Measurement of heat, water, and solute movement during soil sterilization with hot water
2009
Kato, T.(Meiji Univ., Kawasaki, Kanagawa (Japan). School of Agriculture) | Noborio, K. | Kita, N.
Although using hot water for soil sterilization is one of the promising alternatives to methyl bromide, there is a lack of knowledge about the appropriate amount of hot water to apply. Computer simulation is one of the methods that can easily determine the appropriate amount of hot water to be applied, but to develop a computer simulation model, it is necessary to know how heat, water, and solute behave in soil during and after hot water application. Thus, the authors measured heat, water, and, solute movement in soil during and after hot water application. Experiments were conducted in the Kanagawa Agricultural Technology Center in Hiratsuka, Kanagawa. Horizontally installed time domain reflectometry (TDR) probes (from 5 to 40 cm deep from the soil surface in 5 cm intervals) and thermocouples (from the surface to 50 cm deep in 5 cm intervals) were used. Hot water (95degC was continuously applied to the soil surface for three hours on August 24, 2007. The amount of hot water applied was 200 L/square m. Soil temperature (ST), volumetric water content (VWC and electrical conductivity were measured with a one minute interval. Values of ST and VWC consistently increased from the surface to the deeper layers. Values of ST and VWC at 5 and 10 cm increased simultaneously, so that heat was mostly transported by the convective water flow. On the other hand, at 20 cm and 30 cm, VWC first increased and was followed by ST. Therefore, the heat of the first 60 min after the start was used to raise the temperature of the soil between the surface and 20 cm, and the heat between 60 and 180 min might be used to raise the temperature of a soil layer below 20 cm. Solute in the soil was leached away to soil layers deeper than 30 cm.
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