Abstract
Biochar and chemical fertilizer have been widely used in agriculture. Most studies have proved that they not only alter soil nutrient content, but also have an impact on soil microbial communities. However, the effects of biochar and chemical fertilizer application on the overall bacterial community in different soil types under rainfall conditions are not yet understood. We took rainfall as a fixed influencing factor and selected four typical soils of China to investigate the bacterial effects of biochar and chemical fertilizer at 25 mm rainfall, and to identify specific differential bacteria and their functions, and to explore the changes of the bacterial community structure of different soil types. The depth of simulated rainfall was 25 mm each time. Yellow-brown soil, fluvo-aquic soil, lou soil, and black soil were chosen for experiment and each soil was divided into four treatments, included non-biochar and non-fertilizer (CK), fertilizer alone (F), biochar alone (C), and combination of biochar and fertilizer (FC). The results indicated that biochar and fertilizer have a more significant effect on bacterial communities in acidic soils. The amendment of biochar and fertilizer alone or together identified 3 (f_Oxalobacteraceae, f_Solibacteraceae_Subgroup_3, f_Sphingomonadaceae), 5 (f_Chitinophagaceae, f_Comamonadaceae, f_Geobacteraceae, f_norank_o_SC-I-84, f_norank_c_OPB35_soil_group), 1 (f_Blastocatellaceae_Subgroup_4) and 0 differential bacteria in yellow-brown soil, fluvo-aquic soil, lou soil, and black soil by statistical test. In yellow-brown soil, the application of biochar alone increased the relative abundance of potential pathogens within the Sphingomonadaceae and reduced the relative abundance of beneficial bacteria in Solibacteraceae, but the addition of biochar and fertilizer together increased the relative abundance of some beneficial bacteria in Oxalobacteraceae. In fluvo-aquic soil, both biochar, and chemical fertilizers promoted the relative abundance of some beneficial bacteria belonging to Chitinophagaceae, Comamonadaceae, and Geobacteraceae that may be involved in nutrient cycling, degradation of plant residues and increase of metal tolerance. The interactions between acidic soil bacterial communities and measured soil parameters including pH, organic matter were found to be statistically significant. Results from this study revealed that it is necessary to formulate biochar and fertilizer application schemes based on different soil types.
Highlights
Chemical fertilizers have been applied in agriculture for a long time in improving soil nutrient contents and ensuring crop growth requirements
After the addition of biochar, chemical fertilizers, and simulated rainfall, the basic physicochemical properties of different soils were changed to different degrees (Table 1)
From the results of yellow-brown soil (Figure 2A), the amendment of biochar alone increased the relative abundance of potential pathogens within the Sphingomonadaceae and reduce the relative abundance of beneficial bacteria in Solibacteraceae, but the application of biochar and fertilizer together improved the relative abundance of some beneficial bacteria in Oxalobacteraceae possibly by promoting nutrient cycling
Summary
Chemical fertilizers have been applied in agriculture for a long time in improving soil nutrient contents and ensuring crop growth requirements. Most studies suggested that biochar could affect the abundance of microorganisms due to its special structure and nutrient holding capacity or indirectly change the physicochemical properties of the soil (Lehmann et al, 2011; Ameloot et al, 2013; Jaafar et al, 2014). Some previous studies reported that the microbial communities in the soil change differently with long-term and short-term biochar application, and the bacterial diversity in the soil changes significantly in a short-term biochar amendment (Jin, 2010; Khodadad et al, 2011). Through the analysis of previous studies, it was proposed that the effects of biochar on soil microbes are not uniform due to the diversity of biochar and soil types. Some studies suggested that fertilizers could change soil microbial composition, while others did not find significant effect (Kirchmann et al, 2013; Geisseler and Scow, 2014; Geisseler et al, 2016)
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