| Organic fraction of municipal solid waste(OFMSW)-based biochar is abundant in nitrogen and organic matter. Used as a soil amendment, this biochar may alter N transformation in scantily-N purple soil by changing the soil properties and microbial community structure. In the effort to investigate the effects of OFMSW-based biochar on bacterial community structure, soil characteristics, especially nitrogen condition, a 12-month pot incubation experiment was conducted. A purple soil in Chongqing, China, was amended by biochar which derived from OFMSW and was pyrolyzed at 700°C. Four treatments were built based on various biochar application rates which are 0%, 1%, 3% and 5% w/w and were named as 0%BC, 1%BC, 3%BC and 5%BC. Several physicochemical properties of soil samples were monitored. Simultaneously, the DNA extracted form soil samples were sequenced on Mi Seq platform to identify the bacterial community structure.The p H of biochar amended soil slightly declined at early 5 months but got a value that similar with control(around 8.0) in the rest of the incubation. 3%BC and 5%BC got significantly higher soil organic matter(SOM) and total nitrogen(TN) concentration than control and the improvement climbed following the increased biochar application rate. Soil NH+ 4-N adsorption capability decreased in biochar amended treatments while soil ammonia and 3NO-N-concentration were elevated in biochar treatments and the 3%BC worked best. However, the absolute concentration of ammonia and 3NO-Nreminded low and nitrogen fertilizers are still necessary.The no-biochar soil and biochar amended soil showed discernibly different bacterial community structure during the incubation. ?-diversity of the bacteria diminished in 3% and 5% biochar treatment pots. The relative abundance of the several phyla that associated with nitrification and denitrification, including Proteobacteria, Firmicutes, Actinobacteria, become more abundant in biochar amended soil. The classes in each phylum reacted differently to environmental variables. Nitrospira class was less abundant in 5%BC than other treatments.At genera level, the major genera made varied responses to soil environmental variables. The canonical correspondence analysis(CCA) showed that the main genera which can be well explained by environmental variables fell into 3 groups. The genera in Group 1 were more abundant in 3%BC and 5%BC treatments during the latter 6 months of the experiment. These genera were sensitive to environmental variations and were observed to be positively correlated to soil TN, SOM, soil 3NO-N-concentration and biochar application rate. The genera located in Group 2 had higher relative abundance in 1%BC and 3%BC treatments, they were less sensitive to soil TN, SOM and 3NO-N-concentration variation while positively correlated to soil +4NH-N adsorption capacity and ambient temperature. The relative abundances of genera in Group 3 were higher in 1%BC and these genera were negatively correlated with soil TN, SOM, 3NO-N-concentration, biochar application rate and ambient temperature but positively correlated with soil p H.In addition, the CCA also evidenced that, besides to the soil properties and climate condition that involved in current study, other environmental factors should be account for the shifts of the bacterial community structure since the two ordination axes of the CCA triplot combine to explained just 35.8% of the variations at genera level. According to the contribution of each environmental factors to bacterial community structure's variation, the monitored soil environmental variables would be ordered as TN(16%) > biochar application rate(15.8%) > SOM(15.7%) > NH+ 4-N adsorption capacity(13.3%) > p H(11.5%) >3NO-N-(10.3%). |
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