Preparing the Soil

By Chris Blanchard, Rock Spring Farm

From the perspective of the getting crops into the field, the flooding we had in June couldn't have happened at a worse time. We had already had several days of rain that kept us out of the field, and the addition of twelve inches meant that seeding and transplanting fell way behind. As a result, the following two weeks were a frenzy of getting things in the field.

Crops get into our fields in one of two ways. We either place the seeds directly in the ground or start them in soil blocks in the greenhouse and then set the started plants out in the field. But before we do that, we have to prepare the soil for planting.

The steps for preparing the soil for planting depend on the condition of things when we start. If we have a tall cover crop growing in the place we plan to plant, we'll mow that first with our flail mower to chop it into little bits. Rather than one large blade rotating horizontally around a vertical axis, a flail mower has multiple small, swinging blades that rotate around a horizontal axis. Like almost every other tool we use in the field, it fits on the back of our tractor using a universal three-point hitch; the tractor powers it by way of a shaft that fits on the tractor's power take-off, or PTO for short.

Wet, green vegetative stuff has a lot of nitrogen loaded in it, and adding all of that wet nitrogen to the soil can set off a real flush of biological activity, kind of like a sugar rush. We like to wait a day before tilling in the shredded cover crop. To till in the residue, we use a rototiller. This is pretty similar to your basic garden tiller, except ours mounts on the tractor; it's five feet wide. Because too much tilling can really destroy the soil structure that encourages optimal biological conditions, we spent extra money for a tiller with four different rotating speeds, so that we can do just as much tilling as we need to do and no more. Our tiller also has a very fine depth control, so that we don't have to till any deeper than absolutely necessary. In fields where we have trouble with perennial weeds, we till about four inches deep; by leaving the back of the tiller open, we are able to toss the quack grass and thistles up on top of the soil, where they dry out and die. In our other fields, we often till just two inches deep, so that we don't bring new weed seeds to the surface of the soil to germinate. Generally, for this tilling pass, we travel at about two miles per hour, which gives the tractor driver plenty of time to think.

After tilling in a cover crop, we like to let at least three weeks or even a month go by before we plant anything; otherwise, the soil microbes just see the seeds as more food, and will devour them along with everything else they are breaking down. Also, big chunks of straw and root-filled clods are difficult to work with using our tractor-mounted seeders, making the work of the transplanting crew much harder than it needs to be.

Just before we plant, we come back with a finishing pass of the tiller to break up any remaining organic matter, bury clods, and leave a fine finish. This pass releases the most of that wonderful "earth smell" that you get from plowing or when rain falls after a dry spell of weather.

If we don't have to incorporate a cover crop, or if the cover crop died over the winter, the way oats do, we can till and plant in the same day. But ideally, we would till once to loosen things up, then come back with a skimming tilling pass a day or two later to break up any chunks left behind. A little bit of rain can mellow the soil quite nicely once it's already loosened, allowing small clods to break apart into fine soil.

The fine finish has two main advantages. First, since most vegetable seeds are small compared to something like corn or beans, it allows the seedlings to emerge without running into a big clod that can impede their progress. Second, a fine soil means that weed seedlings can't bury their roots in a clod that won't break apart easily when cultivated; if a weed can hold on to any moisture at all, it just might survive.

That intoxicating earth smell you get during this pass can also be like the sirens that lure sailors onto the rocks: beautiful and almost too tantalizing to leave behind. It can be tempting to till and till, until the soil turns to a fine powder; unfortunately, over-tilling can leave soil vulnerable to wind and water erosion, as well as causing a crusting effect that makes seedling emergence difficult and soil-drying almost impossible. The same can happen simply by leaving soil exposed to the elements for too long, which leaves us with the constant juggling act between flexibility—open soil, ready to plant at a moment's notice—and soil quality. Choosing soil quality leaves us more vulnerable to the vagaries of the weather, since we need more lead time and more passes to plant, but it preserves and builds the soil, and, ultimately, provides more flexibility since healthy soil both holds and drains water better, besides providing a better growing environment for healthy plants.

Follow the growing season and get great seasonal recipes at the Rock Spring Farm blog, www.eatbetternews.com