The double-dig is the principal way one prepares a GROW BIOINTENSIVE bed until good structure is established. Afterwards, one will depend on surface cultivating the top 2 to 4 inches. Another way to keep cultivating the top 2 to 4 inches. Another way to keep soil loose between double-digging is to single-dig (loosening the top 12 inches with the spading fork).
We recommend doing so between crops in the same growing year. Spread a layer of compost over the entire area to be dug. After marking the bed, place the digging board on the bed, leaving approximately 24 inches from the end of the bed for the +rest trench. Remove 7 +vet-gallon buckets of soil from the upper level of the +rst trench (assuming a 5-foot-wide growing bed; see illustration on this page). Be sure to dig trenches across the width of the bed.
This will give you 3 buckets of soil to make compost (these will eventually be returned to the growing beds in the form of cured compost), 1 bucket of soil to make flat soil to grow seedlings, and the remaining 3 buckets are returned to the bed after it is dug Now, standing in the trench or on the digging board above the trench, dig down another 12 inches (or as deep as possible) with a spading fork, a few inches at a time if the soil is heavy or tight.
Leave the fork as deep as it has penetrated, and loosen the subsoil by pushing the fork handle down and levering the tines through the soil. If the soil is not loose enough for this process, lift the chunk of soil out of the trench on the fork tines. Then throw it slightly and gently upward, and allow it to fall back on the tines so it will break apart some.
If this does not work, use the points of the fork tines to break the soil apart. Work from one end of the trench to the other in this manner. Next, move back the digging board (approximately the 12-inch width of the next trench). Dig another trench behind the +rest one, moving each spadesful of the top 12 inches of soil forward into the +rest trench.
When digging, make as few motions and use as little muscle as possible in this process. This will conserve your energy and involve less work. In fact, as you dig the soil, you will discover you can use an Aikido-like economy of motion and energy in which you are virtually just shifting your balance and weight rather than digging.
Sometimes you will have to work over a trench a second or third time to remove all the soil and obtain the proper trench size. Repeat the subsoil loosening process in the second trench.