I've been reusing some of the same soil I started with over 11 years ago. The people who push the " Just Say No to Reusing Soil " are the guys wanting to sell you new soil every grow. IMO that's a complete waste of money.
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Let's be honest, do farmers or even home gardeners, avoid using the same soil to grow new crops, of course not.
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Take the soil from your finished grow and put it in a compost barrel, add browns & greens (leaves & grass clippings), left over kitchen waste (no dairy, meat or spicy foods), moisten & turn weekly. Throw in a cup of High Nitrogen Bat Guano or three cups of Rabbit Manure to keep the tribe of micro-beasties alive & kicking. With a source of N, they will reproduce & bio-convert all the insoluble NPK in the left over soil into soluble NPK, plus make the soil more friable.
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In 14 to 28 days, if turned weekly, you have a good base to mix your own soil for the next run. Use this compost as follows: New soil mix : 50 percent compost you just finished, 30 percent peat moss or well rinsed coco coir, 10 percent perlite, and 10 percent worm castings.
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This mix will be mellow enought to start seedlings in with no risk of burning.
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Then feed your plants later using wholesum organic fertilizer teas : Read - Making Tea is E-Z & cheap thread......
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There is not reason to ever scrap used soil, it can & should be recycled indefinately - just like in nature.
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Hope this helps....
Keep it Real....Organic......
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