Global Potential Effects Analysis of Biochar on Crop Yields and Soil Quality

Biochar has been widely used for soil improvement, but uncertain results persist due to diverse biochar characteristics, soil properties, and crop responses. Therefore, the effects of biochar on crop yields and soil quality were evaluated using effect sizes from 1011 paired data points from field trials, based on a global meta-analysis method. The results indicated that biochar with a higher total phosphorus concentration (≥1.0%), total carbon concentration (≥70%), specific surface area (≥50 m2 g-1), and biochar application rates of 10–30 t ha-1 are optimal for improving crop yields. Biochar made from manure (effect size, 42%) exceeded that made from ligneous (22%) or cereal (12%) material. Porous, acidic, or young soil types are optimal for biochar application, while sandy and clay soils are preferred over loam soil. Soils with lower available nitrogen (