Water Content and Temperature Distribution Under Hot Water Infiltrating Condition into Greenhouse Soil.

It is very important to establish an alternative method for soil sterilization in a greenhouse because the use of methyl bromide, which is a major chemical used for soil sterilization all over the world, has been banned since 2005 in Japan, and will has been since 2010 in the world. We focused on soil sterilization using hot water, which became popular recently in Japan. However, because using hot water for soil sterilization is quite new, few studies have been conducted. Using hot water for sterilizing a greenhouse soil is beneficial to farmers because it is very ecological, low cost, safe for human health, and leaching excess chemicals. Not only advantages has the new method, but it also has disadvantages if we use it in a wrong way. For example, excess heating water wastes money and excess infiltrating water into soil may pollute groundwater and decrease the amount of minerals in the soil. Consequently, we need to find out suitable amount and temperature of hot water. The goal of this study is to understand heat and water movement during the hot water sterilization in the field. The temperature of hot water was 95 degree Celsius when it was applied to soil in a greenhouse. A plastic sheet was used to cover the soil surface for decreasing heat loss from the ground to the air. Thermo couple thermometers and time domain reflectometry probes was used for measuring temperature and water content in the soil profile, respectively.