I had a tomato seedling 30cm high growing in potting soil in a large pot, but the pot had no drain hole so the water built up and went sour. I have replanted the tomato into another holed pot, but am left with the old smelly sour potting soil. How can I rejuvenate it or must I throw it away?
Best is to trow it away, potting soil is usually meant for one time only. Especially for growing vegetables and crops; the nutrients in fresh potting soil lasts normally only a few weeks. So this means that you need to fertilize after a few weeks for nice crop. My advice is to find a place where they sell cheap potting soil, so you would never have to reuse old potting soil gone sour.