Biochar has been proved to be an important soil amendment to alleviate soil phosphorus (P) in the paddy crops. However, the role of specially prepared biochar (N-enriched biochar) on the distribution and transformation of P soil in and rice leaves needs to be revealed. In this study, we studied in a field experiment the effects of two different levels of application of N-enriched biochar on the P fractions of soil and leaves. The results showed that: (1) in early rice, both rates of N-enriched biochar increased soil concentrations of labile inorganic P (Pi) (+51.5 % and +66.2 %, respectively) and labile organic P (Po) (+167 % and + 76.9 %, respectively) and moderately labile Pi (+37.8 % and +27.8 %, respectively) and decreased soil concentration of moderately labile Po (-17.0 % and -52.7 %, respectively) in the 0-15 cm layer. Soil total P concentration was positively correlated with soil labile P fractions and moderately labile Pi concentrations (p < 0.05); (2) in early and late rice, application of the biochar at 4 t ha-1 increased rice leaf concentration of inorganic (+13.3 % and +34.8 %, respectively), nucleic acid (+24.2 % and +13.0 %, respectively) (p < 0.05). The foliar inorganic and nucleic acid P concentrations were positively correlated with foliar total P concentrations; (3) redundancy analysis showed that with the application of N-enriched biochar, soil total carbon (C), nitrogen (N) and P concentration were important factors affecting the chemical forms of soil P, while soil organic matter, soil total P and leaf total P content were important factors affecting the chemical forms of leaf P; (4) allometric growth models showed that under the application of N-enriched biochar, 0-30 cm soil labile Po concentration was positively related to leaf concentration of nucleic acid P, 0-15 cm soil moderately labile Pi concentration was positively related to leaf concentration of inorganic P and nucleic acid P. Thus, this study provides evidence that N-enriched biochar increase the soil P-availability of labile and moderately labile P that in turn improved rice plants P use efficiency.
Keywords: Leaf phosphorus chemical form; N-enriched biochar; Paddy field; Physical and chemical properties of soil; Soil phosphorus fractions.
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