Pre-activated biochar by fertilizers mitigates nutrient leaching and stimulates soil microbial activity

Background Previous studies have suggested that the targeted application of biochars in agricultural soils may benefit soil health and crop production. Physico-chemical properties of soils after biochar addition have been explored, but less is known about how microbial parameters respond. Therefore, impact of biochar (NB), mineral fertilizer-activated biochar (AB), or mineral fertilizer (MF) application on selected chemical and microbial parameters of lettuce-planted soil was evaluated in a pot experiment. Results In comparison to the control, soil enzymes activities, related to carbon (C), nitrogen (N), and phosphorus (P) cycling, and their content in plant biomass, were significantly increased by the addition of mineral fertilizer with or without biochar (MF, NB + MF). Conversely, microbial respiration (basal and substrate induced) was highly responsive to the activated biochar amendment (AB) as compared to other treatments. N, P, and potassium (K) concentrations in soil pore water were stabilized by the mineral fertilizer-activated biochar, indicating reduced leaching and the likelihood of increased longevity of these nutrients in soils. Enhanced carbon acquisition and mitigated nitrogen acquisition in soil of the most experimental treatments were coupled with higher crop (lettuce) biomass. Conclusions Our study demonstrates that the application of biochar both with and without mineral fertilizer has the potential to enhance microbial activity and fertility in the tested agricultural soil, but that leaching of fertilizer-borne nutrients may be mitigated by the activation process.