Soil steaming to reduce intrarow weed seedling emergence

Steaming the soil prior to crop establishment can be a very effective method of preventing weed seedling emergence on raised beds in vegetable cropping. However, current mobile steaming technology for outdoor vegetables is characterised by an extremely high energy consumption and a low work rate. This has led to the concept of band-steaming, where only a limited soil volume is steamed corresponding to the intrarow area of a row grown vegetables crop. Weeds growing in the intrarow area are troublesome to remove by traditional non-chemical means, usually involving substantial input of manual labour in organic cropping. This paper presents the first results from laboratory studies with steaming a limited soil volume simulating a band. The investigations aimed at describing the relationship between maximum soil temperature achieved from soil steaming for different periods and effects seen on subsequent weed seedling emergence. The relationships obtained generally were sigmoid and could appropriately be described by a common dose-response function. Seedling emergence from natural weed species were reduced by 90% when the maximum soil temperature reached 61oC, and a further 10oC rise in temperature gave 99% reduction. Added and non-imbibed seeds of Lolium perenne and Brassica napus generally required higher temperatures to achieve the same control level as the natural weeds in the soil samples.