Bacteria can sometimes strike a plant and cause diseases that can weaken and kill the plant. This is often a problem when the soil was previously home to a plant that was attacked by harmful bacteria. The soil can be treated using heat, and ideally, pathogenic bacteria are wiped out. These treatments also kill weeds and their seeds.
Soil is treated in order to kill harmful microorganisms that are found in the soil in order to keep the plants that are planted in this location happy. These types of treatments are especially important for transplanted plants, since these plants will be particularly vulnerable and will not necessarily be able to handle a high level of microorganisms in the soil. Keeping the number of microorganisms down to a low level is possible by buying sterilized potting mix or by cleaning the potting mix. Gardeners do not want to completely sterilize the soil because sterilization cause disease-causing organisms to flourish, since harmless bacteria that would compete with the disease-causing bacteria are killed off.
Before treating soil, the soil must have a crumbly texture and must not have large chunks of plant matter in it. The soil must not be treated before soil conditioners or amendments like manure, compost and peat moss are added. Treating the soil is pointless unless the soil has enough moisture for seed germination, but it should not be so moist that it forms a ball in the hand that doesn't crumble. The temperature must be 60 to 65 degrees Fahrenheit. The container and tools that are used with the treated soil must be sterile, and plants added to treated soil should be disease- and bacteria-free.
According to Washington State University, the soil that is going to be treated can be moistened in order to get weeds growing, which makes them easier to kill through the treatment process.
Soil can be treated using an oven, a steam-based cooker like a pressure cooker, or through fumigation. Fumigation is a gas that is added to the soil and kills most of the bacteria that would harm the plant. Fumigation should not be used unless the soil is in good condition.
The soil must be kept at a temperature of about 160 degrees Fahrenheit for 30 minutes in order to kill the worst bacteria and some of the weed seeds. Some weed seeds require higher temperatures in order to kill them, but these higher temperatures can over sterilize the soil, killing beneficial bacteria.