Phosphorus fractions in biochar-amended soil — chemical sequential fractionation, <sup>31</sup>P NMR, and phosphatase activity
Dianyun Cao, Yu Lan, Xu Yang, Wenfu Chen, Linlin Jiang, Zhengchao Wu, Na Li, Xiaori Han
Abstract
In this study, we assessed the effects of biochar application for five years on soil phosphorus (P) factions by chemical sequential P fractionation, phosphatase activity, and 31P NMR. Four treatments were included in this research: two biochar (0 and 2.63 t ha−1) levels blended with two P fertilizer levels (0 and 26 kg P ha−1), respectively. We found elevated levels of soil pH, total carbon (C), and total P in soil exposed to biochar. The inorganic (Ca8 – P, Al – P, Fe – P, and Ca10 – P) and organic (LOP and HROP) P fractions were all enhanced by biochar regardless of the application of P fertiliser. 31P NMR spectra further showed that ortho – P, monoester – P, and diester – P levels in the soil with added biochar combined with P fertiliser were 464.5 mg kg−1, 74.3 mg kg−1, and 13.9 mg kg−1, respectively, which were the highest among all treatments. Biochar application increased alkaline phosphomonoesterase activity by 24.4–32.7% and decreased phosphodiesterase activity by 10.2–11.0%. In conclusion, biochar application significantly improves soil P fractions and regulates phosphatase activity.