Biochar Functions as Phosphorous Fertilizers in an Alkaline Alluvial Soil

With the depletion of global phosphorous (P) reserves, finding alternatives to P fertilizers has been gaining more and more attention. This study was conducted to identify whether biochar application could improve P availability in a P-deficient alkaline alluvial soil. Unground biochar contained a high level of 692 mg kg−1 extractable P, over 100 times more than that in the soil. Extractable P content increased significantly with the decrease of biochar particle size. There was a significant positive correlation between soil available P content and biochar application rates. The pot experiment showed that biochar application significantly increased the soil available P content before sowing, and significantly improved the aboveground biomass of soybean and promoted P uptake at harvest. Biochar, as containing abundant extractable P, could go partly on substituting mineral P fertilizers as well as promote plant growth and reduce P fertilizer application in agriculture.