Effect of Biochar on the Nitrogen Mineralization of Commercial Organic Fertilizers in Both Mineral Soil and Organic Potting Media

As interest in biochar as a soil amendment increases, the co-application of biochar and fertilizer warrants investigation. Biochar may improve soil properties, affect crop yields, and mitigate environmental impacts, but more work is needed to determine its effect on nitrogen (N) cycling from commercially available organic fertilizers. A 102 d laboratory incubation was conducted to better understand the effect of three rates of biochar (0%, 5%, and 10%) on net N mineralized from (1) mineral soil (Cecil sandy loam), (2) organic peat-based potting media, and (3) two commercial organic fertilizers (feather meal and meal-based pellet mix) applied to the mineral soil or the potting media. After 102 d, the biochar treatments did not affect net N mineralized from the mineral soil but decreased (from 190 to −286.9 mg N kg−1) the net N mineralized from the potting media, likely due to N immobilization. Biochar applied at 5 or 10% did not affect the amount of organic N mineralized from the organic fertilizers applied to potting media (average 58.9%), but biochar at 5% decreased from 46.5 to 28.1% of organic N mineralized from the organic fertilizers applied to mineral soil.