The reasons are: Too much/too little moisture - the conditions change rapidly, unfavorable pH - also changes rapidly, extreme temperature swings - changes rapidly, soil composition/compaction/aeration - compost-based soils can usually be counted on to compact badly, making anaerobic conditions ......... any one or combinations of several factors affect microbial populations in containers, and because they are tied together with nutrition organic soil supplements - nutrition as well. Since bio-populations rise and fall dramatically in containers, it follows that nutrition availability follows the activity levels and population numbers of the critters. Add to that you often have no idea of what you're supplying (% of nutrients) and when they will eventually become available, you can easily see how a chemical nutrition program for containers could be easier, less worrisome, and more reliable than depending on soil amendments to deliver the goods. That someone indicates his plants grew better in compost than commercial potting soil is no clarion call to hurry to a water-retentive medium as a solution to container culture problems. I grow in a bark/peat/perlite mix and it has been proven by many to be extremely productive, in large part because of its structural durability. The FIRST thing any container gardener should consider when it comes to soil is it's (structural) durability. The question should be asked, "Will it remain well-aerated for the intended life of the planting?" The bark based soils garner a resounding 'YES' while the compost-based soils get a weak "probably not". If compost is in large enough pieces that it is appropriate as the basis for a container soil. it's not finished and will quickly break down and collapse, bringing N immobilization along the way. If it IS finished, particulate size is too small for it to be the basis for a container soil. The chemistry and physics of container culture are often, if not usually, quite different than growing in the earth, and we often create more problems than we solve when we try to bring the garden to our containers. Al

There are probably close to a hundred recipes on line for potting soil mixes acceptable to an organic gardener but I have had good success with my compost for many years, even though there are amny that tell me it will not work and my plants will die although they have produced a bountiful harvest growing in that medium. This link may be of some help. Here is a link that might be useful: Organic Potting soil

Your organic blend NPK %s are about 2.8:0.7:1.7, which ends up being a pretty favorable RATIO of NPK. Al

I use fish emulsion for all my roses, both in the ground and in pots. Started doing this last year after a recommendation from one of my favorite rose nurseries, Greenmantle. I tried 3 different brands. The one I liked best is Gro-Tone made by Espoma. Gro-Tone is a nice balanced 2-2-2. It also smells better than fish emulsion often does. Gro-Tone certainly smells like fish but it's more like a fresh fishy aroma. Espoma added mint to make the scent less objectionable too. However it is pricey, and my local nursery doesn't intend to carry it as it didn't sell that well. I bought almost every bottle they had and stockpiled it.;) The other fish fertilizer I liked somewhat was Neptune's Harvest. The numbers on the bottle I have are 2-3-1. It also didn't smell bad though very fresh fishy(I think NH and Espoma use a cold processing method). The NH found at my local nursery is the mix which includes kelp, and I'd prefer not to give that to my roses as I don't think they need it based on soil and water conditions here--yours may be quite different. If I can't get the Gro-Tone, this is the brand I'll use, but their fish-only one which is 2-4-1. I can order direct from NH. The 3rd fish emulsion I used was made by E.B. Stone, fish emulsion with kelp, 4-1-1. It smelled ghastly, like rotten fish. Yuck, I did not enjoy applying it in the garden much less even opening the bottle. In addition, my roses did not respond as well to it as the other two. One reason may be that the water here can be very high in boron, and if the fertilizer also includes that micronutrient plants in this area may object (by showing boron toxicity). I've never seen Muskie in the stores so have never tried it. All the ones I used seemed to be in slightly different concentrations and thus the dilution rates indicated on the bottles were also different. I found this site on the web that carries Muskie: http://www.pthomeandgarden.com/product/9-muskietm-fish-fertilizer-5-1-1 It looks as if on that bottle at least there is some kind of info on the side. Perhaps it is application instructions???? Maybe they didn't put it on all the bottles which would be too bad. Melissa