Effects of Biochar Application Pyrolyzed at Different Temperatures on Soil Properties, Growth and Leaf Secondary Metabolite Accumulation in Cyclocarya paliurus

Abstract

Cyclocarya paliurus is a well-known multifunctional tree species and its leaves are in especially high demand for tea production and medical utilization in China. To meet the enormous requirements of its leaf production, lots of C. paliurus plantations have been established for harvesting the leaves, producing a large quantity of pruning residues during their management. In this study, biochar at different pyrolysis temperatures (300 °C, 500 °C and 700 °C) were prepared, utilizing the pruning residues, and the effects of biochar additions pyrolyzed at different temperatures on soil properties, growth and leaf secondary metabolite accumulation in C. paliurus were investigated. The results showed that the chemical properties and FT-IR spectra of wheel wingnut-based biochar were significantly influenced by the pyrolysis temperatures, and the application of biochars pyrolyzed at different temperatures significantly affected soil pH and nutrient availability, as well as the growth, nutrient uptake and secondary metabolite accumulation of C. paliurus seedlings (p < 0.05). Correlation analysis indicated that the total contents of polyphenols, flavonoids and triterpenoids in C. paliurus leaves were negatively correlated with the contents of total phosphorus (P) and total potassium (K) in the leaves, but positively correlated with the ratios of carbon (C)/nitrogen (N) and C/P. After 200 days of biochar treatment, the highest biomass production and leaf secondary metabolite accumulation in C. paliurus were obtained in the addition of biochar pyrolyzed at 500 °C. The findings from this pot experiment provide a potential application in C. paliurus plantations, though long-term field experiments are required to optimize the quantity of biochar addition, based on soil conditions and stand age at the planting sites.