notes on preparing and amending raised bed vegetable garden soil

As I get ready to plant the newly-built raised bed at my new-to-me house in Edmonton, I keep referring back to notes I posted on my old Calgary Garden Coach blog.  So I’m copying them over here.  And here is what my old veggie garden looked like in its first year:

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Excerpts from Calgary Garden Coach, April 2011:

According to Mel Bartholomew, author of Square Foot Gardening, a good vegetable garden soil should be made up of at least 25% (up to 50%) of soil amendments such as compost or leaf mold.  Another good rule of thumb is to add 10 – 20% by volume of coarse vermiculite to a new vegetable garden for good moisture retention – vermiculite is like a sponge.

But once you’ve prepared your initial soil, how do you keep amending it each year to maximize production?  Mel Bartholomew has lots of recommendations.  He says (and I agree), “trying to grow crops in any kind of soil without constantly adding organic matter is sheer folloy and a waste of time, no matter how much fertilizer you add to it.  On the other hand, to garden in soil that is rich in organic matter but contains no added fertilizer is not only possible but also very practical.”  He recommends:

  • add a trowelful of compost or other organic soil builder after you harvest each plant in your garden – this will probably mean you are amending at least 2x per year, maybe even 3 or 4
  • supplemental fertilizers to use during the growing season need only be of 2 types: a high nitrogen fertilizer for leaf crops (eg. lettuce, spinach, chard) and a high phosphorous and potassium fertilizer for root and fruit-bearing crops;
  • you can add dry fertilizers when the soil is prepared for planting, plus once a month as crops are growing, in the form of a pre-packaged organic mix, or make your own, see recipes below
  • heavy feeding crops (eg. brassicas) will also benefit from supplemental watering with compost tea, fish emulsion, or seaweed/kelp solutions

Basic, all-purpose fertilizer recipe

  • 1 part bloodmeal
  • 2 parts bonemeal
  • 3 parts greensand
  • 4 parts composted leaf mold
  • approximate NPK value: 2.6 / 4.9 / 1.8

High-nitrogen fertilizer recipe

  • 3 parts bloodmeal
  • 2 parts bonemeal
  • 3 parts greensand
  • 4 parts leafmold
  • approximate NPK value: 4.6 / 4.3 / 1.6

I haven’t been nearly as diligent as I should have been in the past and still got decent results, but this year I am vowing to follow his recommendations to try to maximize my harvest. What do you do in your vegetable garden?  Please share in the comments section below.

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One thought on “notes on preparing and amending raised bed vegetable garden soil

  1. I like the idea of adding a scoop of compost as each plant is harvested :o) We (here in Edmonton as well) have a compost bin for our veggie scraps & will probably add about 2-3″ of the overwintered compost to the raised bed before planting this spring

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