I have never baked or done anything to sterilize my potting soil before using it for my own purposes, and I have never had any real problems. I think for the most part it is sterile when you get it. In college I remember using steam to sterilize soil that we were reusing in the greenhouse rose beds...but that was because it was used:) I know that a lot of people do use special seed starting soil mix, but I always just use Pro-Mix potting soil. I;m sure some folks will tell you to use seed starting mix, and others will say it doesn't really matter (like me!), but what it comes down to is what you personally prefer. Why not try a little experiment and start some in the finer mix and others in regular mix...and see if it makes a difference to you! I just find it easier to use one kind, and I buy the huge 3.8cu ft bails.

Hmmm. No one ever talks about the microbes. Microbes make top soil unique - definitely not the same as sub soil. Microbes act as the interface between the organic material in soil and the plants. Plants will suffer in sterile soils, not matter how rich the soil is, without microbes - unless of course, the soil is treated with synthetic fertilizers and/or hormones. Plants in soil without microbes (and no fertilizers) will essentially starve. Dirt is not an appropriate synonym for top soil. The two are quite different things. Top soil is almost impossible to store, as the microbes require oxygen. The oxygen only penetrates a few inches in the best of soils, to about 8 inches max. Heavy soils can have top soils that are only fractions of an inch deep, or even none at all. Deprive the microbes of oxygen, and the microbes die in hours. Plastic-bagged, manufactured top soil, will not have appropriate conditions for microbes to survive if they were ever present. Even true top soil, if harvested through grading and stored in piles, will only be true, healthy top soil on the top few inches of the mound. Within hours all of the microbes below the top layer of the mound will have died. True top soil is a living thing. Top soil needs to be harvested and properly placed in a very short period of time. Take a yard of dirt (or at least a good pile) from below the top soil, mix it with fertilizer-free compost, mound it up in a remote area of your yard and watch what happens - nothing. Nothing will grow on that pile, even though it is dirt amended with compost, because it essentially sterile. After one to two years, the microbes will begin to permeate the top layer of the pile and plants will start to show up. With true top soil, the mound would explode with plants after the first rain. Manufactured mixes "cheat" by stuffing the created mix with fertilizers. This works, but is lousy for the environment in many ways, and "hooks" your plants on synthetic fertilizers like drugs. When you hear such names as Monsanto, Miracle Gro, etc. think "pusher". Microbes do not like synthetic fertilizers, so once using fertilizers, you are stuck using them unless you do a lot of work to fix the situation, or wait until the soil regains a proper ecological balance. Plants will grow well in many types of media, even water, if given proper aeration and proper nutrition, i.e. fertilizer. But this is needlessly expensive and again, potentially problematic for our environment. True top soil is magic. It's ecology is wonderfully complex and is only barely beginning to be understood. No manufactured mix will do what true top soil can do for your garden. Growing plants really needs to be thought of first as growing your soil. True top soil, air, and water are vital to most life forms on Earth. We would all starve without true top soil, unless we were able to subsist on fungi. Labeling requirements for growing mixes are virtually non-existent. Those ingredients that might be listed will be very vague. Notice that no synthetic fertilizers are listed, even if they are there in quantity. Anyone can sell any dirt as topsoil, and people often do as a means to avoid disposal fees for dirt. Get top soil from people removing their raised beds, those who have graded the top few inches of an area, people taking out lawns, etc. or from your own backyard. If there are unused areas of your yard that support a dense mat of weeds, at least during wetter, warmer months, then that is true top soil. Yes there will be weeds, but a good mulch will take care of most of that problem. My advice to any gardener is to start with good top soil, nurture that soil by continually adding organic material, worm castings and compost tea, and use a good mulch. These items are 80-90% of the battle for the vast majority of plants.

David - this is written in a conversational tone, even though I disagree with you on a couple of points. First, the reason I don't reuse my potting soil, and I start with a soil that has as its primary fraction, large particles of pine bark, which takes 4-5 times longer than peat to break down, is that I have found it VERY advantageous to keep my focus on aeration. There are actually ways to quantify a good soil and compare it to a lesser soil by examining it's total porosity and air porosity at container capacity. Container capacity is the soils state of water retention after it has been completely saturated and has just stopped draining. You cannot achieve a level of either total porosity OR air porosity at container capacity using broken down particles of peat/compost/coir as the primary fraction of your soil, even with a considerable volume of perlite added. If you are left with nothing but perlite, which doesn't seem like something that would occur as a common scenario in normal cases of soil aging, then we really aren't talking about reusing an old soil; rather, we'd be talking about reusing the old perlite fraction, which is something quite different. So, if you are reusing the old soil as a significant fraction of the current soil, its very likely you're putting yourself at a distinct disadvantage because of the inherent reduction in aeration and probable excess water retention. I'm not pointing out these facts to disparage how you grow, only so we can understand that SAYING a soil drains well (or is well-aerated) doesn't mean it actually does (or is). We KNOW that fine particles hold more water than coarse particles (of the same material) and vine organic particles tend to compact, further reducing aeration and increasing water retention. IF you were to use inexpensive pine bark as the primary fraction of your soil, and add enough of your used soil to arrive at a favorable state of water retention, you would end up with a soil that DOES have favorable total porosity and air porosity at container capacity. If the soil is entirely broken down as you suggest it is, you STILL need to buy something to replace the lost volume, unless you're using compost ..... and then you end up right back where you started - so why not buy inexpensive pine bark instead of another finer ingredient? Something I wrote on another thread about rooting in water: Though roots form readily and often seemingly more quickly on many plants propagated in water, the roots produced are quite different from those produced in a soil-like or highly aerated medium (perlite - screened Turface - calcined DE - seed starting mix, e.g.). Physiologically, you will find these roots to be much more brittle than normal roots due to a much higher percentage of aerenchyma (a tissue with a greater percentage of intercellular air spaces than normal parenchyma). Aerenchyma tissue is filled with airy compartments. It usually forms in already rooted plants as a result of highly selective cell death and dissolution in the root cortex in response to hypoxic conditions in the rhizosphere (root zone). There are 2 types of aerenchymous tissue. One type is formed by cell differentiation and subsequent collapse, and the other type is formed by cell separation without collapse ( as in water-rooted plants). In both cases, the long continuous air spaces allow diffusion of oxygen (and probably ethylene) from shoots to roots that would normally be unavailable to plants with roots growing in hypoxic media. In fresh cuttings placed in water, aerenchymous tissue forms due to the same hypoxic conditions w/o cell death & dissolution. Note too, that under hypoxic (airless - low O2 levels) conditions, ethylene is necessary for aerenchyma to form. This parallels the fact that low oxygen concentrations, as found in water rooting, generally stimulate trees (I'm a tree guy) and other plants to produce ethylene. For a long while it was believed that high levels of ethylene stimulate adventitious root formation, but lots of recent research proves the reverse to be true. Under hypoxic conditions, like submergence in water, ethylene actually slows down adventitious root formation and elongation. If you wish to eventually plant your rooted cuttings in soil, it is probably best not to root them in water because of the frequent difficulty in transplanting them to soil. The brittle "water-formed" roots often break during transplant & those that don't break are very poor at water absorption and often die. The effect is equivalent to beginning the cutting process over again with a cutting in which vitality has likely been reduced. If you do a side by side comparison of cuttings rooted in water & cuttings rooted in soil, the cuttings in soil will always (for an extremely high percentage of plants) have a leg up in development on those moved from water to a soil medium for the reasons outlined above. Al

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.