[Impacts of biochar and phosphorus application on soil phosphorus availability and soybean phosphorus uptake]. / ä¸åŒç£·æ°´å¹³é æ–½ç”Ÿç‰©ç‚­å¯¹åœŸå£¤ç£·æœ‰æ•ˆæ€§.

Biochar is beneficial to soil phosphorus (P) availability and crop growth, but the effects vary greatly across different soil types. We investigated the effects of rice straw biochar (4% of total mass) and P application (0, 30, and 90 kg P·hm-2) on soil P availability, phosphomonoesterase activity, and soybean P uptake by using lateritic red soil (pH 4.91) and cinnamon soil (pH 7.24) as test materials. The results showed that biochar application at different P levels significantly increased available P and total P in both soils. Biochar application with 30 kg P·hm-2 increased soil available P with maxima at 192.6% and 237.1% in lateritic red soil and cinnamon soil, respectively. Biochar application with 30 kg P·hm-2 in lateritic red soil significantly increased the activity of alkaline phosphomonoesterase by 78.9%, decreased the content of active organic P by 39.3%, and subsequently stimulated soybean P absorption and growth. Biochar amendment significantly reduced active organic P content in cinnamon soil, but did not affect soil phosphomonoesterase activity and plant growth. The content of active organic P was significantly negatively correlated with soil available P content. In summary, the effect of biochar on soil P availability varied across different soil types (lateritic red soil > cinnamon soil) and P levels (better at 30 kg P·hm-2). Our results could provide scientific basis for a promising application of biochar in reducing the amount of P fertilizer and increasing soybean P uptake, especially in lateritic red soil.

Biochar application under low phosphorus input promotes soil organic phosphorus mineralization by shifting bacterial phoD gene community composition.

Biochar has the potential to enhance microbial-mediated phosphorus (P) cycling in soils, but the underlying mechanisms remain largely unknown. We hypothesized that biochar amendment could enhance the production of acid and alkaline phosphomonoesterase, phosphodiesterase and P mineralization, which may vary depending on the P input. To test this hypothesis, we assessed the impacts of rice straw biochar application (0 and 4%) under different P-input rates (0, 30 and 90 kg P ha-1) on the relationships among P fractions, phosphatase activities and alkaline phosphomonoesterase-encoding bacterial (phoD gene) communities in an acidic soil. Biochar application under low P input (< 30 kg P ha-1) significantly increased the activities of phosphodiesterase and alkaline phosphomonoesterase but not that of acid phosphomonoesterase and depleted organic P. The results from the structural equation model revealed a dominant role of alkaline phosphomonoesterase in P mineralization. The increase in alkaline phosphomonoesterase activity was not related to an increase in phoD gene abundance but was due to a shift in community composition, which was primarily driven by the soil C:P ratio. Microbial network analysis demonstrated a more complex phoD gene community with more functionally interrelated groups as a result of biochar application under low P input than under high P input. Moreover, the specific enrichment of Micromonosporaceae under C-rich and P-poor conditions may play a critical role in alkaline phosphomonoesterase production and potential P mineralization. In conclusion, we demonstrated that biochar application under low P input supports a more organized phoD gene community and preferentially enriches taxa in terms of their capacity for P mineralization, which in turn may enhance P bioavailability and plant P acquisition.