Soil Borne Pests and Pathogens
Nematodes and many fungal and bacterial pathogens (as well as weed seeds) can be killed by using a simple method known as solarisation.
By using a clear plastic sheet to cover the top of the garden bed, temperatures in the top 6 inches of soil will raise to as high as 60 C.
This simple technique is called soil solarization and is only effective when carried out in the summer - the plastic needs to cover the soil for 4 to 6 weeks when warm/hot weather is available.
A side affect of solarization is that it increases nutrient availability. "As the soil starts to heat up, the organic matter in the soil starts to break down and after solarization, those nutrients are available to the crops, usually at higher rates than they would be otherwise.” Organic Gardening - May 2013
Step by step guide to solarisation.
1. Clear all weeds and plants for the area to be solarised. - you can solarise all or just a part of your garden bed.
2.Rake over the bed to level and smooth it, then water the soil so it's wet but not flooded.
3. Make a channel down one side of the bed. This is to take one edge of the plastic and ensures it is buried deep under the soil.
4. Lay the plastic in the channel, pushing in down in between the soil and the bed edge. Pull back the soil to secure the plastic. Make sure that the soil is smooth after you have done this.
5. Fold the plastic over the bed.
6. Pull the plastic tight over to the other edge of the bed and roll the spare plastic. Roll the plastic TOWARDS the center of the bed as this will help prevent tears when you push this edge into the soil.
Now water the edge of the bed so that it is quite wet. This will help you push the plastic down the side of the bed edge.
7. Using a thin piece of wood, press the edge of the plastic down the side of the bed edge, being careful not to split or tear the plastic.
8. Smooth the plastic out and dig the remaining 2 ends into the soil, covering the plastic to ensure that air cannot penetrate.
9. Sit back and let the sun do it's work for 4 - 6 weeks.
Thank to Denise for taking the photo's and to Lyndsay and Julie for help with covering the bed.