Don't get me started on Whole
Back to gardening...
Growing veggies is great but your results are going to be in direct relationship to the quality of your dirt. Great dirt = healthy plants = awesome vegetables.
Step 1: What Is Great Dirt?
How does the soil in New Mexico look from a plant's point of view? Not so good. If NM dirt was being tested for the above requirements we'd have to pick...D-none of the above. Our soil tends to be either just clay or just sand and since our climate is arid enough to keep all but the scrappiest of plants from thriving we don't have much of a natural cycle of organic material building up.
Step 2: What to Do?
Double digging involves digging out all the top soil from the bed to the depth of a shovel head (about 12" ) and then go back and do a second pass to the depth of a second shovel loosening the dirt another 12" and amending it with fertilizer; traditionally horse manure cause they had a lot of it at the time.
After working the lower layer you add the topsoil back along with more manure. In the end you have a raised bed full of soft fluffy dirt with lots of organic matter.
Step 3: Adapting to the High Desert
In order to protect our plants I've learned the hard way that they need to be kept in a maximum security facility. This means my garden beds need to be lined on the sides and bottom in order to keep intruders from tunneling in and taking out half the plants in one fell swoop.
Step 4: Sifting, Sifting
This also means that there is a lot of processing to do before that dirt goes back into the bed. I sift all the dirt I took out of the bed through a 1/4" screen to remove rocks and break up the clay into smaller bits. Usually about half the dirt that I've extracted doesn't qualify as gardenworthy and ends up as backfill somewhere else.
Step 5: Bed Building
The first layer is paper or cardboard. This attracts worms. We want worms and lots of them. They're like little bulldozers and compost makers all in one. They work the soil endlessly areating it and mixing the various components together. Worm castings (poop) are also one of the richest sources of nutrients for plants.
Next I put down a 3" layer of straw or hay. A few years ago we scored about 90 bales of alfalfa for free from freecycle so that's what I use. The bales break apart easily into ~ 3" sections (leaves) and I layer the bottom with it. The straw holds a ton of moisture. It's like having a giant sponge at the bottom of the bed. Eventually it breaks down into compost providing a rich source of food for the plants down the road.
If I feel like spending the money I sprinkle a 50/50 combination of bone meal and blood meal on the straw. The nitrogen in the blood meal helps to kick off the decomposition of the straw. Lately I've switched to adding a layer of chicken poop which is high in nitrogen as well as free and plentiful around here.
After the base of paper and straw I fill the bed up with a mix of sifted soil and organic amendments. I aim for a 50/50 mix of sifted dirt that came out of the bed and organic matter. The last couple years I've been able to get trailers full of composted horse manure for free so that's the majority of what I use. I sift the manure too because there are a lot of wood chunks in it. Wood is OK once it has broken down but it ties up a lot of nitrogen from the soil as it decomposes so you want to keep it to a minimum.
About half the volume of the horse manure doesn't fit through the screen and ends up as back fill. I layer up a wheelbarrow full of soil then a wheelbarrow full of manure untill I 've filled the bed. A light sprinkling of straw or leaves in between every few layers of dirt and manure helps to add some structure to the soil and organic matter to break down in the future. Again, you don't want to add a lot because it will tie up the nitrogen in the soil.
Once the bed is filled with the soil/manure mix I stir it up with a garden fork. I do a couple passes over the whole bed to evenly distribute everything. Once mixed, I water the soil thoroughly a couple times until it is moist all the way down to the straw.
Step 6: Finishing Up
I leave a few inches of space from the top of the soil to the top of the walls. When the plants are small I lay windows on top of the bed and it acts as a cold frame holding moisture and warmth in while keeping the wind out. I've found that if I don't protect the plants during this crucial part of their development they will only grow to about half their normal size or not make it at all.
It takes a ton of work to prepare a bed this way. A 2'x 8' bed takes me 12-16 hours from start to finish but once it's completed I know I've done everything I could to give the plants what they need to thrive. After the first year all I need to do to prepare to plant is to add a 2" layer of compost on top and lightly mix it in.
Step 7: Sounds Like a Lot of Work. Is It Worth It?
If you like projects you'll find plenty more over at our site: Mike and Molly's House where we chronicle our Mighty Projects on our Mini Farm(AKA our backyard).