We just had a discussion on this topic and a wide variety of opinions were expressed but no there is no reason to add soil to the compost material. Once it was thought that putting good, rich soil on the material to be composted would add the bacteria that would digest that material. Today we know that all of the material we put into be composted already has the bacteria that will digest them in place, that is why the foods left out develop the fuzzy stuff on them. Mycorrhiza refers to a relationship some fungi have with plants and not to any specific fungi. That relationship is most often symbiotic, mutually beneficial, in that the fungi get sugars from the plant in exchange to providing necessary nutrients to the plant. Mycorrhiza is not a specific fungi that you can add to soil or compost no matter what the sellers of products may tell you. Each plant develops this relationship with different fungi.

Hey, I will try to answer as thoroughly as possible. I grew 96 plants. 4 types. 24 peas, 24 basil, 24 lettuce and 24 radish. My project is dealing with utilizing the nutrients in sanitized waste. So basically I collected compost and used it in different concentrations with potting soil. 8 trials (2 x 4 types of plants) with 100% compost, 8 with 80% compost, 60%, 40% and 100% potting soil. I then watered some with just tap water (with very low concentration of nitrogen, ammonia 0.06 mg/l and nitrate I sent the soil away to be analysed and before the soil contained 326 mg/l nitrogen and I fertilized with 100 ml of 51 mg/l nitrogen (from the urine) 6 times before harvest. The resulting soil after harvest contained 205 mg/l nitrogen (almost all in nitrate form). What I am curious about is the chemical fertilizer trials. They were planted in a 80-70-160 potting soil and given the fertilizer 51-10-43 watered 6 times with 100 ml each time. The resulting soil test shows 10-13-30. It seems strange for it to be so low. Did the plants really take up that much? The % of dry material from the plants show 2.1-0.33-2.0. Does any of this make sense? There was no urea present because the urine had been stored in air tight containers for 3 months prior to using. The temperature of the greenhouse was a steady 19 degrees C during the day and 15 at night. It was all automated. And albert_135 I didn't really prevent loss to drainage, how would I do that? I will comment in my discussion section about that though, possible sources of error. And no I didn't water pots with no plants, that would have been a good idea. But it is so expensive to have the samples analysed so I was trying to keep costs down. The results didn't give a range, just the plant samples which was +/- 15%.

Thanks, everyone!! I think I will go with the green bin approach, since I worry that the perlite will just blow around and be a bother around the building. It already happens in my pots! Funny how it seems to end up on top, I guess bc it's lighter. Since the balcony gets so hot, I think the soil just gets baked into oblivion and I don't feel comfortable reusing it in my pots, no matter what else I put in. Just out of curiosity... how does it get composted by the big composting outfits? Is it that it gets put in with such a large amount of actual compost in the making, that the fact that the structure has been ruined gets so diluted that it doesn't matter anymore? Maybe it somehow reclumpifies or something?

I've tried shredded paper and cardboard, and unfortunately it won't work for this particular bit of mad science (though it has made decent worm bedding in general). I've got four problems, and I'd like to try to engineer a device to help with all of them. (1) Very poor soil for the garden, (2) miniscule income stream, (3) too many cats generating waste, (4) no energy left after dealing with the kid and the cats and the garden all day. I've had an idea that just won't leave me alone, especially after I had to chase a kitten off from trying to piss in my worm bin. I want to create a worm-powered, self-cleaning litterbox. Tentatively it will be the size of a tall kitchen trash can, and it will use a flow-through design. Every few days or as odors arise, a new layer of bedding will be laid down on top. As needed, I will harvest processed fertilizer at the bottom. I hope to use freebie materials like dumped wood chips for this, but right now they're not available. I tried shredded paper products in the normal litter box, but the cats didn't take to them very well. The other day I put some spare potting soil in the litter box out of desperation, just trying to get through till pay day, and the cats seem to like it a lot. It's not free, but it's cheaper than cat litter, I wonder if I might have a short-term winner here. My concern about the carbon content is largely one of buffering capacity. Cat pee and poop from this many cats is a heck of a lot of nitrogen, and I don't want to burn up the worms, poison them or otherwise wreck the system.