Abstract
High soil surface temperature and loosened soil are major limiting factors of plant productivity in arid and semi-arid coal mining areas of China. Moreover, the extensive and illegitimate burning of crop residues is causing environmental pollution; whereas, these residues could be converted to biochar to benefit soil quality. In this study, the effect of wheat straw biochar (WSB) at rates of 0% (control, CK), 1% (low, LB), 2% (medium, MB) and 4% (high, HB) on soil temperature at different depths (5, 10, 15, and 20 cm) and moisture levels (10 and 20%) was investigated under high soil surface temperature of 50 °C and air humidity of 40%. Our data suggested that soil bulk density was inversely, and soil moisture was directly corelated with soil thermal parameters. Moreover, the increasing rate of WSB addition linearly decreased the soil thermal properties. The maximum decrease in soil bulk density at both moisture levels (10% and 20%) was measured in HB treatment compared to respective CKs. The highest decrease in soil thermal conductivity (59.8% and 24.7%) was found under HB treatment in comparison to respective controls (CK10% and CK20% moisture). The soil volumetric heat capacity was also strongly corelated with soil moisture content (r = 0.91). The WSB treatments displayed differential responses to soil temperature. Under 10% soil moisture, temperature of LB, MB and HB treatments was higher as compared to CK at 5–20 cm depth, and MB treated soil had the smallest increase in temperature. At the 15-cm depth, the MB treatment decreased the temperature by 0.93 °C as compared to the CK20%. Therefore, the effect of WSB on soil temperature was influenced by soil moisture content, soil depth and WSB application rates. It suggested that MB treatment could be a useful farming practice for mitigating soil temperature fluctuation.
Highlights
Soil temperature is an important variable influencing a range of physical, chemical, and biological processes occurring in soil [1]
The maximum decrease in soil bulk density at both moisture levels (10% and 20%) was measured where wheat straw biochar (WSB) was applied at a higher dose (4% HB treatment) when compared with CK
The highest decrease in bulk density in our case is attributed to low density and higher porosity which favored the stable aggregation of soil particles, but some authors have warned that too many higher application rates of biochar could affect the water storage capacity of the soil [25,28]
Summary
Soil temperature is an important variable influencing a range of physical, chemical, and biological processes occurring in soil [1]. Soil temperature is a critical factor for plant growth, but it influences the soil respiration and regulates the transport of water, salts, and mineral nutrients. It is significantly influenced by soil bulk density, soil organic matter (SOM), soil texture, moisture, and air temperature [2,3]. The loosened soil is more influenced by high air temperature compared with the undisturbed soil. The maximum surface temperature often reaches 50–60 ◦C in arid and semi-arid soils [7,8]. It is imperative to investigate the impact of temperature in arid and semi-arid coal mining areas
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