Co-applying biochar and paper mill biosolids (PB) improves the potential of these by-products as soil amendments. Assessing the response of soil microbial communities to the co-application of biochar and PB is of great importance to further understanding their effectiveness. This hypothesis was tested in a 112-day incubation study performed separately on two acidic soils (Kamouraska clay and St-Antoine sandy loam) using two PB types (PB1 with C/N = 24 and PB2 with C/N = 13), co-applied with one of three rates (0%, 2.5%, and 5% w/w) of pine (Pinus strobus L.) biochar. An unamended control and a mineral-fertilized treatment were used as a reference. In the Kamouraska clay soil, co-applying 5% biochar and any PB increased microbial activity compared to PB-only application, as indicated by the fluorescein diacetate (FDA) hydrolysis assay. In both soils, co-applying biochar and PB did not affect microbial diversity and community structure compared with PB only. The application of any PB, however, increased microbial activity in both soils, while only PB2 shifted microbial community structure. Within each amendment and in both soils, microbial activity was lower at day 112 than at days 28 and 56, while major temporal shifts were observed only for bacterial community structure. Indeed, the difference in bacterial community structure between amendments was more pronounced at day 112. This study suggests that co-applying biochar and PB can improve soil properties than application of PB alone by increasing soil microbial activity without side effects on microbial diversity and community structure, especially in acidic clay soils.

并用生物炭和造纸厂生物固体（PB）可提高这些副产物作为土壤改良剂的潜力。评估土壤微生物群落对生物炭和PB共同施用的反应，对于进一步了解其有效性非常重要。该假设在112天的孵育研究中得到了检验，该研究分别在两种酸性土壤（Kamouraska粘土和St-Antoine沙壤土）上使用两种PB类型（C / N  = 24的PB1和C / N  = 13的PB2 ）进行， -施用三种比率（0％，2.5％和5％w / w）的松树（Pinus strobusL.）生物炭。未修改的对照和矿物质施肥的处理用作参考。在Kamouraska粘土中，与仅使用PB相比，与PB单独施用相比，共同施用5％的生物炭和任何PB都增加了微生物活性，这通过荧光素双乙酸酯（FDA）水解测定法表明。在两种土壤中，与仅使用PB相比，同时施用生物炭和PB不会影响微生物多样性和群落结构。但是，任何一种PB的施用都增加了两种土壤中的微生物活性，而只有PB2改变了微生物群落结构。在每种改良剂中和两种土壤中，第112天的微生物活性均低于第28天和第56天，而主要的时间变化仅在细菌群落结构上观察到。实际上，在第112天，修正之间细菌群落结构的差异更加明显。