sterilizing

Up until this year I had never heard of sterilizing potting soil,planters or any of the other things one is supposed to do while gardening. Just how important is it? Can one really see a difference in the way their garden looks, lets say the sterilie side as to the unsterilie side? I know we all have our little qurts or quims as to what we do in order to grow vegetables. If I thought it would make any difference at all I would sterilize my whole garden which is about an acre. I am sixity eight years old retired and have too much time on my hand also I love to garden and dig in the dirt and will try anything once so as of right now I have two coffee cans on my electric grill cooking, or should I say sterilizing the potting soil. If it will get rid of the southern fungs,black leaf rot, or whatever the name is of that stuff that is killing my tomatoes every year I will jump out of an airplane at thirty thousand feet and free fall with a bag of potting soil.Well maybe not quite that extreme. Really though I will disinfect my greenhouse sterilize my potting soil and boil my plant water to stop my tomatoes from dying. Hey I had not thought of boiling my water. Think all that those additivies have an effect on the plants. I will use only rain water from now on. I have fifty gallon plastic containers at each corner of my house to catch water to use during dry spells.
All of these words just to ask how important is it to use sterile potting soil?