How to mix not so good soil with good soil?

[plantingplants]

If you had a 1.5 yard pot of $60/yd soil (nutrified redwood, perlite, pumice, greensand, probably some other organic matter, and some other stuff I can't recall but it's just a basic soil for chemical ferts) that was used for one short season and small plants, and you just got one yard of really good soil like cootz', what would you do?

I was thinking I would leave 0.5 yard of old soil at the bottom of the pot, stir it up real well, and add the yard of good soil on top, mixing it just a little bit so there isn't a sharp dividing line between the two.


....or would you just amend the old soil with a cootz like formula? Besides the nutrient amendments I'm not sure how to figure out how much peat or compost to add to this old soil. Is there a way to tell?

 

[_tessarecting]

Well, ideally, you would lab test old soil, ammend to the requirements, then add the new soil that has been tested and balanced too. You could also wait to ammend once its in the pot to make working it volume wise easier. You never want to just roll the dice.

 

[green-genes77]

I would avoid using the old soil without first flushing and sterilizing it. Even after being used outside in the short term the media could have an accumulation of fertilizer salts, resident larvae, bacteria or detrimental fungus. The pH and nutrient concentrations have to be treated as unknowns too. Use new soil every year if you grow in containers.This is my advice as a horticulturalist.

However, I know what it's like to make things work with what you've got. Inspect the old soil with care and at bare minimum flush it thoroughly. Go with your idea of using the old stuff in the bottom and filling the rest with new, but amend the old stuff lightly before filling your pot by adding some slow release ferts (go light on the nitrogen) and additional perlite or sterile pebbles or chunks of styrofoam or whatever you've got to aid drainage and enhance gas exchange in the roots.

 

[plantingplants]

Thanks, yea I don't know much about amending which is why I'm buying fresh soil already amended for me I don't want to make a mistake but I can handle adding some pumice to the bottom soil.