Using compost for container vegetable garden

fadfodehMarch 27, 2014

I am planning to start a container garden on my balcony this year. I will use bags of 40 liters each for each plant (tomato, green pepper, eggplant).
I would like to use compost as the soil in the container, but I am not sure which compost should I use. What are the specs/ingredients (NPK) that I should obtain for this purpose?
P.S. I am not planning to use any amendments during the growing time.

Thank you for your help

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Ohiofem(6a Ohio)

Fadfodeh: Compost does not work as a major part of the mix in containers. It gets compacted and interferes with drainage. Many of us follow the advice given in the discussion I will link to below, which explains how growing in a container is very different from growing in the ground. There is a recipe for making a soil mix called 5-1-1 that works very well. From your reference to liters, I assume you live outside the United States. It would help if you tell us where you live and what your climate is like.

Here is a link that might be useful: Container Soils - Water Movement and Retention

    Bookmark   March 27, 2014 at 9:41AM
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Thank you for your feedback.
I live in a Mediterranean country, hardiness zone 7 or 8.
In summer, temperature goes up to 110 max, and humidity is about 70'% on average.
The problem with your 5-1-1 formula is that most of the materials do not exist in our market, while maybe other similar materials exist naturally.
The purpose of this plan is part of an initiative to promote organic gardening in the society, where a startup kit is provided to them which includes: some basic containers, seedlings, and growing media. While on the other hand teaching them how to prepare their own compost for future gardening activities. We need to make this initiative as simple as possible for them to encourage them to work further in this direction.

Thank you again for your help and best regards

    Bookmark   March 28, 2014 at 7:30AM
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Ohiofem(6a Ohio)

I'm afraid your situation is so different from mine and that of most others in this forum, that we might not be able to help you. Helping people do self sustaining organic container gardening in your community sounds very worthwhile. You might want to ask people in the Soil, Compost and mulch forum, who are experts on making compost. Another gardenweb member named Saood who was growing in containers in Saudi Arabia was a regular here last year. You could search on his name to see some of the answers he got. I think he goes mostly to the Arizona gardening forum now since he figured out that the climate was similar to his.

Here is a link that might be useful: Soil, Compost and Mulch Forum

    Bookmark   March 29, 2014 at 1:46PM
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drew51 SE MI Z5b/6a

In containers best not to use more than 25% compost. Unlike most in this forum i think compost rocks in containers. It's just a matter of what you mix it with. Growth and fruit production is too good not to use it.

    Bookmark   March 30, 2014 at 9:45AM
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Thank you guys for your great help. I have re-posted the message in the Soil, Compost and Mulch forum

All the best

    Bookmark   March 30, 2014 at 3:40PM
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seysonn(8a WA/HZ 1)

I have seen some university ext. recommending it too.

below is University of Flodia Article.

Here is a link that might be useful: compost as container soil

    Bookmark   April 2, 2014 at 1:18AM
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hairmetal4ever(Z7 MD)

Compost is great to put in your outdoor garden.

Not in a container.

    Bookmark   April 2, 2014 at 11:41AM
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seysonn(8a WA/HZ 1)

Compost is great to put in your outdoor garden.

Not in a container.
Certainly your personal opinion and choice. I just linked University of Florida article(in my previous post) recommending its use in containers.

    Bookmark   April 2, 2014 at 12:07PM
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greenman28 NorCal 7b/8a

It's an opinion shared by many who've grown extensively in containers.

If we're talking big containers (which are basically mini-raised beds), then the drainage won't be as negatively affected. If we're talking the standard small containers that folks use, compost is an ingredient best limited to about 15% of a mix (the same fraction that I would substitute for peat/potting mix when making a 5-1-1).

All gardening is local, of course, and in warmer climates there is greater leeway in using heavy, moisture-retentive ingredients.


    Bookmark   April 2, 2014 at 12:20PM
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Ohiofem(6a Ohio)

The term compost means something different in the United States than it does in Britain, and the OP may have been using it in a different way than is commonly understood on this forum. The British and Europeans often use the noun "compost" to mean potting mix. A common potting mix in Britain is called John Innes compost. The NPK is supplied by a combination of organic amendments. Here's a description.

John Innes Composts are a blend of carefully selected loam or topsoil, sphagnum moss peat, coarse sand or grit and fertilisers. The loam is screened and sterilised and then thoroughly mixed with the other ingredients in proportions designed to achieve the optimum air and water-holding capacity and nutrient content for different types and sizes of plants.

Sorry to say that when I started out growing container plants back in the day, I got all my advice from Thalassa Cruso, who was the Julia Child of gardeners in a popular public television series and published several books on the subject. Everyone made their own mixes in her day.

Here is a link that might be useful: John Innes Compost recipes

    Bookmark   April 2, 2014 at 12:25PM
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