Can you re-use soil after harvest?

So I've got really nice FF ocean forest, and I'm close to harvest. Thinking about my next go round, could I just kind of mulch the roots and leave it in as compost for planting again? or have all the nutrients been leached out?

Separately, does anyone have experience with re-vegging moms to get clones? I'd have to cut off over a third of the stem growth to fit in my veg tent, would the clones be viable?

thanks all

its not a good idea... Kinda like would you re-eat a cheeseburger after you ate it once???

Don't re use the soil. Just replace it.

I never have...figured it was a bad idea. Think of all the build up and break down that has happened to that soil

i do. if things were good with the grow b4 then the soil is fine.. just flush it out for a couple of days really good, let it dry very well b4 useing it..

buy new soil not worth the headache later!

if all the farmers threw out soil after harvest there wouldnt be any left..... i forgot where i read it, but when i did it made soooo much sense... think about it, you can & should be able to reuse it. read up on soil mixes & figure a nice recipe for yourself to replenish your own soil. i use a mix of blood meal, alfalfa, guano, kelp, mycorrhizae, & earthworm castings

mamador1r said:

if all the farmers threw out soil after harvest there wouldnt be any left.....

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i wont go near this one, but i lol'd pretty freaking hard

i forgot where i read it, but when i did it made soooo much sense... think about it, you can & should be able to reuse it. read up on soil mixes & figure a nice recipe for yourself to replenish your own soil. i use a mix of blood meal, alfalfa, guano, kelp, mycorrhizae, & earthworm castings

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there is some truth to this. if you grind it up well (really chop those roots up) and add some ferts to it before you plant (again mix VERY well), you could probably do it. what this is doing is avoiding the actual problem that would be with reusing soil, which is a lack of nutes. also, if your plant was even close to being root bound, you may want to reconsider as well. that's a LOT of root to just leave chopped up in the soil, and i doubt it would just degrade in 2-3 months.

pretty siilly question man

Not a silly question at all. Why does having old roots in a big pile of soil disqualify it from being used again? Lots of people re-use soil year after year for outdoor. Just the other day I helped a friend dig out and till 25 holes worth of last years soil. Then to each hole, we added two garbage cans full of spyrock, some perlite, powdered micronutrients, and a couple other things and call it a day. Every year for close to ten years now, he's used the same 25 holes with the same old ass soil. Some of it gets lost from water/wind erosion but every year we add new stuff. Last year he paid some Mexicans to help and they didn't dig the holes out deep enough or till the soil well enough and the harvest suffered big time. He only pulled 80 pounds

STZ said:

Not a silly question at all. Why does having old roots in a big pile of soil disqualify it from being used again? Lots of people re-use soil year after year for outdoor. Just the other day I helped a friend dig out and till 25 holes worth of last years soil. Then to each hole, we added two garbage cans full of spyrock, some perlite, powdered micronutrients, and a couple other things and call it a day. Every year for close to ten years now, he's used the same 25 holes with the same old ass soil. Some of it gets lost from water/wind erosion but every year we add new stuff. Last year he paid some Mexicans to help and they didn't dig the holes out deep enough or till the soil well enough and the harvest suffered big time. He only pulled 80 pounds

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thank you kindly sir, for coming to my defense.

spare a pound for the poor, sir?

I like the fact that you are willing to question conventional wisdom and say "why not?" Here is my take.

1) Matter is never created nor destroyed - only moved. When you grow, all the stuff you add in to your soil has to go somewhere. Some gets absorbed into the plant material, some gets flushed out when watered and some get stored in the soil. The latter is especially true for salt based synthetic nutrients.
2) Your harvest physically removes plant material (stalk, buds, leaves, etc.). The building blocks used to make that material came from your nutrients and your soil mix. What remains after the harvest is a net delta of those building blocks that were removed.
3) The Nitrogen reserves that was present in the soil is used up during the flowering phase of the previous grow (by design).
4) Pathogens, molds, and other pests that thrive in the soil will persist after havest - some of it not ideal for growing (hence the reason to use sterilized soils).

Sooo... if you want to use the soil again, you will need to add the elements that were removed when you harvested. You will have to deal with the potential for the molds and bugs. You will also have to adjust your PH buffer as most of it would have been altered in the previous grow. All of this are possible - if - you could accurately measure and understand what was missing and replace those elements. Otherwise you run the risk of plant issues due to the missing components. Personally, I never reuse soil indoor potting soil because the cost/benefit of doing so versus the risk just does not make much sense to me.

Regarding the outdoor comparison - it is not a like for like comparison as with outdoor grows, you really do not have a closed system with a controlled in/out of added nutrients. Roots can extend well beneath the holes planted for them. The earth itself, rain, run off, etc. all mix in to even out the stores of nutrients that the plant can use. Ever see what happens after a crop is harvested? Farmers typically burn the fields and mulch it up so that that matter is broken down into something that is readily absorbed back into the earth on a macro level and able to sustain another harvest. We eat the food that is taken from the fields, and poop out the remains, which is added to the collective that makes it way back to the earth. Within a closed system, nothing is created or destroyed - just moved.

A good soil is worth saving id think but cheap organic stuff at 4-7bucks a bag isnt worth it. Unless its foxfarm start fresh.

afficionado - Thats a good point you made about molds/pests/pathogens. As long as you amend the old soil properly it should be the same (or better) than it was originally in terms of nutrient content, beneficial microbe content, drainage, etc. However, without using fresh, sterile soil, theres no way to be sure we've gotten rid of any bugs or anything that have been living in our dirt that might be bad for the plant. Also, I would never re-use soil for indoor, as its supposed to be the most sterile/controlled environment possible. Not to mention the fact that filling 5 gallon buckets for my indy room is not nearly as expensive as filling 300-500 gallon holes outside

any pics of these 25 holes? id like to see how an eighty pound harvest goes down...

nhus said:

any pics of these 25 holes? id like to see how an eighty pound harvest goes down...

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No pics of the holes per se, but here's me with one of the plants from last year. It was the largest of the crop - about 13-14 feet at harvest with upwards of 5 lbs of dried bud. Its called "Scary" its Pineapple/Trainwreck. Apparently its called "Pineapple-Garlic" in some places. This year, every single plant will be this big or bigger 80 elbows was his worst harvest since his first year Anyway, here's a shot of me standing in front of this monster plant (in re-used soil, of course) holding NorCal down.

That is a lot of MJ. What on earth would you do with all of that?

aficionado said:

That is a lot of MJ. What on earth would you do with all of that?

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what WOULDN'T you do???

I have experienced three issues with reusing soils ~ 2 are problems one is a solution if you have the space.

Nutes depleted and unused are the main prob, unless the soil is totally root bound, there will be pockets of more and/or less nutes in various levels and concentrations.

The 2n prob is the roots and the pestilence associated mentioned above.

The best and really the safest way is to use the old soil as your dirt layer in a compost pit or pile. Even a Compost drum will suffice.

I take it a step further and have a worm bed that I turn the composted soil into the worm bed. The worms breakdown the roots with natural perfection! I use the worms for fishing and the soil goes into garden ~ both indoors and out.

very interseting conversation someone brought up farmers but did not mention farmers have to rotate crops to replinish earth plant a crop of enterily different needs after a few years