| In order to achieve high-quality development in agriculture and balance ecological and green development,it is necessary to ensure agricultural productivity while also considering the environmental impact.Currently,ecological and environmental issues such as global warming,increased atmospheric nitrogen deposition,declining soil quality,and agricultural non-point source pollution are deeply affecting human life.Greenhouse gas emissions from farmland and water and soil environmental issues are hot research topics.Organic material application can improve soil fertility and enhance cultivated land quality,while also achieving the resource utilization of agricultural waste.Straw and biogas slurry are the main organic wastes of planting and breeding,and achieving the return of straw and biogas to the field is of great significance to the combination of planting and breeding and sustainable agricultural development.This study focuses on the effects of the combined application of straw and biogas slurry on rice growth and the water-soil-air environment in paddy field systems through field experiments,aiming to provide theoretical basis and technical support for the replacement of chemical fertilizers with biogas slurry and to promote high-quality agricultural development.The experiment was conducted during the rice season from 2021 to 2022,with six treatments including blank control(CK),single biogas slurry application(BF),straw application(SF),combined application of biogas slurry and straw(BSF),single chemical fertilizer application(NF),and combined application of chemical fertilizer and straw(NSF).During the whole rice growth period,greenhouse gas emissions,ammonia volatilization,water and soil carbon and nitrogen indicators were measured,as well as rice yield,growth characteristics,nutrient absorption and distribution of rice organs,and straw decomposition characteristics.The main research results are as follows:1.In this experiment,methane emissions from rice fields were mainly concentrated during the tillering and jointing stages of rice growth,accounting for approximately 90%of the total emissions throughout the entire growth period.Methane emissions significantly decreased after rice entered the heading stage.Straw application significantly increased methane emissions,and the methane emission levels from each treatment,from high to low,were SF>NSF>BSF>BF>CK>NF,with emission ranges between 4.27-132.38 kg-hm-2.Nitrous oxide and ammonia volatilization in the rice field were highest in the BSF treatment,reaching 2.91 kg·hm-2.2.Within one week after fertilization,nitrogen concentrations in the rice field water environment were generally high,which is a critical period for reducing nitrogen runoff and leaching losses.Ammonium nitrogen(NH4+-N)accounted for the majority of the total nitrogen(TN)in the surface water of the rice field,with a content of over 85%of the total nitrogen content.Compared to the chemical fertilizer treatment,the application of biogas slurry effectively reduced the NH4+-N levels in the surface water after basal fertilizer application.Nitrate nitrogen(NO3N)dominated the total nitrogen in the leachate of the rice field,accounting for over 80%of the total nitrogen content.The BSF and NSF treatments reduced the NO3--N levels in the leachate.The NSF treatment showed multiple peaks of total phosphorus(TP)in the surface water,while the total potassium(TK)in the surface water showed a general trend of BSF>BF>other treatments.The BSF treatment maintained a leading level of total organic carbon(TOC)in the surface water throughout the entire growth period.3.The coupling of biogas slurry and straw effectively ensures rice yield.The rice yield in the BSF treatment was similar to that in the NF treatment,with yields of 8.78 and 8.68 t/hm2,respectively.The release of nitrogen and phosphorus from straw and biogas slurry was rapid from the day of application to the 10th day,with nitrogen release rates ranging from 2.95%to 5.05%per day and phosphorus release rates ranging from 2.80%to 5.35%per day.Subsequently,nutrient release rates slowed down.The combined application of biogas slurry and deep burial of straw further increased the release levels of nitrogen and phosphorus in this experiment. |
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