Biochar addition affected nutrient leaching and litter decomposition rates in boreal sandy soils

Effects of biochar addition on litter decomposition rates, nutrient leaching and soil moisture were tested in two boreal agricultural soils; a sandy till and a medium fine sand. Three litter bags were buried in soil basins, which were stored in the dark for 31 and 19 weeks in the sandy till experiment and medium fine sand experiment, respectively. Once per each temperature period, the soil was saturated in order to collect excess water for nutrient analyses. Biochar increased the decomposition rate of N-rich litter but did not affect the decomposition of N-poor litter. PO43--P and NO2--N were released from the biochar to the leached water and thus leaching of PO43--P, NO2--N and total P was increased in the soil with the finer texture. However, biochar retained water after heavy irrigation and leaching of PO43--P and total P was not increased on the coarser soil. Although pure biochar adsorbed NH4+-N from nutrient solutions, NH4+-N leaching from both soil types was generally not affected by biochar. Leaching of nitrate NO3--N and total N was decreased on both soils due to retention by the biochar.