Heat Flow in Soil Treatded With Tap Water After Hot Water Treatment.

Sterilization with hot water has big effects for many soil pests and widely use in Japan.Recent years, sustainable agriculture is receiving attention, but this disinfection needs a lot of water and fuel. So it is important to decrease use of them.A technique that is possible to decrease them is additional treatment that treats tap water after hot water treatment.Change of soil temperature during hot water treatment was reported on, but it is not obvious that change of it during additional treatment.So in this study we measured changes of soil temperature from 5 to 100cm depth when we use additional treatment.We measured change of soil temperature at two plots, one is “hot water treatment” and another is “additional treatment”. Each total amount of two treatments was 185 L m^-2 and hot water was 95^oC.Rest hot water in a boiler after hot water treatment was included for tap water for additional treatment.Soil temperature at 40cm depth was under 60^oC in “hot water treatment”, on the other hand it was over 80^oC in “additional treatment”. And soil temperature at 60cm depth in “additional treatment” was higher over 10^oC than hot water treatment.As a result, we could rise high soil temperature at deep layer at site of doing additional treatment. It was caused that tap water to be used for additional treatment is heavier than hot water, so heat of hot water was transported to deeper layer.