09 May 2012

Double Digging

Welcome to Garden Month!  If you read Monday's post, you know that the best soil amendments increase water- and nutrient-holding capacity and improve aeration and water infiltration.  However, you can improve the aeration without adding a single amendment to your garden!  Double digging improves aeration and breaks up the soil so roots are able to grow freely.  It is inexpensive and doesn't require anything with a motor.
Start with a trench.  1 ft wide, 1 ft deep, 5 ft long.  Put the dirt in a wheelbarrow or buckets.
After you have your trench, use a pitchfork or broadfork to sift through the dirt, trying to reach another foot of depth (blue shaded area below).
Now dig up the dirt next to your original trench.  Take the next 1'x5' of dirt and put it in the first trench.  Make sure to break it all up as you go along.  The end goal here is to have a 24" depth of aerated soil.

If you have amendments that you want to add to the soil, they go in after you've dug the first foot and sifted the second foot of depth.  So the amendments end up being about a foot deep in your garden bed.
This is serious physical labor.  But it feels so good afterward.  Not only have you accomplished something tangible, you've also made your future garden VERY happy.  And this only needs to be done every few years.  It is not an annual process.
Kyle and I double dug a 5'x20' bed in about two hours (over the span of two days).  Our progress was slightly inhibited by the hedge located right next to the garden, which had roots growing out beyond the edge of the garden.
Continue this process, moving a foot of dirt at a time, until you've reached the end of your bed.  The double dug dirt should look almost like a raised bed - you've added so much space in the dirt that it is taking up more volume than before.  I know it looks like Kyle is doing all the work here, but we spent equal amounts of time behind the shovel, I promise :)
When you reach the end of the bed, go get the wheelbarrow or buckets and put all that dirt into the last 1'x5' section.  Then lightly rake everything to create a level surface so all the water doesn't run off or pool in one spot.
Look at the pretty, amended, double dug bed!  Please don't walk on it, because that will just compact the soil again and undo all your work.  And since you shouldn't walk on it, you don't want to make it any wider than 5', because then you will have a hard time reaching the center of the bed for weeding or harvesting.

Vacant soil like this is a haven for weeds, so if you don't plan on planting anything right away, keep the soil covered.  A black tarp that doesn't let any light in is one option (if you let light in, you're just making a nice, toasty greenhouse for weeds).  If you don't plan on planting anytime soon, pieces of cardboard covered with leaf mold or compost is another option - the cardboard prevents weed growth, but also decomposes to create more organic matter.

Soil amendments: check!  Double digging: check!  I think we're just about ready to get down and dirty with some seedlings!

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