Here is the thing. I do container gardening, so I make my own soil mixture. I don't do gardening using a traditional row format, as I don't have the space to do so, and even if I did, the soil where I live is nutrient-poor and not suitable for gardening.

How do I get a soil test for container gardening. I realize I could take a sample of it and send it an agricutural extension office, but don't they normally test soil in large quantities and from the ground (not soil mixtures that somebody would mix up themselves for container gardening).

Could I just use one of those soil test kits found at a local hardware store? Would this be sufficient or should I go the route of sending a soil sample to a county extension office?

If I choose to send the soil sample to a county extension office, how long will it take for me to get the results of the test after I mail it?

For reference, here are the mixtures I make for container gardening. I use both size quantities, it just depends what size container I'm using which one I use.

However I can't make it now, as it's too early to grow stuff where I live ( I won't be able to start sowing cool weather crops until late March/early April)

As a result, how can I send out a sample of the soil mixture now? I'd like to get this done now since I can't do anything else, but what am I supposed to do if it's too early to mix up a batch of the soil? As a result, I can't send a sample.

A NOTE: Please don't tell me to post this in container gardening forum. I realize this pertains to container gardening; however this is more about the contents of my container gardenining soil mixture, then any specific questions about container gardening itself. That's why I posted this here.

Big batch:
2-3 cu ft pine bark fines
5 gallons peat
5 gallons perlite
2 cups dolomitic (garden) lime (or gypsum in some cases)
2 cups CRF (if preferred)
1/2 cup micro-nutrient powder (or other source of the minors - provided in some fertilizers)

Small batch:
3 gallons pine bark
1/2 gallon peat
1/2 gallon perlite
4 tbsp lime (or gypsum in some cases)
1/4 cup CRF (if preferred)
micro-nutrient powder (or other source of the minors)

Testing of container soil is not necessary. And that's because container soil generally contains no soil! It is typically comprised of rather durable ingredients that have little to no nutrient value, so testing - other than perhaps pH - is of no benefit. While there may be some small nutrient value, container gardening holds the concept that ALL nutrients must be supplied from outside sources, not from the ingredients themselves. And rather repeatedly at that, as frequent watering leaches nutrients rapidly from containers.

The homemade mixes you proposed in your previous post(s) are not going to get you the results you want. Organic fertilizers - like the kelp or fish meals, cottonseed meal, even the blood and bone meal - are just very inefficient nutrient sources for container gardening. The organisms required for these to be properly converted into usable plant nutrients are simply not present or not present in sufficient populations to effectively convert these insoluble nutrient sources into the soluble forms the plants can access. And even when they are present, nutrient availability/delivery is very erratic.

You will be much better off purchasing a premade all-purpose liquid or water soluble non-organic (synthetic) fertilizer (and one that includes necessary trace elements) to fertilize your containers. Then there is no need to guess if each plant is getting what it needs for optimum growth and production - it's all there. An all-purpose type is fine for any type of planting, including veggies, but you can sometimes find more specific formulations if you desire. Water soluble synthetics make it far easier to determine the exact amount of nutrients required by/provided to the containers and you can be assured the plants are getting what they need when they need it. Most container gardeners follow this method, many incorporating a slow release fertilizer as part of their mix or when they pot up a container, then following that up with frequent periodic additions of a soluble fert. Organics - as great as they are for inground gardening - really just don't cut the mustard in this situation :-)

btw, your follow up about not posting this question in the Container Gardening forum is just a little shortsighted as well. As I hope you realize, container gardening has vastly different requirements and conditions than that of inground or even raised bed gardening and ANY question you have regarding any aspect of container gardening - soils, soil ingredients, nutrients and fertilizers - can all be answered just as thoroughly (maybe even more so) on that forum than they can be in a more generalized forum. There are very knowledgeable participants there with years of experience that can answer any question you can possibly think of that has to do with growing any plant in a container.

However it's completely useless for other types of vegetables.

I know from research that fruiting plants need a fertilizer high in potassium and phosphorus and root vegetables also need a fertilizer high in potassium and phosphorus as well.

If you can recommend a specific fertilizer that is high
in potassium and phosphorus I'll be happy to use it.

However as stated before a high nitrogen fertilizer is going to be completely useless for root vegetables and stuff that is grown for the fruit (eggplants, tomatoes, bell peppers, any type of melon, any type of squash, any kind of bean, carrots, beets, red radishes, white asian radishes, carrots, turnips)

Folks have been successfully growing container veggies for years using only an all-purpose (all 3 numbers the same) type of liquid or water soluble fertilizer. They work, and if they supply all necessary trace elements as well and are applied as needed, they work pretty darn well! I personally use an organic 3-3-3 liquid on all my container plantings and have had no issues with production or overall health and vigor.

Alternatively, many container gardening folks use the all-purpose ferts in an extended release form when they pot up their containers and then follow-up later with a weekly or biweekly liquid bloom and fruit fert formulation (often called "bud and bloom boosters"). Look for something with a 1-3-3 or 1-3-2 ratio to offer higher P & K levels.

Dyna-Gro is a very popular liquid fertilizer for container gardening (NPK 7-9-5). You can use this throughout the season without worry. If you feel the need, you can switch to their Liquid Bloom formulation (3-12-6) to encourage flower and fruit production.

But there are many other ferts you can use - any water soluble fert (MiracleGro, Peters, fish fertilizer, seaweed/kelp emulsion, etc.) or hydroponic nutrient mix can do the job just as well.

FWIW, none of your questions are unique or even uncommon - ALL these points have been addressed very thoroughly on the Container Gardening forum and questions about fertilizing containers to maximize production come up frequently. You might want to review the attached link that summarizes much of what you need to know about providing nutrients to container-grown plants. It is very helpful!!