Effects Of Biochar And Organic Fertilizer On Saline-alkali Soil N₂O Emissions In The North China Plain

As agricultural waste utilization patterns,biochar and organic fertilizer can be used as soil amendment to affect the nitrogen(N)cycle and nitrous oxide(N₂O).N₂O is considered one of the major greenhouse gases and agricultural soils are the main source of N₂O emissions due to nitrification and denitrification process.The experiments were conducted in Binzhou,Shandong province and the effects of biochar and organic fertilizer were evaluated on saline-alkalin soil for N₂O emissions under winter wheat-summer maize rotation system.According to the principle of equal nitrogen,the experiment included six treatments were used with three replications:CK(N:0.2 t·(hm²·a)^-1,P₂O₅:0.12 t·(hm²·a)^-1),C1(5 t·(hm²·a)^-1biochar),C2(10 t·(hm²·a)^-1biochar),C3(20 t·(hm²·a)^-1biochar),M1(7.5t·(hm²·a)^-1 organic fertilizer),M2(10 t·(hm²·a)^-1 organic fertilizer).The effects of biochar and organic manure on soil WFPS,p H,mineral nitrogen were investigated,nitrifying and denitrifying microorganism were studied by high-throughput sequencing during the wheat-maize rotation cycle.Aditionally,the influence mechanism of biochar and organic fertilizer on soil N₂O emissions were discussed in order to improve the soil nitrogen by increase the efficiency of nitrogen,and provide theory basis to reduce greenhouse gas emissions.The main results were as follows:(1)Normally biochar inhibited the N₂O emissions,while organic fertilizer stimulated the N₂O emission.The cumulative N₂O emissions were significantly higher in wheat season and accounted for 75.2%to 90.0%of the total annual emissions.Maize season was a key period to control N₂O emissions.Fertilization can stimulate a large amount of N₂O emission in saline-alkali soil.The results showed that organic fertilizer significantly increased the N₂O emission compared to the biochar.(2)Application of biochar and organic fertilizer could increased the content of MBC and MBN in the saline-alkali soil.The effect of organic fertilizer on soil MBC and MBN was greater than biochar.The soil p H and soil mineral nitrogen content were the key factors affecting of soil MBC and MBN.(3)Ammonia oxidizing bacteria(AOB)were the main contributors to nitrification in all treatments,and the nitrification was the main source of soil N₂O emission,and biochar and organic fertilizer impacted N₂O emissions by denitrification process.The genus Nitrosospira(40.7%-65.4%)of AOB had an absolute advantage in the each treatment and was the major player in nitrification.For the total abundance of denitrifiers significantly affected by biochar and organic fertilizer.Biochar decreased the abundance of nirK-type denitrifier in the maize season,but increased the abundance in wheat season.Application of biochar increased the abundance of nosZ-type denitrifier,and had no effect on the abundance of nirS-type denitrifier in the both season.Organic fertilizer had no significant effect on the abundance of denitrifiers in the maize season,while organic fertilizer significantly increased the abundance of nirK-and nosZ-type denitrifier in the wheat season,but had no significant effect on the abundance of nirS-type denitrifier.Denitrifiers were mainly affected by soil temperature,water-filled pore space(WFPS),p H,ammonium nitrogen(NH₄⁺-N)and nitrate nitrogen(NO₃^--N).