Soil Preparation - Raised Bed Gardening - page 114

Chapter III Soil Preparation
Soil is a very complex subject. There are degrees in Soil Science and NASA devotes an en-
tire section to soil on their website. We don't need have a soil science degree to grow toma-
toes, but if we understand what makes better soil, we can grow more and better vegetables
or flowers.
Soil Preparation - Double Dig Method - Dig two shovel-lengths down. This requires the
top layer of soil be placed to the side so you can reach the next layer down. If you want to
keep the area clean, place the soil on a tarp ( Figure 65 and Figure 66 ), landscape fabric or
large pieces of cardboard. Then dig the second level of soil, which can stay in place or be
removed( Figure67 ) tomakeiteasiertomix.Eitherway,thesoilneedstobeturned,broken
upandmixed well withcompost and/orsphagnummoss( Figure68 ).Ialsoaddedtopsoilin
my beds because it contains sand, which is in addition to compost, also helps break up the
clay soil.
Start addingtheoriginal soilbackintothebedandmixmorecompost asyougo.Depending
upon how serious you get, this will mix, aerated and add fresh compost into soil from 1-2
feet deep. The more time and effort you can afford, the better.
Since my underlying soil has so many clods and rocks, I build a frame and attached ½ inch
welded wire with furring strips and screws. ( Figure 69 ) . The screen removes all rocks, clods
andstickslargerthan½inch.Alittlepoundingonthethelargerclodsbreaksthemintosmal-
ler pieces and allows them to pass through the screen.
You can add compost until the soil mix is at or very close to the top of the raised beds. Over
time, the soil level will settle again.
Since the soil line on my raised bed was about four inches from the top before I started dig-
ging,Iestimate thebedcouldholdabout16.5cubicfeet(CF)ofnewcompostandothersoil
amendments. In the process of double digging, I removed another 2 or 3 CF of large stones.
During the mixing process, I added about 20 CF of compost, sphagnum moss and top soil
into the bed, but when I finished adding, mixing and putting all the removed topsoil back
in the bed ( Figure 70 ), the soil is rounded off above the level of the raised bed. I estimate
the mixing process added about 15 CF of air space into the soil. So plan accordingly, just
removing and replacing the same soil will add about 4 inches to a 50 square foot bed.