Potting Mix Step Two: Fortifying the Mix

The new year has arrived and with it the beginning of the need for new potting mix.  I’ll be starting my onion seeds indoors in the next few days.  And I’ll need fresh potting mix to do it.

Step One of making potting mix consisted of removing my four-year old Slow compost and sifting it into the wheelbarrow to remove stones, oversized objects, and woody bits that hadn’t broken down, then filling my blue barrels with it.  

Step Two is to fortify the mix to make it ready for seed starting, transplant growing, flower bulb planting into portable pots, and later for filling containers of bedding plants --- flowers to set up on the driveway, deck and elsewhere.

Several years ago my son TOG (The Organic Grower) gave me the recipe for fortifying the new mix.  I think he got if from either Eliot Coleman or Steve Solomon.  The recipe uses organic accepted ingredients or vegetative amendments from the local feed store.  It includes a source of:

1)    Lime – to smooth out the mix’s PH.

2)    Phosphorus – either Bone Meal or Rock Phosphate.

3)    Nitrogen – I use Alfalfa Meal and Soya Meal, both bought from Otter Co-op as animal feed supplements.  They come in 20 kg (44 lb) sacks. 

These are the same ingredients that I use as soil amendments in my vegetable garden.  

The Alfalfa is rated at 16% crude protein and is dustier and finer milled so I tend to believe it acts faster but lasts shorter.  The Soya meal at 46.5% crude protein is milled coarser but it is ‘hotter’ and holds more kick longer. At least that’s my theory.

TOG’s older recipe is for fortifying one five-gallon pail of potting mix.

1)    Lime:  1/6^th cup.

2    Bone Meal:  1/6^th cup.

3)    2/3^rd cup of mixed half Alfalfa and half Soya meals.

     

Left to right: Soya Meal, Alfalfa Meal, Rock Phosphate, Lime.

Instead of borrowing measuring cups from my Lovely Wife’s Kitchen, I opted on making the proper sized measuring cups from old, cut down yogurt containers. 

The five gallon pail of potting soil is poured into the wheelbarrow and the one cup of amendments are sprinkled over that.  Then using a hoe, I mix it all together, chopping, scraping, and moving it from one end of the wheelbarrow to the other.  Three times.  The mix then goes into my ‘Fortified’ Barrel and is the source for all my potting mix needs.  

At least that’s how I used to do it (the hoe mixing part).  With my old shoulder getting older by the day, a few years ago I bought a small electric cement mixer to do my mixing for me (as well as some concrete work).  A few days ago, my Lovely Wife and I got an assembly line going and we filled the Fortified Barrel in about an hour.

TOG goes through a lot of potting mix at his vegetable farm and he doesn’t use a four-year old compost as a base.  He uses peat as a base instead.  His growing mix base consists of:

1)     5 parts peat – sifted to remove any sticks.

2)     3.5 parts compost – his batch is usually 1.5 years old.

3)     1 part Perlite – medium sized.

Coleman also recommends throwing in a bit garden soil but with our compost we feel we are adding adequate ‘life’ onto the mix.  Plus I’m loathe to add anything that might add clay into the mix for clay turns to almost concrete in a pot.

TOG’s fortifying recipe has changed over the years and his needs are a bit different than mine.  Many of his transplants are in the ground within 2 to 4 weeks.  He uses a paper pot system -- one inch square and two inches deep, with a unique planting tool (it looks like a kid's larger wheeled scooter) that releases the small pots, in an accordion kind of way that draws them out in a line and plants them into the bed.

His fortifying recipe for those smaller pots is ‘hotter’ and ‘quicker’. 

1)    4 parts blood meal (or 3 parts blood meal and 1 part alfalfa meal)

2)    1 part kelp meal – an excellent source of trace elements.

3)    1 part lime.

4)    1 part bone meal or rock phosphate.

He mixes that up and adds one cup of it to each 5 gallon pail of peat/compost/perlite base mix.  On a tight budget one could possibly replace peat with old leaf mold if you knew where someone had been dumping leaves for years.

In one season we tend to use at least one 50 gallon barrel of potting mix for all our vegetable and flower seed starting and transplanting needs.  If more is needed, I’ll mix up / fortify enough to start the new strawberry transplants in the mid-summer and a bit more for some containers of pansies for the fall and winter.

The mix in the flower containers that are finished in the fall are recycled back into the first blue barrel to be fortified again the next spring.  After two seasons the used mix is tossed into the garden and is an excellent soil conditioner.  Any four-year old slow compost from my old compost box that doesn’t fit into my blue barrels under the deck goes into my vegetable beds as well.  

My supply of raw potting mix lasts about four years and that’s when my next Slow Compost box is ready to be emptied again. 

Happy Gardening.