It depends a lot on the medium being used, but primarily it relates to the uniqueness of container growing culture compared to growing plants in the ground. Because of the need for very fast and long term good drainage, most container mixes are soil-less mixes, containing little if any real "dirt" or soil, therefore providing a minimal habitat for any soil organisms. In some cases, this soil-less mix is even pasturized or sterilized to eliminate pathogens and so eliminates the good guys as well. Non-pasturized or sterilized potting mixes may contain some beneficial soil organisms but not to the same high degree they exist naturally in the soil. And because the container is essentially a closed environment with little opportunity to encourage or develop larger populations of these organisms, they do not flourish.

Organic fertilizers or those derived from plant or animal extracts or byproducts are almost always insoluble and cannot be immediately accessed by plant roots. They require the activities of the soil organisms to break them down into plant accessible solutions and if the soil organisms are not present or not present in sufficiently high populations and diversity, this just doesn't happen and the organic ferts remain essentially inert and wasted.

There are various ways to get around this. One is to formulate your own potting soil mix that includes more of the organic matter that the microbes, fungi and bacteria reside in naturally and need to thrive. But you run a risk of creating drainage issues if you use too much of this - a bit of a catch-22. You can also purchase commercially prepared potting mixes that are innoculated with beneficial organisms, but they tend to not be widely available and are relatively expensive. Or you can use a soluble organic fertilizer that bypasses the need for soil microbes to break down. Fish emulsion, kelp emulsion and similar products are examples of this.

Does this answer your question?

Gardengal, thank you so much."soluble organic fertilizer" are the words I think I needed to see. I use these as a foliar feed and drench in my containers and on my roses and could not believe that they weren't working because I can see the difference in my plants after I use them. And thank you for using language that didn't overwhelm me with your intelligence. Anita

Try the Organic Gardening forum - the Botany forum is more for things like plant classification and so on.

Resin

Here is a link that might be useful: Organic Gardening

The description of the botany forum is "This forum is meant for the discussion of botany and all aspects of the scientific study of plants." Undesrstanding how nutrients is one of most important aspects of botany that is over looked by the heavily affected. The OP's question is valid for this forum.

One add on, souble fertilizers such as fish emulsion still wil need microbial action to make the nutrients available to plants.

Thanks guys, I came over to lurk after seeing you mentioned on another forum. I had to change to container gardening because of health problems and i too was wondering about liquid organic fertilizer. Guess i'll have to stick with Miracle Grow. Thanks again.

I just stumbled on this thread, but I think that the OP's description of the thread on the Container Forum "... organic fertilizers not working in potting soil, even with beneficial fungi added." is rather inaccurate. What was put forth in the thread is that chemical soluble fertilizers are immediately available for plant uptake, while organic fertilizer matter requires the activity of the microbial population for nutrient availability/delivery; and that the microorganism population in container culture is subject to the negative effects of wide variety of cultural conditions, which tends to make microorganism populations occur in boom/bust cycles and nutrient availability/delivery erratic. I think the strong possibility of carryover of some fertilizers during periods of low populations was also discussed.

The advantages/disadvantages of chemical and organic nutrition supplementation programs were looked at primarily from results and ease of implementation oriented perspectives, which pretty much left out the argument between the rigidly organic gardeners and those who don't have strong feelings one way or the other.

Al

Thanks for the post, Anita. I really needed the info here.

~Angela

"soluble organic fertilizer"

Is this the reason why, when I had two 10 gallon containers growing all summer of "yellow sweet rasberries", the ones that got fed a constant feed of "fish emulsion" grew twice bigger, and big fat and juicier, than the one that got fed just "inorganic fertilzers". Both tainers contained a soilless mix...

Does feeding "fish emulsion" from "Neptunes Harvest" help houseplants too, or make a difference, as a supplement with my regular chemical fertilizers that I use?

I would love to know, before I go and purchase more of the emulsion. It is 35$ a gallon. Would I be wasting my money using it in a soilless mix for my houseplants?

Thankyou

Anyone?

Mike, after reading the info from this thread and studying what Tapla writes, I don't use organic in any container. Even my ferns are thriving with Miracle Grow and Monty's Joy Juice. The garden still gets both fish and kelp from Nept. Harv., there's plenty of bacteria out there. I don't see a difference in any plants here unless they just aren't fertilized. (but I'm not the sharpest tool in the potting shed) Anita

Thanks gree-knees!
Good comment
I also had a good explanation from Al'
Have a great weekend!!:-)