Plant roots need moisture, air and nutrients to grow, and a loose soil to provide room for that growth. “Double digging” is the best way to improve your soil; it improves drainage and aeration and adds organic matter. There are several good double digging methods; here’s what works for me:
Don’t dig when the soil is too wet: disturbing wet soil results in large clumps that are difficult to break up later. Take a handful of soil and squeeze it. If it crumbles the soil is dry enough to dig. If it stays in a ball the soil is too wet.
Dig a 12 inch wide, 12 inch deep trench. Set aside the soil you’ve removed.
Break up the soil in the bottom of the trench using a spading fork or shovel.
Spread a 2 to 3 inch deep layer of organic matter (see below) on the rest of the bed.
Dig another 12 inch wide, 12 inch deep trench adjacent to the first one. Put the soil from the second trench, which includes the newly added organic matter, into the first trench on top of the loosened subsoil. Remove any rocks or debris. Break up the subsoil in the second trench as above. Repeat until you’ve dug the entire bed. Put the soil you set aside from the first trench into the last trench.
Add another layer of organic matter over the entire bed. Mix any nutrients needed into this layer, then turn it over into the top 6 inches of the bed.
This process will raise the level of the soil by at least 6 inches. In subsequent years, repeat only the last step. Never walk on your improved soil.
The best organic matter to use is compost. I don’t have a compost pile, so I buy “compost plus cow manure” or “cow manure plus humus” at the home center. It’s inexpensive, and easy to store because it comes in bags that can be moved around easily. Do not use fresh manure, which will burn plant roots. Peat moss is not recommended for the mountains because it will lower the pH on our already acidic soil.
This is hard work. Be certain you are physically able to do this, or hire someone who is physically fit with a strong back. But double digging is essential if you want to maximize production out of a small space garden.
The last column in this series will discuss planting techniques for your new raised beds.
Jim Janke is an Extension Master Gardener Volunteer in Haywood County. For more information call the Haywood County Extension Center at 828-456-3575. © 2019 NC State University.