| Trudi, if I may jump in here. Questions often come up regarding solarization. It's used too little for effective weeds and pathogen control, but the opportunities for failure are high. Black plastic, as mentioned earlier, is not effective (at all) in solarization. The heat is absorbed by the plastic, which will then merely warm the upper surface of the soil. Sunlight must penetrate deeply into the area in order for solarization to occur. As a matter of fact, you want to use the thinnest grade of clear plastic that you can find. Other factors for success include: ambient temperature, number of days with sunshine, type of soil, depth that soil was tilled, proper preparation of site, and the correct installation of plastic. Yes, 'proper' solarization will kill many soil pathogens and weed seeds, but temperatures must reach at least 122o F for the most stubborn. Many are not that difficult to kill. Pathogenic bacteria, fungi, and virus are all susceptible, as long as they are soil borne. Also, if you turn under a crop of (say) diseased tomatoes, a thorough solarization process will kill those pathogens. Nematodes are steamed out readily. Beneficial (and essential) microorganisms are killed in the process, too, but it appears that they are able to rebound rapidly, while the pathogens are not. Earthworms, of course, are able to move out of the area or go deeper for the duration. In locations where solarization has proven essential to raising agricultural crops, the fields 'take turns' in being put out of production so that the 50 or so days of beneficial steaming can occur under that plastic. I hope that I've answered your questions and also hope that I haven't been presumptuous in doing so. |