This is a bit of a late response, but I thought I'd chime in since my research is all about mycorrhizae and the rhizosphere. A lot of what has been said here is correct, but some of it lies in the realm of speculation. It is important to note that symbioses with mycorrhizae are not permanent and depends on environmental conditions. One of such conditions is the availability of two essential nutrients, nitrogen and phosphorous. Plants are often limited by these two nutrients, and by associating with fungi or bacteria, they are able to more efficiently gather these nutrients in the soil. To get these nutrients, plants will need to trade photosynthetic carbon for them. When these nutrients are available in excess, such as in fertilization, there is no longer a need for plants to continue the expensive trading partnership and the symbiosis thus dissolves. What this means is that choose either or. If you're going to fertilize, don't bother with mycorrhizae. If you're adding mycorrhizae, you don't need to fertilize as often. But eventually your nutrients in the pot will run out and mycorrhizae will no longer be of any help. Pathogenic fungi and bacteria are even more important to consider when growing plants. That's why we have spent so much money developing chemicals to kill them. As mentioned before, knocking down pathogen load is more important than sterilization. It is becoming more clear that a ratio between good and bad soil microbes will determine success when growing plants. This is an on-going field of research which we may see more useful results in the near future. Nhu On Sat, Feb 6, 2016 at 12:37 PM, penstemon <penstemon@q.com> wrote: > >Good information about the phosphorus, thanks! I'll add that soil > biodiversity is better with a pH of 7 or higher, as that is what it takes > for bacteria to flourish. Bacteria are at the base of the food web, eaten > by nearly every other soil-dwelling microorganism, so they are kind of > important. > > Sure. Someone told me that adding mycorrhizae to garden soil can’t hurt, > though for some plants the addition might have no effect, or it could be > the wrong kind (ecto-, arbuscular, or arbutoid), or the wrong species in > the case of a plant which is colonized by only one species, or the > mycorrhizae could be dead on arrival. > There seems to be some evidence that species dependent of ectomycorrhizae > can survive under, say, manzanitas (arbutoid), but whether or not > calochortus, which I assume are associated with arbuscular mycrorrhizae > (the most common type) would survive in a similar situation is another > story. (There’s a short paper on this subject you can download if you > Google “manzanita mycorrhizae” and then “Download Emily’s synopsis...”) > Bob Nold > Denver, Colorado, USA > _______________________________________________ > pbs mailing list > pbs@lists.ibiblio.org > http://pacificbulbsociety.org/list.php > http://pacificbulbsociety.org/pbswiki/ > _______________________________________________ pbs mailing list pbs@lists.ibiblio.org http://pacificbulbsociety.org/list.php http://pacificbulbsociety.org/pbswiki/