can you reuse soil for weed

Reusing your soil


We are about to commit heresy and tell people that we ALWAYS re-use our soil. No soil has left the garden’s of the three_little_birds since before the turn of the millennium! Some growers will tell folks to throw out their soil after every grow, and we’ve known plenty of commercial growers that happily do that to make sure they do not have pest or nutrient problems. Maybe that even is the best solution for your grow, we can’t say for sure, as always your mileage may vary. We are poor simple medical users (and aging hippies, etc.), and spending something like $20 for a bag of FoxFarm soil rubbed us wrong! With our container system it might take 2 full bags of that soil for 3 plants!

Now again . . . someone who is involved in commercial (rather than personal medical) production might not be so inclined to bother with making sure their soils stay healthy and all the work we go through to ensure our soil’s health, but for us it is a labor of love and we feel our results speak for themselves.

Anyway, like we said, our soil never leaves our grow, it has all been recycled to the point that we could not even begin to tell you how many times it’s been through our system! A good commercial potting mix has always been the base for our soil. We look for a product which is 100% organic, and recommend that you avoid ALL chemical salt ferts like the plague if you value your soil health. This especially includes timed-released chem ferts like osmocote! Depending on what we have found for soil, we go from there. Some cheap organic soil mixes contain little more than peat, pearlite, and dolomite lime. These absolutely need amending to start off. Some organic soil mixes are much more complete and need little or no amending for starters.

Organic mushroom compost is certainly one of the hot soil mediums these days, and we’ve certainly had great success mixing it in with our soil remixes to add fresh organic matter. We can’t however comment on it’s longer terms effects in soil remixes. Since we found a cheap source of mushroom compost, we have also been top-dressing our plants with it almost exclusively, so we imagine that we will soon discover if remixing the ‘shroom compost will have any detrimental effects.

Once through it’s first grow (the plants fed 100% organic with earth juice, teas, fish ferts, and liquid kelp) our container of soil has it’s root balls pulled and it is dumped into a very large rubbermaid container w/ a lid (50 gallon container) These container’s are longer than our 2×3 growing containers, so with 2 people lifting and dumping, it’s not too hard to keep this step neat. Each bin can actually hold more than the contents from a single grow-container (2 grow-containers of soil will actually fit, but this makes mixing in amendments very difficult and messy.) Now we proceed to give back to our soil mix what our plants have taken (and then some.) We get out our kelp meal, bone meal, blood meal, greensand, rock phosphate, diatomaceous earth, and dolomite lime and get mixing. Depending on the soil’s condition this is also where we might add a little more perlite if soil compaction looks to be a potential problem.

Folks are going to ask us how much of these different supplements we add, and the only honest answer we can give is – it depends! If the plants we’d raised previously in that particular container had shown any signs of being short on a major nutrient N–P-K – it’s not too hard to throw in an extra cup or two of the appropriate organic supplement (Blood meal / Alfalfa meal for N – Bone meal / rock phosphate for P – kelp meal / greensand for K and other micro nutrients.) A nice full 16 oz plastic cup of each of the prior mentioned ingredients would be our baseline for supplementing this round of soil re-mix. We will generally double this amount if any nutrient shortage has shown. . .

The greensand and rock phosphate are very slow to dissolve and be absorbed by plants, and are not normally used by many indoor container gardeners. Their slow release is what helps to make our system work! They will still be in our soil for the next couple of grows, doing their part for our soil health. This is the point where we would also add some of our own compost (assuming there is some finished and ready – if not some mushroom compost has proven to work.) Our compost is made from the usual standards, household veggie food scraps and such, with the addition of all our used grow scraps. Fan leaf, chopped stems, and the “leftover’s” from processing by bubble bag or tumbling are all composted and returned to our soil.

Now we will wet this whole mix down lightly and let it “cook” for a spell. We have three large bins like this for soil remixing and composting. Folks always want us to be specific on amounts and times, and we do a lot of this by feel, so when we say we let the soil cook for a “spell” – how long depends on feel and need! The minimum time our soil sits is two weeks, and it’s sat waiting for use for a couple months like this during slower times in our grow. This time gives soil bacteria a chance to work and make the various organic amendments more quickly and easily available for our plants. We use this soil again for another grow, watering with our usual array of teas, Earth Juice, etc. If needed, containers are top-dressed with compost (our own or mushroom compost depending on availability) as any soil settling occurs.
Upon yet another successful harvest, the soil is reconditioned again. Once we reached our third mix of soil, we cut back on the soil amendments. The greensand and rock phosphate are still working from the last re-mix so we don’t need to add any more of them for sure. What remains in your soil at this point in terms of nitrogen and such may depend on your strain, some strains are much more greedy for some nutrients. So if our plants haven’t shown any signs of yellowing as they mature, we figure there is nitrogen enough in the soil for the next round (at least to get started – we can add more N on the fly with fish ferts and teas if needed) and no blood meal is added. If yellowing has occurred then blood meal is added again. Kelp meal is usually added again since many of the major liquid organic ferts seem a little short on potassium, and also because we like the micro nutrients kelp meal provides to our plants. Dolomite lime will probably be necessary again too, and it’s possible your soil will need even more this time than last. Any peat in the soil adds acidity as it decomposes, and the lime balances this as well as providing magnesium. After the standard 15 – 30 days of standing moistened waiting for use this soil is used still another time. Now our soil has grown 4 crops of herbs and is still going and growing strong. At this point, we have started plants in our soil remixes directly alongside plants in fresh potting soil, just to make sure our mix wasn’t subtly stunting our plants.

The plants grown in our 4th and 5th generation soil remix did far better than those directly alongside grown in fresh from the bag FoxFarm OceanForest potting soil! Because our garden is a continuous harvest setup, once we are to our 4th or 5th remix, it’s starting to get hard to keep track of exactly what soil has been remixed where, since half used bins of remixes are often dumped together to make room for another round of used soil coming from the garden. So we simply continue adding amendments by feel as needed.

This is how the three little birds use soil. We know we break the rule we have all been told to follow – to never reuse soil. Even those “radicals” we have seen reusing soil, have always described letting their soil go out to their veggie gardens or flower beds after 3 or 4 grows. We decided to push the envelope and see how far we could take it . . .
We still haven’t found a limit for the number of times we remix our soil, and our harvests and plant vigor keep improving.

Oh, just to add another bit of heresy, you may have noticed our container grows suspended above the floor on wheeled furniture movers. It’s a very convenient way to keep the plants in larger containers mobile. . . but you also must realize then (if you think about it) that out grow containers have NO drainage. Our soil mix, which is now has been remixed double digit times, has NEVER been flushed! We warned you all at the start of this post that some might consider it heresy . . . And we can’t even begin to tell you how we can break these rules and get better results than average – but it works for us and we wanted to let folks judge for themselves.

one thing we might add – we certainly would not remix soil from any containers where we’d had a bug or disease problem – even getting bud mold would be enough for us to say – no thanks to a soil remix

we were discussing this among “the birds” the other nite – and one line that a little bird said comes to mind . . . “Farmer’s don’t strip their topsoil after a harvest – or even a few – in fact their soil is their most precious commodity – why should it be different for indoor gardening as long as proper care is taken to build healthy soil?”
Last edited by 3BM : 03-24-2007 at 05:50 AM.
Microorganisms are part of the decay cycle, which serve to break down organic compounds and combine them into more complex forms (like vitamins, enzymes, amino acids, etc), and make them more readily accesible. Beneficial bacteria, fungi, nematodes, and many others are all part of this system. Having an active soil is the halmark of good organic gardening. Mature compost is the best source of bio-activity you can get. I recommend making your own pile, for more detail on how to start one check out the thread “A Compost Guide”. Municipalities sometimes create compost with leaf and grass waste which can be purchased locally for low cost. Barring that composted manure, mushroom compost, and Earth Worm Castings are all available at garden retail locations and will work well to populate a mix with microorganisms. Many of these organisms are present in the air so that just adding organic matter to soil will soon yield colonized soil. I recommend adding organic matter (compost, manure, EWC) and then letting the soil sit for at least 2 weeks, but better yet 4 weeks. Reusing soil will ensure that every bit of your mix is well colonized.

For the basics on remixing soil, check out the thread “Organic Gold: Soil Heresy”. You should start with a quality wood fiber based potting soil (like Fox farm Ocean Forest, or Shultz’s Garden Safe, or even Miracle Grow Organic Feeding Formula). Use only organic slow release nutrients to supplement this soil (like compost, manure and EWC). Finally, choose a slow release source of N, P, and K. Check out Rainbow mix or FF Peace of Mind for pre-mixed NPK w/ added microorganism innoculants (in this case its fungus). Also check out the Earth Nectar (EN) product as a great soluble source of bacteria, fungi, and nematodes. Bear in mind that any microbial innoculant is probably just a take off of good quality compost, so save your self some money and start composting ASAP. Read through the Organic Gold threads (there are 4 maybe, you may have to go back a few pages to find them all), as they will get you started on soil life and soil remixes (including what amendments to look for). I hope this helps.

My thinking says adding POM starter mix and POM fruit and veggie, dol. lime, Maxicrop liquid, Earth Nectar and Earth Ambrosia, possibly more perlite would revive the mix. Any comments?

Adding the mentioned amendments is a good start. Also think of some long term release sources also. I liked working with different release times for the same nutrients. Inoculate the substrate with a good microbial tea and let nature so its thing. I generally use EWC, Molasses and tepid water to make a tea and add it to the bin.

There’s a number of ways that soil, or soiless can be reused in your grow. If you are all organic, it’s easiest to shake the roots out, mix the old with the new in a bin, and let’r sit for a month to establish a great microherd. There have been a number of great suggestions in this forum, but one thing I would never do is use my compost in an indoor mix. Yes, it does have a superabundance of micronutrients and a fully established microherd. It can and will also bring in the nasties you don’t want, and aren’t set up for indoors. Why bake or microwave? This just kills everything good that organic farming needs, and you must re-establish your microherd. Most folks have room for a few 6-12 gallon totes. Just keep adding and mixing your old with your new, and let them sit for a minimum of a month to establish the herd throughout. The beauty of organics IS the microherd. The ability to utilize nutrients and micronutrients that your plants may not be able to “eat” without the herd. Protection against many of the problems associated with “chemical” ferts goes away. Stronger plants with more stress resistance, pest resistance, drought resistance, increased production, color, aroma, flavor, you name it. I started 6 years ago, and havent looked back since. You can get as creative with your mixes/or nutrients as you want, but keep them organic and establish a microherd to make them available to your plants. Your soil level goes down everytime you run again due to the uptake/absorbtion of nutrients, and the natural decay/compost of the soil/soiless matter in your mixes. I havent thrown any mix out in 4 years. It’s all in the flavor, colors, and your head. Good luck
The measurements recommended are from 16oz dixie cups. A full 16oz cup = 2 cups. I typically add 2-4 full dixie cups per 45 gal of dirt. I mix my dirt in large (55gal) rubbermaid tubs. I keep them less then completely full to make mixing easier. Just use a high N fertilizer (Mex Guano, Blood Meal, Alfalfa meal) at 3 scoops/45 gal, then use a high P fertilizer (Indo/Jam Guano, Bone meal, Rock phosphate) at 3 scoops, and finally use a high K fertilizer (Kelp Meal, Greensand, Composted Wood ash) at 3 scoops. Mix all this very well into a good potting soil (ProMix BX, FF Ocean Forest, BioBizz, or just composted top soil from a garden) and let sit for at least 2 weeks.

To give a quick example. Lets assume I am starting from scratch with choice ammendments on hand to begin with. I get the following ready:

1 bale ProMix BX (or 3 bags quality potting soil)
1 30lb bag Mush Compost
1 30lb bag Worm Cast
1 large bag Perlite
1 small bag play ground Sand
1 3lb bag greensand
1 small bag Mex Guano/Alfalfa meal
1 small bag Rock phosphate/Indo Guano
1 15lb bag Kelp meal
1 small bag dolomitic lime

I add 1/3 of the ProMix bale to a 55 gal rubbermade container, and to it add the compost and the worm cast (both bags). Then I add 3lbs of green sand and 3lbs of playground sand. Next I add enough perlite to ensure adequate aeration (usually 3 gal or more). Mix thoroughly by dumping this mixture into an empty identical rubbermade container, and then repeat. Finally add 2 full 16oz dixie cups of Mex Guano (or 3 of Alfalfa meal), 3 full cups of Kelp meal, 3 full cups of rock phosphate (or 2 of Indo Guano), and 1.5 scoops of dolomitic lime. Mix thoroghly by dumping back and forth, and VOILA! completed soil mix. Add 3 gal of water (from the tap is fine) and cover for 2 weeks AT LEAST. The longer the soil sits the more available the nutrients become. After 2 days of sitting moistened lift the lid and plunge your hand down into the soil. It should be very warm. This is why you must wait 2 weeks, that much heat can kill seedlings and damage roots.

This is the quick and dirty version. Reread the original article for more specifics on the ferts (how and why they work). Also remember that this mix is intended for repeated usage. Many of the elements added will continue to be effective over subsequebt remixes. To reuse the dirt, simply pull the rootballs and start over adding what the plants have taken away. The greensand and rock phosphate are particularly long lasting, so do not add as much in remixes. I cut them way back, or dont add them at all for several remixes. Also, check the pH after the soil sits and add more lime as necessary. Any peat in the mix will become increasingly acidic over time so checking the pH and correcting with lime are keys to soil success.

I hope this answers your question. All of this advice is based on sound organic gardening and would work with any plant you choose to use it on. You could just dig soil out of your garden (assuming its organic and productive), but I like to compost it before bringing it inside. A high heat compost will kill any weed seeds or pathogens remaining in the dirt. You can also add the nutes listed above to the compost mix to get a head start on making them readily available. Good luck and happy experimenting!

Organic Gold III – Soil Heresy by 3LB soil heresy by the 3LB ~ CW We are about to commit heresy and tell people that we ALWAYS re-use our soil. No soil…