Fundamental Study on Ozone Treatment of Soil for Agricultural Application

Abstract

In this study, influence of ozone treatment on physical properties of soil was investigated. We used a quartz container for ozone treatment of soil. The amount of soil used for ozone treatment was 300 g. Treating time was 30 min. Flow rate of ozone gas was 1.5 L/min. We measured characteristics of soil such as pH(H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O) and inorganic nutrient content (NO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> -N, NO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -N and NH <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> -N) before and after ozone treatment. Exhaust ozone concentration from the quartz container was monitored with an ozone monitor. The temperature of soil was measured with a thermo-couple during treatment. Ozone amount reacted with soil was about 0.99 g when soil was stirred. Ozone amount was about 0.82 g when soil was not stirred. Contents of NO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> -N and NH <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> -N increased by one order after treatment and subsequently kept a constant quantity. The pH(H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O) decreased drastically to strong acidic region (pH(H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O)=5.0) just after ozone treatment, which is too acidic for growth of crops. However, the pH(H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O) value recovered gradually with time.