Biochar application regulates organic phosphorus fractions and the release of available phosphorus in farmland soil

The relationship between phosphorus (P) related enzymatic activity and organic P turnover remains unclear, particularly in the context of biochar application. Field experiments were conducted on Phaeozem and Luvisol soil types to investigate the effects of biochar application rates - 0 t ha^-1 (CK), 22.5 t ha^-1 (D₁), 67.5 t ha^-1 (D₂), and 112.5 t ha^-1 (D₃) - on soil organic fractions using ³¹P nuclear magnetic resonance (NMR) spectroscopy and relevant phosphatase activity.

The application of biochar increased the soil organic carbon (SOC), pyrophosphate (pyro), and orthophosphate (ortho) content, as well as the acid phosphomonoesterase (AcP), alkaline phosphomonoesterase (AlP), inorganic pyrophosphatase (IPP), and phosphodiesterase (PD) activities. Biochar application also increased soil organic P (OP_a), the sum of inorganic P forms (IP), ortho, monoesters, and myo-IHP contents, the pH value, AlP and PD activities in Phaeozem, but it significantly reduced diesters, polyphosphate (poly) contents, and IPP and AcP activities compared to those in Luvisol. Acid phosphomonoesterase and PD activities also showed an opposite trend in Luvisol. The structural equation model showed that the potential mechanism of organic P turnover in response to biochar application differed depending on the soil types, potentially influenced by P availability.

Overall, the findings of this study enhance the comprehension of the variation of P fractions and their availability in the context of biochar application for agricultural production in northeastern China. © 2024 Society of Chemical Industry.