Biochar‐application rate and method affect nutrient availability and retention in a coarse‐textured, temperate agricultural Cambisol in a microcosm experiment

Abstract

Background Agricultural soils often require organic amendments, which improve crop yield and ecosystem services. Biochar has been proven to increase nutrient availability and retention in fine‐textured, tropical soils. Aims Here we determine how coarse‐textured, temperate soils react to different biochar‐application rates in different tillage systems. Methods We conducted a 6‐month laboratory incubation experiment in microcosms filled with a coarse‐textured, temperate agricultural soil to determine the effects of biochar‐application rate (none, low, or high, i.e., 0, 20, or 40 t dw ha−1, respectively) and application method (mixed into the soil or applied to the soil surface) on microbial activity and biomass, and nutrient availability and leaching. Results Microbial activity and biomass and contents of carbon, nitrogen, and phosphorus in leachates were higher in biochar‐addition treatments (by 134%, 37%, 372%, 28%, and 801%, respectively) than in the no‐addition treatment. The effect was stronger with the low than with the high biochar‐application rate. Biochar applied by both methods acted as a slow‐release fertilizer, but this effect was stronger when biochar was mixed into the soil. Although available nutrient contents in the soil remained high, nutrient leaching decreased with incubation time. This effect was especially evident when biochar was mixed into the soil. Conclusions Biochar is an effective organic amendment in coarse‐textured soils providing available nutrients. On the other hand, nutrient‐retention mechanisms develop slowly after biochar application and may be greater when biochar is mixed into the soil than applied on the soil surface.