Water Infiltration and Temperature Movement in Soil with Hand Pan.

It is very important to find a new way of soil sterilization because the use of methyl bromide, which had been widely used for soil sterilization all over the world, has been banned since 2005 in Japan and in the world by 2010. Using hot water for soil sterilization has become popular in Japan as an alternative for methyl bromide. We investigated hot water and heat transfer in soil with a hard pan. Experiments were conducted in greenhouses. Two water application rates (204 L m^-2 and 280 L m^-2) used did not cause overflow. We found there were 2 times increasing periods of water content for both application rates. The first increase was resulted from applying water and the second one was resulted from saturated water just above the hard pan. Tilled soil became saturated with water faster than the hard pan because of larger hydraulic conductivity for tilled soil. Temperature with the water application rate of 280 L m^-2 rose twice as fast as that with 204 L m^-2 application rate at 15cm and 25cm deep. Water accumulation above the hard pan caused fast heat transfer by convection. We observed as large increases in soil water content and temperature twice increase as with the water application rate of 204 L m^-2 when water was applied with the rate of 280 L m^-2.