Ahh, March. Snow is still quite likely, but on some days our intense, high elevation sunshine beckons me into the garden. There, I’m greeted by one of my favorite smells—the aroma of humus-laden soil. The ground is no longer frozen. Let the growing season begin!
I’ve had my current garden for twenty years now. In that time, I have never stepped on the soil in my boxed beds. After an initial double-digging, the soil remains uncompacted, perfect for planting. Additionally, a soil test last year showed that I have plenty of humus—too much, actually—so I don’t even need to add compost for a while. Aside from adding a side-dressing of nitrogen, I won’t have to dig this year.
Previously, I did any needed soil preparation in the fall. Organic sources of potassium and phosphorus take time to break down and become available to plant roots, and are best added at the end of the growing season. Compost has time to continue decomposing into humus, feeding soil organisms. Alternate freezing and thawing further break up any hard clods of dirt, leaving soil friable. Adding a thick layer of mulch prevents compaction, leaving your garden ready to plant when warm weather arrives.
You can still dig now, of course. The important thing is to wait until your soil’s moisture content is just right. While sand is pretty forgiving, clay is not. Squeeze a lump of soil in your hand. If it crumbles, you’re good to go. But if it sticks together, digging will ruin your soil structure. You’ll end up with unbreakable, rock-like lumps of clay that will take years to correct. And if you think adding compost will eliminate the problem, remember that adobe bricks are composed of clay and straw!
My preferred digging tool is a spading fork, probably because it seems to spare more earthworms. A shovel is fine, as is a rototiller. (Be aware that repeated use of traditional rototillers, those with L-shaped blades, can create an impermeable “plow pan” under your soil.) Whichever implement you use, dig as deeply as you can manage. Eight inches is minimal, two feet deep is awesome.
If you need more humus in your soil, add an inch or three of compost, along with any fertilizers you need (check your soil test results). Rototillers make the work much easier, but don’t get over-zealous. Pulverizing your soil can cause it to pack down as it settles, making it hard for air, water, and roots to penetrate it.
Since I can skip all the digging, my next job is to warm up the beds that I intend to plant first. First I rake off the straw mulch that protected my soil all winter, so the sun can do its job. I may decide to lay down some plastic to hasten the process. Black plastic heats the soil while blocking light from reaching any exposed weed seeds. Clear plastic does a better job of warming, but allows weeds to germinate underneath. I choose IR (infrared) plastic… it’s black in color, but warms as well as clear plastic, plus a zillion tiny pinholes allow air and water to penetrate the soil. Later, I’ll plant right through it.
Finally, I wait. My soil thermometer will tell me when to plant. More about that next month.