Abstract
Soil thermophysical properties are the key factors affecting the internal heat balance of soil. In this paper, biochars (BC300, BC500 and BC700) were produced with wheat straw at the temperatures of 300, 500 and 700°, respectively. The effects of biochar amendment at the rates of 0%, 1%, 3%, and 5% on the thermophysical properties (thermal conductivity, heat capacity, and thermal diffusivity) of a loessial soil were investigated with and without water content respectively. Although the bulk density of soil significantly decreased with biochar amendment, due to enhancing soil porosity and organic matter content, the thermophysical properties of soil did not change largely with biochar amendment rate and pyrolysis temperature. Water content exhibited significant effects on the thermophysical properties of soils added with biochars, where the thermal conductivity and heat capacity of soil were linearly proportional to water content, the thermal diffusivity initially increased and then decreased with the increase of water content. In the meanwhile, there was no significant correlation between the biochar amendment rate or pyrolysis temperature and thermophysical properties. The results show that water content should be mainly concerned as a factor when the internal heat balance of loess soil is evaluated, even though the soil is amended with biochar.
Highlights
Biochar is a solid carbon material obtained by the pyrolysis of biomass under high temperature and a limitative oxygen condition (Ding et al 2016, Tripathi et al 2016, Li et al 2017)
Usowicz et al (2016) noted that there was no significant change in soil thermal conductivity and thermal diffusivity after application of biochar in grassland, while in fallow land, both of them decreased with the increase of biochar amendment
The changing laws and mechanisms of wheat straw biochar influencing the thermophysical properties of loessial soil were explored
Summary
Biochar is a solid carbon material obtained by the pyrolysis of biomass (such as straw, sawdust, sludge, etc.) under high temperature and a limitative oxygen condition (Ding et al 2016, Tripathi et al 2016, Li et al 2017). Biochar could be a modifier to improve the fertility of loess soil and enhance crop yields. During the crop growing season, the albedo of soil treated by biochar decreased by 20-26%. Usowicz et al (2016) noted that there was no significant change in soil thermal conductivity and thermal diffusivity after application of biochar in grassland, while in fallow land, both of them decreased with the increase of biochar amendment. There have been few studies on the effect of biochar amendment on the thermophysical properties of loess soil. The changing laws and mechanisms of wheat straw biochar influencing the thermophysical properties of loessial soil were explored. The results could provide a reference for the subsequent evaluation of the physical environmental effects of biochar on loess soil
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