Effect of Biochar on pH of Alkaline Soils in the Loess Plateau: Results from Incubation Experiments

An incubation experiment was conducted to determine the effects of biochar on the pH of alkaline soils. Five types of alkaline soils collected at the Loess Plateau and one type of biochar with a slightly lower pH than the soils were used. After incubation for 4 months and 11 months, the control soil and biochar-amended soils (4, 8 and 16 g of biochar/kg of soil) were sampled and tested. The application of alkaline biochar did not increase the soil pH but instead produced a decreasing pH trend, especially with higher biochar application rates. The decrease in soil pH was more significant at the 10 cm to 20 cm layer than in the 0 cm to 10 cm layer. The F soil type (Aeolian sandy soil), which had the highest pH, showed the largest decrease in pH after 11 months of incubation. Acidic materials produced by the oxidation of biochar and organic matters may have caused the pH decrease. The high soil cation exchange capacity caused by the biochar application might restrict the soil salinization process to some extent. copyright 2012 Friends Science Publishers