Hilary, our fearless leader at the student farm, has decided that the soil that is the next hoop house block is crap.. She has decided to go big or go home, block Hoop House A will be double dug. I thought i would explain what double digging is based on my experience on a farm in Washington State..
Double digging is a bed preparation method that provides permanent fertility. This double digging practice is part of the Grow Biointensive method of farming, a combination of the French intensive method and Biodynamics. Introduced by Alan Chadwick in the 1960s at the University of Santa Cruz as the biodynamic/French intensive method; this method of farming focuses on soil fertility and utilizing space appropriately. Chadwick studied under Steiner, and the French gardeners; he understood that soil fertility was extremely important and used the double digging method to integrate compost into the soil and create 24 inches of topsoil in just 5-10 years which is quick compared to nature which takes about 2,000 years to accomplish the same thing. The French intensive system of gardening was developed in the 1700s, outside of Paris, where crops were grown on 18 inches of horse manure and planted so closely together that their leaves would barely touch at maturity and weeds were shaded out. The French intensive system used some of the first known season extension methods, placing glass jars over crops in the winter. Biodynamic methods were introduced in the 1920s by Steiner which included soil fertility management via compost preparations. John Jeavons and the Ecology in Action team simplified and altered the Chadwick method to become the Biointensive method which can be fully understood from the book: How to Grow More Vegetables Than You Ever Thought Possible on Less Land Than You Can Imagine by John Jeavons.
Double digging is the one time, extreme, method of preparing your soil’s fertility forever, with only small additional seasonal tasks. Once you have your beds planned out, soak hard clayey soils for two hours, and let dry for two days. If your soil is wet while you try to dig, it will be very heavy and tiring. Loosen the first 12 inches of soil with a spading fork and integrate soil texture amendments; add sand to clayey soils or add clay to sandy soils, mix well. When the soil is ready to be double dug, remove the first 24 inches of soil from the first trench. The trench should be about 20 inches long, and left in a wheelbarrow to be used at the end of the process. Loosen the soil another 12 inches and add two 5 gallon buckets of compost; we used moist cow manure from winter housing. Mix the compost with the loosened soil. Start the next trench. We use posts to mark our distances (every 20 inches). Add the topsoil from the second trench into the first trench. Continue this process of digging a 20” trench at a time and adding the top soil to the previous trench. Once the bed is completed, rake out the bed into a rounded turtle-shell shape. This turtle-shell shape was designed to recreate the fertility of a land slide which allows air, moisture, warmth, nutrients, and roots to penetrate the soil. Once the bed is raked out, add a layer of compost and cover with straw. This bed will settle over time and the mound will shrink in size. To counteract the settling, every season the bed should be aerated using the Ubar, a large pitch-fork looking device that goes 24 inches into the soil then pulled through the soil to aerate (see book for picture). You will find double digging is extremely labor intensive but not only do you receive permanent fertility in your bed but you gain a stronger back and an passionate appreciation for the soil.
Sources: Jevons, John. How To Grow More Vegetables…, 7th edition 2006
Moon update: Waning crescent tonight.
Next Full Moon: April 15th <– Shakori Hills Moon Bathing.