Zhao Shi-Xiang, Yu Xiao-Ling, Li Zhong-Hui, Yang Yan, Zhang Xia, Wang Xu-Dong, Zhang A-Feng
College of Natural Resources and Environment, Northwest A & F University, Yangling 712100, China.
Key Laboratory Plant Nutrition and the Agri-environment in Northwest China, Ministry of Agriculture, Yangling 712100, China.
Huan Jing Ke Xue. 2017 Feb 8;38(2):769-782. doi: 10.13227/j.hjkx.201604059.
Application of biochar (BC) is an important way to increase soil organic carbon sequestration. At the same time, the effect of BC on fractions and properties of soil humic substances is concerned. A laboratory experiment was conducted to study the influences of BC pyrolyzed at different temperatures on the composition and properties of humic substances. The modified method for the extraction and fractionation of humic substances was adopted in this work. The carbon (C) contents of Humin (Hu), Humic acids (HA), Fulvic acids (FA) were analyzed by the thermal oxidation of KCrO and TOC analyzer, and the optical properties of HA and FA were measured by using spectrophotometer. The results showed that the increasing temperature (from 300 to 600℃) decreased like-humic substances (LHS) from 10.93 g·kg to 0.26 g·kg, while the structure of theLHS tended to be complicated. Compared with control treatment (CK), the addition of BC produced under 400℃ increased the contents of HA and FA (after 240 d incubation a lower FA content was found in treatments) and increased as BC application rate increased, after 360 d of incubation, BC300 and BC400 significantly increased by 69.93% and 48.75% for HA (<0.05), while decreased by 1.35% and 5.19% for FA. Higher contents of HA and FA were found in soil samples amended with BC prepared at above 400℃ only during the initial period of 3-10 d of incubation and increased as BC application rate increased, at the end of the incubation, the contents of HA and FA significantly decreased by 34.38%, 44.48% in BC500 treatments and 42.84%, 49.27% in the BC600 treatments (<0.05). During the incubation, the addition of BC significantly increased the contents of Hu (<0.05), and the treatments amended with BC500 were the highest. The addition of BC decreased the relative contents of HA and FA, while increased the relative content of Hu, indicating that the proportion of relatively stable organic carbon in the soil was increased. The ratio of HA/FA (H/F) varied between 0.88 and 2.52 and increased with decreasing pyrolysis temperature and increasing BC application. A significantly lower color tonal coefficient (Δlg) and /6 values in treatments amended with BC produced at temperatures above 400℃, indicating that higher temperatures derived BC complicated the structure of soil humic substance, while an opposite rend was observed in treatments amended with BC produced at temperatures under 400℃. Considering the improvement of the stability of organic carbon, when the BC products were applied to the Loutu soil, 500℃ was the optimal temperature for preparing apple-derived BC not only because it could significantly increase the content of inert soil organic carbon, but also improve the quality of the soil as a result of enhancing the degree of soil humification.
施用生物炭（BC）是增加土壤有机碳固存的重要途径。同时，生物炭对土壤腐殖物质组分和性质的影响也备受关注。开展了一项室内试验，研究不同温度热解制备的生物炭对腐殖物质组成和性质的影响。本研究采用改进的腐殖物质提取和分级方法。采用重铬酸钾氧化和总有机碳分析仪分析胡敏素（Hu）、胡敏酸（HA）和富里酸（FA）的碳（C）含量，用分光光度计测定HA和FA的光学性质。结果表明，随着热解温度升高（从300℃到600℃），类腐殖物质（LHS）含量从10.93 g·kg降至0.26 g·kg，但其结构趋于复杂。与对照处理（CK）相比，400℃以下制备的生物炭添加后增加了HA和FA的含量（培养240 d后各处理中FA含量有所降低），且随生物炭施用量增加而增加，培养360 d后，BC300和BC400处理的HA含量显著增加69.93%和48.75%（P<0.05），FA含量分别降低1.35%和5.19%。400℃以上制备的生物炭添加到土壤样品中，仅在培养初期3-10 d内HA和FA含量较高，且随生物炭施用量增加而增加，培养结束时，BC500处理的HA和FA含量显著降低34.38%、44.48%，BC600处理分别降低了42.84%、49.27%（P<0.05）。培养期间，生物炭添加显著增加了Hu的含量（P<0.05），其中BC500处理的含量最高。生物炭添加降低了HA和FA的相对含量，增加了Hu的相对含量，表明土壤中相对稳定有机碳的比例增加。HA/FA比值（H/F）在0.88至2.52之间变化，随热解温度降低和生物炭施用量增加而升高。400℃以上制备的生物炭添加处理的色调系数（Δlg）和E4/E6值显著较低，表明高温制备的生物炭使土壤腐殖物质结构复杂化，而400℃以下制备的生物炭添加处理则呈现相反趋势。考虑到有机碳稳定性的提高，当将生物炭产品施用于塿土时，500℃是制备苹果源生物炭的最佳温度，这不仅是因为它能显著增加惰性土壤有机碳含量，还能通过提高土壤腐殖化程度改善土壤质量。
