The performance characteristics of the sterilization of raised beds by steam applied from the surface

Abstract

The partial sterilization of soil in raised beds in glasshouses is frequently carried out by a method known as sheet steaming. Some measurements taken during the routine steaming of six beds show that the depth of heat penetration by this method is variable. At a depth of 2 in (51 mm) the process was consistent, but at a depth of 6 in (152 mm) the process was less reliable, there being a reduced rate of heating and lower soil temperatures. During the 5–6 h duration of the treatment up to 2 1 2 times more steam was supplied than would be required with a steam injection method such as Hoddesdon pipes. An initial steam supply rate of at least 3 lb h −1ft −2 (4·07 g s −1 m −2) of bed should be allowed.