Would you use grow op soil on your property, and how?

I have access to a lot of used marijuana growing soil + roots (weed growing is probably the biggest industry in my area) which is mostly peat moss and a LOT of perlite. I think the white perlite looks ugly, I hate the way it floats to the top when I water and makes the soil look white. There were definitely lots of fertilizers used, and I'm sure it was sprayed at some point too. I've used some mixed into my containers and houseplants, but I'm hesitant to put it in the ground or use it in raised beds, both because of chemicals used, and the ugliness factor.

Can anyone tell me if using it will be a benefit to my crappy soil, and how you would use it if you had it?

I've got lots of experience with this stuff too, it is the big industry around here as well. If you can verify that the soil came from an organic operation (they do exist, although they are usually less likely to be getting rid of their soil) then there are absolutely no downsides to it. Perlite is gross in its production but is ultimately a 'natural' product in that it is simply specific rock subjected to an industrial 'jet puffing' process. The soil will definitely help to loosen clay soils if tilled in and, as it is typically a neutral media, it can be great as a seed starting mix. I have used it primarily as a compost additive though. I find that my kitchen compost is far to wet to compost well on its own and since we are in evergreen forest we don't have the dry leaf litter that is a great remedy for that. With a few trashcans of old grow dirt on hand I can mix this super dry and absorbent stuff with my soggy kitchen scraps and make a good compost consistency. The other thing you can do with it is mix it with finished compost to make a wonderful container soil. To me, the primary question is the practices of the farm it came from, if you are getting it from a chemy farm then you are just importing chemical residues that you probably don't want to your land. If you are getting it from an organic operation than you are just importing organic matter that is great for loosening overly dense soils and increasing drainage but that would never be economical to buy yourself. You are right about the perlite but really most of the weed soil is coco coir and perlite and some peat. There is also often a serious excess of phosphorous because it is not used as fast as people think (the flower to leaf ratio on my borage is preposterous).

Thanks Stephen :)

They called their operation organic, I just don't know how organic it can be. Definitely way better than the industry standard though.

I have mountainside loamy soil (i think) with lots of rocks and practically no organic material. It already drains well, I don't think I need to improve that aspect.

Maybe I'll use it as part of the soil in my future greenhouse, and keep using it in containers. I've also used it in my seed starting mix.

I think you got it then, I would also recommend using it in compost. If it has lots of rootballs then those roots are very mineral rich. One reason I love getting used grow soil when I can get clean stuff is that marijuana is a high value crop and as such the growers tend to spend lots of money mineralizing their soil (assuming they know what they are doing). So you can basically get a whole lot of expensive inputs for free when they give away their 'used' soil.

Maybe spraying the soil with lactic syrup or some sort of mycorrhiza inoculator would help with breaking down the roots and other organic compounds.  

I would double dig this top soil to existing gardens and let it mature with fish hydrolysate and lactic bacteria cultures.

stephen lowe wrote:I think you got it then, I would also recommend using it in compost. If it has lots of rootballs then those roots are very mineral rich. One reason I love getting used grow soil when I can get clean stuff is that marijuana is a high value crop and as such the growers tend to spend lots of money mineralizing their soil (assuming they know what they are doing). So you can basically get a whole lot of expensive inputs for free when they give away their 'used' soil.

Good point, I didn't think of it that way!

If I were going to use it, I'd first put it in a hot compost pile and cook it at 150 degrees for 3 weeks --- classic Berkley method composting.  I'd use a lot of comfrey and coffee grounds to heat the pile up, and then I'd turn it every 3rd day until the temperature begins to drop below 120 or so.

If you're still concerned with residual chemicals, you could then mix that compost with wood chips and let it sit for a year so that  fungi have a chance to multiply and do their remedial work.

I'm curious: why are they throwing it out?  Why don't they just recharge it with new compost and fertilizer?  If they are using chemical fertilizers, then why wouldn't they just re-use the same soil again and again?  Once you douse living soil with Miracle Grow, whatever microbial life that used to live in the soil gets fried, so they might as well just keep using the same growing medium.

I'd take it and process it as I described above, and then it'll be great to use in raised beds or containers in a year.

Thanks Marco, that sounds like a good idea to make sure nothing nasty remains.

Buying new soil for each run of plants is common practice here with indoor growers. I'm not sure exactly why, but I haven't heard of anyone growing on a larger scale reusing their soil. I believe this particular mix is called Promix Mycorrhizae which I assume is inoculated to some extent. This grower claimed to be organic, but I doubt that's the same as your organic or mine. They still feed the plants tons of products, and I don't know what they do for pest control. I guess the nutrient products they fed were organic.

A relative of mine works in a medical Marijuana facility. They do not use soil at all. They use a "grow medium" which is made from an assortment of material.

This reminds me of the residue left over after growing mushrooms. Why is there such a big difference in what's used. With mushrooms they use manure, steam it twice and I would assume there's some composting, intentional or otherwise. But seems to me one would check both industries before relying on one. I used to hear rumors that the mushroom industry gave away their output. But what I remember is that they gave preference to the bigger trucks. A guy with a pickup or small dump truck might wait... a long time. But that was rumors and old ones at that. Do they grow mushrooms in your area??

You might prefer one over the other, or a mixture of the two.

The last time I bought mushroom manure it was $35 a cu yard. I was quoted $31.50 this spring, but didn't spring.