One of G2's early decisions was to figure out how best to work the research plots at the farm. The subsurface geology under the farm resembles a piece of corduroy --- narrow limestone ridges approaching or emerging from the surface separated by 75 to 150 ft wide strips of deep rich limestone soils (Hagerstown silt loams).
Here's a picture from the year in which we purchased the property (2006). You can see the effect of the ridges approaching the surface in the alfalfa field next door. Those same ridges occur all across the farm, although the greenhouses are now built atop the ones that are most visible in this image.
Our silt loams actually have a fair amount of clay in them, too. That clay creates the potential for a plow-pan or hard-pan layer at the field depth where a moldboard plow cuts through the soil. When the soil is relatively moist, that shear-zone becomes compacted to the point where water does not penetrate, and this can cause both drainage issues as well as root zone growth and aeration issues.
If we were farming on a large scale, we could use chisel plows and subsoilers to break up the plow-pan. We could do most of our planting no-till, and avoid the creation of plow-pans. But ...
We were doing small plot work. Our typical plot is about 80 x 120 ft, approximately one-quarter acre. There is no way to use large-scale farm equipment in plots of this size, and have the whole plot be of uniform tillage. If the plots are not uniform, how can you adequately evaluate differences between varieties growing side-by-side in the field?
The prior owner was a small farmer who did routinely use a moldboard plow as well as walk-behind roto-tillers, which can also create a very similar plow-pan / shear-zone layer. We could also see surface puddling after heavy rains which lead us to suspect a subsoil problem. We could actually see the layer when we took a shovel and dug a foot down into previously cultivated fields.
So, we wanted to avoid small moldboard plows. We also wanted to avoid large tractor-mounted rotary tillers for the same reason. As we looked around for alternative small plot tillage implements, we came across a reference for something called a spader. These look like a tractor-mounted rototiller, but rather than having tines rotating around a shaft, they have small spades / shovels mounted on a cam-shaft so that the action is a push-and-flip --- just like using a hand spade --- rather than going around.
Here are two images, one of Andrew driving the spader across a cover-cropped field, and a second as a close-up of the spader in action.
Where did we find such a device? In Ontario, Canada at Timm Enterprises. The spader is actually manufactured in Italy, by a company named Gramegna. There are other vendors distributing Gramegna --- you may want to find someone closer to your location. That said, we are happy with Timm --- we have to replace the spades every other year so our relationship is on-going. I've often wondered about facing the edges of the spades with a harder tool steel but have not yet attempted to do so. We're on the edge of coal-mining country, where it is common practice to weld a harder metal onto the cutting edge of digging equipment.
There are other manufacturers of spaders out there. All seem to be European in manufacture.
For us, the decision was NOT to till. We are extremely happy with the results we see from using the spader. The first year out, we were digging up large clumps of plow-pan on a regular basis. Now, between the use of the spader and our routine use of deep-rooted cover crops, we rarely find remnants of moldboard / tiller damage.
As you can see, we're using a small Kubota tractor (34 HP) to drive the tiller. Although we wondered if we were under-powered for the spader with this tractor, we've had no problems whatsoever. We can take the spader into a field of sweet corn, and turn full-height green stalks into the soil. That said, usually and for our convenience, we do typically take a bush-hog across the field first. But the spader can handle mature green cover crops without much problem. We go back a week or so later; spade a second time; and have a wonderful surface in which to plant, whether transplants or seeds.