Effects Of Organic Fertilizer Substitution On Greenhouse Gas Emission From Farmland In Different Crop Rotation Systems

With the rapid development of livestock and poultry breeding industry in China,the reclamation of livestock and poultry breeding waste has received high attention from the state and the government.How to realize the scientific and reasonable utilization of organic fertilizer（solid organic fertilizer and biogas slurry）and how to reduce the greenhouse gas emission in the process of returning to farmland are the current research hotspots and emphases.Based on farmland in greenhouse gas emissions characteristics of unknown problems,southwest selected typical rice-bean crop rotation system and typical wheat-maize rotation system in North China Plain,based on dairy waste are studied for the matrix of organic fertilizer,anaerobic fermentation biogas slurry instead of chemical fertilizer farmland greenhouse gas emissions characteristics and agronomy effect（yield and nitrogen use efficiency）,analyzes the different fertilization on greenhouse gas emissions the key influence factor,discusses the reasonable utilization of livestock and poultry breeding waste（returning）mode.The main research results are as follows:1)In the rice-broad bean rotation system,compared with Y1（conventional fertilization）,the yield of rice crops in treatments Y3 and Y4（organic fertilizer）was significantly reduced,but the yield of broad bean crops was not significantly reduced,and the greenhouse gas emission intensity of farmland was increased by 23.61%and 25.00%,respectively.Y2（With 20%reduction of fertilizer）,the crop yield was not significantly reduced,but the greenhouse gas emission intensity was significantly reduced.The yield of rice(9.9 t·hm^-2)and broad bean(5.1 t·hm^-2)were significantly increased in the Y5（slow controlled fertilization treatment）,and the nitrogen uptake of crops was the highest,which were 150kg·hm^-2（rice）and 157 kg·hm^-2（broad bean）,and the greenhouse gas emission of farmland was significantly decreased.Fertilization increased the comprehensive warming potential of rice and broad bean during the whole growth period,which was 1.19¹.55 times higher than that without fertilization.From the perspective of short-term effect,the agronomic and environmental benefits of Y5(slow controlled fertilization,the nitrogen application amount in rice season is 156 kg·hm^-2,and the nitrogen application amount in broad bean season is 84 kg·hm^-2)reached the optimal level（crop yield significantly increased,and greenhouse gas emissions significantly decreased）.Although organic fertilizer treatment led to the decrease of rice crop yield and the increase of greenhouse gas emission,it had no significant effect on the yield of broad bean season.Y2（Fertilizer reduction treatment）showed no significant decrease in crop yield,but significantly reduced greenhouse gas emissions.2)Under biogas slurry irrigation,the seasonal characteristics of soil greenhouse gas emissions in wheat-maize rotation cycle do not change significantly,but it will increase the emission flux in a short period.In the global warming potential,there was no significant difference between T3（biogas slurry irrigation with ratio of water/biogas slurry:2:1,three times for wheat and one time for maize）and T4（biogas slurry irrigation with ratio of water/biogas slurry:2:1,four times for wheat and one time for maize）treatment and conventional fertilization（CF）treatment,and T1（biogas slurry irrigation with ratio of water/biogas slurry:2:1,one time for wheat and one time for maize）and T2（biogas slurry irrigation with ratio of water/biogas slurry:2:1,two times for wheat and one time for maize）were significantly reduced compared with conventional fertilization（CF）treatment.The greenhouse gas emission intensity（T3,T4）was not significantly different from conventional fertilization for two consecutive years,and T1 and T2 treatments were significantly lower than conventional fertilization（CF）.Considering the factors of GWP and crop yield,T2 treatment(biogas slurry irrigation 2 times in wheat season,biogas slurry irrigation 1 time in maize season,and nitrogen application rate is315kg·hm^-2)is the best fertilization mode.