yangmai 16.This study set up different substitution ratios to study the effects of the yield,plant morphology,physi-chemical characters,soil nutrients and greenhouse gases of rice and wheat under the conditions of equal nitrogen.Based on the results of this study,a reasonable proportion of biogas slurry and chemical fertilizer was put forward,which provided a basis for innovating circular agriculture.The main results were summarized below.1)The growth of rice and wheat was influenced by the substitution of chemical fertilizer with biogas slurry.The number of tillers,dry matter accumulation and yield of wheat were significantly higher than that of total chemical fertilizer treatment when the application ratio are 75%and 50%.The yield of the 75%biogas slurry treatment during rice growing season is 57.73%higher than blank treatment,while the yield of the 50%biogas slurry treatment during wheat growing season is 73.44%higher than blank treatment.When biogas slurry was applied,the annual yield of rice and wheat treated by 75%biogas slurry was the highest.The difference between 75%biogas slurry treatment and total fertilizer treatment was not significant.With the increase of biogas slurry,the annual yield of rice and wheat tended to first increase then descend.When the substitution ratio of biogas slurry is 75%,the yield of rice was high and the nitrogen and phosphorus of soil surface water was low.2)With the increase of biogas slurry,the nitrogen content in allorgans of rice plants increas-ed first and then decreased while the nitrogen content increased in all organs of wheat plants.The phosphorus content in rice grain was highest when treated with 75%biogas solution while the phosphorus content in wheat grain was highest when treated with 100%biogas solution,and both of two phosphorus contents were significantly higher than the phosphorus content in grain of the whole fertilizer treatment.3)Different substitute proportion of biogas slurry has different effects on soil available nutrients.Total nitrogen content of soil increased first and decreased soon with the development process of rice and wheat.The soil total nitrogen(TN)of 25%biogas slurry treatment during rice growing season and 50%biogas slurry treatment during wheat growing season were the highest in this experiment.The soil available nitrogen(AN)of 75%biogas slurry treatment during rice growing season and 50%biogas slurry treatment during wheat growing season were the highest in this experiment,but there is no significant difference with the soil available nitrogen(AN)of 100%chemical fertilizer treatment.4)After using biogas slurry,the rule of greenhouse gases(CO2?CH4?N2O)emission between different treatments in basically the same,in this experiment.There is a trend to increase CO2?CH4?N2O emissions when chemical fertilizer was replaced by biogas slurry during wheat growing season while the emissions of CO2 trend to decrease during rice growing season.