The process takes approximately 25 - 30 minutes, but with perseverance over several weekends and evenings I soon had sufficient sterilised materials for the entire season. The pictures above show the steam sterilising unit. The bucket sits on top of a pan of water that is heated using a conventional electric element. The steam finds it's way through the perforated cone that forms the base of the bucket and onwards through the soil. The lid for the bucket has a small hole in which a thermometer is inserted to keep an eye on the soil temperature.
Sterilisation is complete when steam emerges from around the lid on the top of the bucket.
By this time the soil temperature will be approaching boiling point. The soil is then spread out on a cold surface and cooled as quickly as possible before bagging and storing for several weeks, after which it is ready for use. Sterilisation is not without it's complications. There can be adverse effects related to soil sterilisation so a little research was required to make sure that only the beneficial effects were transferred into the growing routines. For instance, experiments have proved that lime added after sterilisation is far more beneficial than when added before, similarly superphosphate is added after sterilisation to counter the retarding effect of excessive ammonia produced during the steaming process.