Soil microbial community structure affected by biochar and fertilizer sources

Use of organic fertilizer or organic amendments can potentially mitigate the deleterious environmental impacts of inorganic fertilizers in agroecosystems, but they can also affect soil microorganisms which have not been well defined. The aim of this research was to evaluate an incorporation of poultry-waste based organic fertilizer in various combinations of inorganic fertilizer and amendment with biochar on soil microbial properties after two growing seasons of serrano chili peppers. Treatments included combinations of inorganic N with different rates (0%, 50%, 75% and 100% of total N supply) of organic N (org-N) and inorganic N with amendment of three rates (10, 30 and 50 t ha(-1)) of a coconut shell biochar. After two years of application, the amounts of total, arbuscular mycorrhizal fungal (AMF), and Gram positive and Gram negative bacterial phospholipid fatty acid (PLFA) increased significantly at the higher rates of biochar compared to those at lower rates, unfertilized, and non-amended soil. However, significant differences were not observed for fungal PLFA between inorganic N with biochar and those without addition of biochar. Organic N application also increased (with the highest from 75% rate) the amounts of total, Gram positive and Gram negative bacterial and AMF PLFAs compared to unfertilized and inorganic N treatments, but the amounts of fungal PLFA significantly decreased as organic N application rate increased. All the rates of biochar and org-N amendments increased the pepper yield compared to unfertilized and inorganic N treatments in the second year. Results indicate that soil amendment with biochar or incorporation of organic fertilizer for about two years affected microbial community biomass, composition and crop yield. Thus, in conventional farming, the combined use of inorganic fertilizers with org-N source or organic amendment with biochar can improve soil health and crop productivity.