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.

Antioxidant properties of Du-zhong (Eucommia ulmoides Oliv.) extracts and their effects on color stability and lipid oxidation of raw pork patties.

The ethanol extracts from leaf, roasted cortex, and seed of Du-zhong ( Eucommia ulmoides Oliv.) were examined for total phenolics content (TPC) and total flavonoids content (TFC). The antioxidant activity of the extracts was evaluated by measuring the radical scavenging activity of 2,2-diphenyl-1-picrylhydrazyl (DPPH), ferric reducing antioxidant power (FRAP), and lipid peroxidation inhibition capacity in a beta-carotene/linoleic acid system. Du-zhong leaf extract was found to have the highest TPC content (94.46 +/- 1.17 mg of gallic acid equiv/g of solid extract) and TFC content (61.36 +/- 0.59 mg of catechin equiv/g of solid extract). In the above three antioxidant assay systems, Du-zhong leaf extract also exhibited the strongest antioxidant capacities, followed by roasted cortex extract and seed extract. The effects of Du-zhong extracts (leaf, roasted cortex, and seed) on lipid oxidation, meat color, and metmyoglobin (MetMb) formation in raw pork patties were investigated and compared with that of butylated hydroxytoluene (BHT) during refrigerated storage at 4 degrees C for 8 days. The results indicated that the addition of leaf extract at 0.1% (w/w), roasted cortex extract at 0.1% (w/w), and BHT at 0.01% (w/w) decreased day 8 TBARS values by 35, 20, and 37%, respectively. Du-zhong leaf extract at 0.1% (w/w) also exhibited a certain stabilizing effect on meat redness a* value and retarded the formation of MetMb. This study suggests that Du-zhong leaf extract may be a potential source of natural antioxidants.