Nitrogen Losses Throughiron Reduction Coupled With Anaerobic Ammonium Oxidation From Paddy Soils

The bacteria-mediated anaerobic ammonium oxidation under iron reducing conditions,termed Feammox,represents a process for alleviating N accumulation in anoxic soils.Fertilization,as an important agricultural strategy,needs to be investigated in order to determine its effects on nitrogen(N)removal via the Feammox process in paddy soils.In this study,a slurry incubation experiment was conducted in four fertilized paddy soils from Southern China using 15N-isotope tracing and qPCR techniques.Feammox reaction rates and related microbial communities were measured after soil incubation,and biochars were also used to detect the inner mechanism of Feammox mediated by electron shuttle.The abstract of this study was mentioned as follows:Firstly,the sequencing results of soil samples collecting from field with different fertilizer treatments showed that long-term fertilizer treatment increased the abundance of Feammox bacteria and iron-reduction bacteria,which indicates that a high potential Feammox rates might existed in fertilized soils.Secondly,through soil incubations,we measured the feammox rates,detected the microbial communities,and quantified the ecological contribution of Feammox to nitrogen losses in four different fertilized soils.The total nitrogen losses via Feammox in our study reached 3.64 kg N ha-1 year1 in non-fertilized soil and 15.97-24.91 kg N ha-1 year1 in fertilized soils,and the differences in Feammox A6 and electron shuttle caused by organic matters input were the major contributor to the variance.Finally,we used biochars as the source of electron shuttle to verify the influence of electron transfer on Feammox with different iron sources addition Our results demonstrated that the conductive "microbe-electron shuttle-iron mineral" networks,which bridge the gap between bacteria and iron sources,were the inner driven mechanism of Feammox process.