Variation in soil thermal properties under different soil solarization materials varying in thickness under field conditions in Nigeria

An in-depth knowledge on the soil thermal properties under different soil solarization techniques is essential for soil treatment against soil-borne pathogens. This paper presents an investigation on effects of different soil solarization materials on soil thermal properties, organic matter and aggregate stability under field conditions. This study evaluates three materials: translucent whitish plastic (TWP), transparent nylon (TN) and black nylon (BN) each at three thickness levels (0.05, 0.10 and 0.15 mm) and control (bare soil). The parameters investigated in this study included soil temperature, organic matter, bulk density, volumetric moisture content, thermal conductivity, volumetric heat capacity, heat flux, thermal diffusivity and thermal effusivity. The results showed that the soil solarization materials varying in thickness influenced the soil heat energy transfer and had a significant effect on soil bulk density and volumetric moisture content. The results revealed that transparent nylon at a thickness of 0.05 mm recorded the highest soil temperature (62oC) and was significantly higher than black nylon at a thickness of 0.15 mm (44oC) and the bare soil (41oC). Transparent nylon at a thickness of 0.05 mm also recorded the highest organic matter content (19.60 g kg-1). The bulk density of the bare soil (1.57 Mg m-3) was significantly higher than the bulk densities of soils covered with solarization materials. Transparent nylon at thickness of 0.05 mm had the highest volumetric moisture content (0.116 m3 m-3) while translucent whitish plastic at a thickness of 0.15 mm recorded the lowest (0.401 m3 m-3). Transparent nylon at a thickness of 0.05 mm transmitted the highest quantity of heat through a unit length of soil per unit cross-sectional area (2.50 W mk-1). The variation in volumetric heat capacity between the solarization materials was highly noted in transparent nylon (TN) at a thickness of 0.05 mm (2.65 J (m3K)-1) and less in bare soil (control) with a value of (1.65 J (m3K)-1). Transparent nylon with thickness of 0.05 mm transferred the highest heat per unit area of soil (42338.25 W.m-2), while bare soil transferred the lowest. The highest thermal diffusivity (1.35 m2s-1) was recorded in the soil with no solarization material. The soil under transparent nylon with thickness of 0.05 mm recorded the highest exchange of thermal energy (2.57 Jm-2 K-1 S-1/2) with the environment and was significantly higher than other solarization materials. The transparent nylon had the highest soil macro aggregate stability. This study will help farmers in terms of choice and adoption of affordable conservation methods in treating the soil against soil-borne pathogens.