添加生物质炭对壤土热性质影响机理研究
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国家自然科学基金项目(41401241,41471180)、江苏省自然科学基金青年项目(BK20140724)


Effects of Biochar Addition on Thermal Properties of Loamy Soil
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the National Natural Science Foundation of China (Nos.41401241, 41471180),Natural Science Foundation of Jiangsu Province of China (No.BK20140724)

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    摘要:

    生物质炭添加对一系列土壤理化性质具有显著影响,然而其对土壤热性质的影响机理仍不明确。本研究结合田间定位试验和室内控制实验揭示了生物质炭添加对壤质土热性质的影响机理。两年田间区组试验中小麦秸秆生物质炭施用量设0 t hm-2、 25 t hm-2 和50 t hm-2三个水平。使用热脉冲法分别在室内控制土壤含水量和田间自然条件下测定土壤热容量、导热率和热扩散系数。同时测定了不同生物质炭处理下土壤容重、土壤水分特征曲线、孔隙分布以及作物生长季表层土壤含水量。结果表明,生物质炭添加会对土壤热性质产生显著影响,其主要途径为(1)通过降低土壤容重,增加土壤大孔隙,从而显著降低土壤导热率,对土壤热容量和热扩散系数也有降低效应,但受土壤含水量水平影响;(2)通过改变土壤水力学特性,增加土壤含水量,从而提高土壤热容量、导热率和热扩散系数。田间状态下,生物质炭影响土壤热性质的两个途径同时存在而作用相反,综合效应表现为生物质炭添加小区的土壤体积热容量有增加趋势,且与生物质炭施用量有关;生物质炭添加会显著降低土壤导热率和热扩散系数。

    Abstract:

    【Objective】Soil thermal properties, including soil thermal capacity, conductivity, and diffusivity, play crucial roles in partitioning of surface-energy and heat transmission across the soil profile and consequently affect spatiotemporal dynamics of soil temperature that determines soil micrometeorology. As a soil amendment being able to improve a series of soil physiochemical properties, Biochar has gained wide attention. However, little information is available in the literature on integrated effects of biochar application on soil thermal properties. 【Method】A two-year field experiment using wheat straw derived biochar was conducted in a field of loamy soil in East China. The experiment was designed to have three treatments different in biochar application rate: 0 t hm-2 (BC0), 25 t hm-2 (BC25) and 50 t hm-2 (BC50) and three replicates for each. A total of 9 plots were arranged in a random complete block design. Tomato was grown under drip irrigation for two seasons. Soil thermal properties, i.e. thermal capacity, conductivity and diffusivity, were measured using the heat-pluse method in two ways: (1) lab-analysis of undisturbed soil cores collected from the plots with set soil water content; and (2) in-situ measurement under natural conditions. Besides, soil bulk densities, soil water retention curves, soil pore size distributions and soil water contents of the plots were also measured. 【Result】 In soils with controlled soil water content, soil thermal capacity increased with soil water content in the range from 1.13 J cm-3 K-1 to 2.80 J -3 K-1, from 1.16 J cm-3 K-1 to 2.75 J cm-3 K-1and from 1.07 J cm-3 K-1 to 2.74 J cm-3 K-1 in Treatmenta BC0, BC25 and BC50, respectively. Soil thermal capacity was significantly decreased by biochar application in the treatments moderate in soil water content (20%~30%), whereas the effects was insignificant in the treatments low (0~15%) or high (> 35%) in soil water content. Similarly, soil thermal conductivity increased with soil water content, in the range from 0.24 W m-1 K-1 to 1.16 W m-1 K-1, from 0.19 W m-1 K-1 to 1.09 W m-1 K-1 and from 0.18 W m-1 K-1 to 1.03 W m-1 K-1 in Treatment BC0, BC25 and BC50, respectively, and was significantly higher in the treatments amended with biochar, regardless of soil water content. Soil thermal diffusivity varied in the range from 0.23 m2 s-1 to 0.45 m2 s-1, from 0.16 m2 s-1 to 0.42 m2 s-1, and from 0.17 m2 s-1 to 0.41 m2 s-1 in Treatment BC0, BC25 and BC50, respectively. Soil thermal diffusivity was significantly lower in the treatments amended with biochar either low (0~15%) or high (>35%) in soil water content, while insignificant difference was detected in thermal diffusivity between treatments moderate in soil water content (20%~30%), but different in biochar application rate. Under field conditions, soil thermal capacity was significantly higher in Treatment BC50 than in Treatment BC0, but significantly lower in Treatment BC25 than in Treatment BC0. Biochar application had significant effects on soil thermal conductivity and diffusivity under field conditions. Treatments BC25 and BC50 were significantly lower in thermal conductivity and diffusivity than Treatment BC0 and lower in soil bulk density, too. However, soil total porosity was significantly increased by biochar application, which was mainly attributed to the increase in macropores (> 0.03 mm). Besides, biochar application also affected soil water retention curves in shape and soil water content was significantly higher in the treatments applied with biochar than Control during the growing seasons.【Conclusion】 Biochar application can significantly affect soil thermal properties through the two main mechanisms as follows: (1) biochar application promotes soil aggregation, thus forming large volumes of air filled pores; and (2) biochar application alters soil hydrological properties, thus increasing soil water content and hence soil thermal capacity and conductivity. In field conditions, the negative effects biochar application brings about on soil structure are much stranger than the positive ones it has on soil water content.

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刘志鹏,徐杰男,佘冬立,李学林,王景梵.添加生物质炭对壤土热性质影响机理研究[J].土壤学报,2018,55(4):933-944. DOI:10.11766/trxb201710300388 LIU Zhipeng, XU Jienan, SHE Dongli, LI Xuelin, WANG Jingfan. Effects of Biochar Addition on Thermal Properties of Loamy Soil[J]. Acta Pedologica Sinica,2018,55(4):933-944.

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  • 收稿日期:2017-08-25
  • 最后修改日期:2017-12-08
  • 录用日期:2018-01-18
  • 在线发布日期: 2018-04-24
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