Ran out of $....Making my own mix

[Walt B.]

First time dabbling with self watering containers. I built two sub-irrigated raised planter boxes..... and built them too large apparently. I didn't realize how much the growing media was going to cost. I'm going to need 28 cubic feet of mix for the first box and 23 cubic feet for the second. I was planning on putting tomatoes in the large one and other vegatables in the smaller one. I was planning on using Raybo's formula (3-2-1) for both boxes. I can't afford to use Promix as suggested.... its just too expensive for the amount I need. I picked up Premier peat moss from Lowe's....... fir bark fines (smaller than 3/8".....couldn't find pine bark fines).....and perlite to make my own mix. My questions are:

1) how much dolomite lime should I add?
2) will I be alright with the fir bark fines instead of pine? They're both softwoods....
3) I need some fertilizer recommendations for boxes this size
4) Do I need to add anything else ..... wetting agents, etc.
5) can I use Raybo's formula for most vegetables......or just tomatoes?

Thanks for your expertise.

[fonseca]

I can answer #1. My soilless mix is 1/3 peat. I add dolomite lime at 1 tablespoon per gallon, or 1/2 cup per cubic foot of the total volume of soilless mix.

Many commercial peat-based mixes are as much as 70% peat. For those I use 2 tablespoons DL per gallon, or 1 cup per cubic foot. 2 TBS/gal is a safe amount and commonly used to amend commercial peat mixes.

I can't help you on the bark and perlite question. I have eliminated both from my sub-irrigated containers. But lots of members here use pine bark fines with good results.

[coldframer]

oooh! 1/3 peat and what else? I'm always looking for a new idea...

[simmran1]

Basic Container Mix

1 bucket (2-½ gallons) peat moss
1 bucket(2-½ gallons) vermiculite or perlite
A half bucket (1-¼ gallons) screened compost or composted cow manure
2 cups fine sand
2 cups pelleted time-release fertilizer
½ cup lime (to counter the acid of peat and keep the pH level near neutral)
Mix thoroughly. Makes enough to fill two 14-inch tubs or five 12-inch hanging baskets. Double or triple recipe for bigger containers.
How Much Mix Do You Need

Potting mix is sold by volume (measured in quarts), and most pots are measured by their diameter. To translate quarts of mix into various pot sizes, use this quick reference.
Container Size & Amount Needed

Pots & Tubs
8-inch 3 quarts
10-inch 6 quarts
12-inch 8 quarts
14-inch 12 quarts
16-inch 20 quarts
20-inch 24 quarts
24-inch 28 quarts
30-inch 72 quarts
36-inch 96 quarts
Hanging Baskets
12-inch 6 quarts
16-inch 10 quarts
Window Boxes
24-inches by 6-inches 12 quarts
36-inches by 6-inches 20 quarts

[BajaMitch]

Fact #1 - When you mix a gallon of peat and a gallon of perlite, put it in the pot and then wet it, you will get about 1.6 gallons of damp mix. The mix will compact by at least 21% of dry volume after irrigating with water.

Fact #2 - Since you are sub-irrigating by way of your self-irrigating containers, you need the mix to be capable of wicking up the water. That requires a suitable proportion of peat in the potting mix. A potting mix that contains at least 60% peat moss is good.

I would not recommend using sand in your potting mix as it does not wick and does not provide the electrical properties that your grow mix needs for the fertilizers to adhere to in order to be available for uptake by the plant roots. Sand promotes water drainage, you self-watering containers need the opposite, that is, wicking "up" of water.

Be careful of the quantity of compost as that doesn't wick that well either.

If you want to control cost (one of my main goals in life), Home Depot or Lowe's has 3 cu ft packages of Sphagnum Peat for about $12.47 plus tax, that's about 22.4 gallons. For my SWCs, I use Kellogg's Premium Outdoor Potting Mix in the 1.5 cu ft package ($5.97 plus tax) in my mixes. It is about the same price per gallon as the Peat. Shop around at hydroponics stores for low costing perlite. I found a place that had 4 cu ft packages for about $14.

For further savings, don't by the pre-packed composts; they're expensive. Look around for horse stables or the like that make compost. I have a place in Orange County, CA that I pay $2.5 for 1.75 cu ft of compost. They gave me the current chemical lab analysis of it, so I know how much of each nutrient is in it to the gram; much better info than anything written on any pre-packaged bag of compost.

This year I am making my own potting mix for 16 buckets, about ten of them are self-watering. For the SWCs, the mix ratio I am using (by volume) is 6.7% compost, 1.5% fertilizers, 6.5% fertilizers, 32% potting mix, 40% peat, 20% perlite. The ratios for fertilizers and potting mix will differ for different sized containers. In the smaller containers, the ferts will be 2.8%, potting mix 30.7%.

My cost per gallon of mix (including all fertilizers and lime) for the SWCs is about $.85/gallon for the smaller containers, $.65/gall for the larger containers. For the non-SWCs, it's a little less per gallon.

Oh, BTW, I use an array of about 12 different fertilizer components that I concoct to save another 50% on fertilizers as opposed to buying just straight packaged tomato fertilizers.

Good luck.

[Ricky Shaw]

Yeah, what Mitch said. Except, zero compost for me and the ferts would be a three part water soluble with every watering.

[yardn_gardn]

Walt, for question number 2, about fir bark: I've used somewhat decomposed Dougless fir bark for potting orchids; it worked great. Then the other day, I was spreading some of the same (similar) material on my garden, and it actually had a few earth worms working their way through it. Also, our community garden uses it on their tomatoes. I'm using it this year. I'm fairly certain that it should work for your tomatoes too.

[fonseca]

I have found that compost at 1/3 the total volume of soilless mix is as much as I can get away with and still have good wicking action. Vermiculite works much better than perlite in my tests, but that would certainly depend on the mix. I love compost and feel that it has many benefits, personal preference but that's what I like to grow in. My SIPs all have red wrigglers and earthworms in them as well. My philosophy is that if I keep the worms and the microherd happy, the plants will follow.

Somewhere I have a gardening book from the 1800s with a container soil recipe for citrus trees, and the recipe is still common today: one third each animal, mineral and vegetable manure. The animal manure was "well-rotted" horse or cow dung; mineral manure was decomposed granite, as from the base of a cliff; vegetable manure was sedge peat. This was to sit for several years and then be amended with an eighth of pigeon dung IIRC.

Anyway, I follow similar ratios of one third each compost, vermiculite and peat. Instead of pigeon dung I use composted chicken manure/bedding, which is high NPK and can burn seedlings. My mix only sits for a few weeks to a month before use. I keep it moist with aerated compost tea.

[Ricky Shaw]

Just one opinion, but here is Promix's reasoning on compost in containers.

Why Compost is Not a Good Choice for Professional Growing Media.

http://www.pthorticulture.com/en/tra...growing-media/

[Gerardo]

1) how much dolomite lime should I add?
answered
2) will I be alright with the fir bark fines instead of pine? They're both softwoods....
they do fine in my garden
3) I need some fertilizer recommendations for boxes this size
17-17-17 is pretty cheap
4) Do I need to add anything else ..... wetting agents, etc.
Not really. Epsom salts at some point.
5) can I use Raybo's formula for most vegetables......or just tomatoes?
very versatile, you'll just need to feed more or less. Carrots you prob want to go as soft as possible.

Aerated compost-alfalfa teas sure do help. Best of luck!

[fonseca]

Promix is manufacturing a commercial product that gets distributed all over the US and has to be able to store for years, while still being consistent. Their customer base is comprised of professional growers that usually feed synthetic nutrients with every watering, and home enthusiasts that want to dump a mix in a few containers and feed miracle gro, or use it as a base ingredient like I do.

I'm not trying to make a commercial product, I'm trying to make the best possible environment for plant roots that contains a healthy, extremely active population of microorganisms to break down the organic nutrients and boost the plants' defenses against pests and disease. It's more work and I have to refresh my containers every year, but I also never have to worry about pH, rarely have calcium or nutrient deficiencies, and reuse my spent mix forever with no salt buildup.

I don't claim that compost yields more than an inert mix fed synthetic nutrients: I wouldn't be surprised if you could reach twice the yield that I do. My goal is to grow the best-tasting, most nutrient-dense produce possible that I can eat straight from the garden without worrying about washing.

[ricman]

I make my own container mix for my RGGS. I mix mine up in 30 gallon batches
50%-compost
50%-peat
2 cups dolomite lime
1 cup bone meal
1 cup gypsum
1 cup azomite
1 cup 10-10-10 fertilizer
3 to 4 coffee cans of perlite

I use compost in my mix because its free (always trying to save a buck) and it works well for me. If you ask 10 people what's in their mix you may get 10 different replies. I say go with what works best for you and your growing conditions.

[BajaMitch]

I see that you have both bags and buckets in your RGGS. I am sure that you have net pots at the bottom of the buckets.

Ricman, how do you water your bags? From the top? Or, is there a trough of some kind filled with water underneath the bags? If so, how does the water in the trough reach the bags? Are the bottom of the bags 'pushed' into the water in the trough?

[luigiwu]

Ricman, LOVE it!

BajaMitch, Larry has a very long video but if you are only asking about what to do with the bag, go to the 10 min mark there abouts. Bags work the same as buckets over the gutter trough like Ric's pic.
https://www.youtube.com/watch?v=CclTbusP7Ms

[ricman]

BajaMitch-Yes the bags also have net cups in the bottom of them and the sit on top the rain gutters that are filled with water. Like Luigiwu mentioned there are many great videos on YouTube concerning Larry Hall's RGGS, should you be interested. Its a great
way to garden IMO.
Luigiwu-Thanks for the kudos. How's your RGGS coming this year? I just came in from the garden. I was trying to find room for three more wayward tomato plants.

Rick