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The Shrinking Coulter: When Heavy Metal Goes Underground

September 9, 2013

By Farmer John Peterson

Originally published on the Angelic Organics Farm News, Harvest Week 13. Angelic Organics is a biodynamic community supported agriculture farm (CSA) in Caledonia, IL.


We do deep tillage on the farm, every vegetable field at least once, sometimes twice per season. Our subsoiler (in some circles referred to as a ripper) penetrates the silty clay soil about 16 inches deep, slicing a channel through it which lets air in to stimulate microbial activity and lets water infiltrate, rather than pool on the surface or run off. In loosening the soil, the tillage machine makes it easier for roots to penetrate and spread out. It takes a lot of power to subsoil (hence the term rip), about 35 horsepower per shank.

Hardened steel points are bolted to the tips of the subsoiler shanks. There is a variety of point styles that a farmer can choose from, depending on how aggressively he wants to loosen and lift the soil. The points we use at Angelic Organics lift the soil just a little, not nearly so much as a mole making a classic burrow in a cartoon.

The subsoiler has coulters mounted on the front that slice through the ground ahead of the shanks, cutting through crop residue that might otherwise plug the machine. Our coulters had become badly worn over the years, so Primo replaced them this past week.

Soil is much softer than steel, yet the soil can shape the steel, wear it down, transform it. It makes one aware of what love can do in hard places.

The new, black, waffle coulters are positioned ahead of each shank. We also replaced the points on the tips of the shanks.

The new, black, waffle coulters are positioned ahead of each shank. We also replaced the points on the tips of the shanks.

The new coulters are in the foreground. The old coulters are in the background. The old coulters were originally the size of the new coulters.

The new coulters are in the foreground. The old coulters are in the background. The old coulters were originally the size of the new coulters.

Overlay of the old coulter (shined to a silvery finish from slicing through the soil over the seasons) on top of the new black coulter. The old coulter is about 13 1/2″ in diameter; the new coulter is 17 1/2″ in diameter. The soil wore the old coulter down 4″ in diameter over the years.

Overlay of the old coulter (shined to a silvery finish from slicing through the soil over the seasons) on top of the new black coulter. The old coulter is about 13 1/2″ in diameter; the new coulter is 17 1/2″ in diameter. The soil wore the old coulter down 4″ in diameter over the years.

Rear view of the subsoiler shank, which penetrates about 16″ into the ground. Notice how the shank tapers from the top, where it is about 1″ thick, to about 1/2″ towards the bottom. This tapering is from slicing through the soil acre after acre, year after year, and is exacerbated by the occasional rock.

Rear view of the subsoiler shank, which penetrates about 16″ into the ground. Notice how the shank tapers from the top, where it is about 1″ thick, to about 1/2″ towards the bottom. This tapering is from slicing through the soil acre after acre, year after year, and is exacerbated by the occasional rock.

Angelic Organics - shank guards

Primo eventually intervened with the wear on the shanks by installing shank guards, which direct the soil wear to the shields and away from the shanks themselves. Here you see the worn point and shank guard in the foreground, with the new point and shank guard just behind it. The point and shank guard in the foreground were originally the same size as the point and guard behind them.

2 Comments leave one →
  1. September 9, 2013 11:40 am

    Very odd, with so many farmers going to NO till. What’s up with “destroying the soil food web”?

    How is this biodynamic?

    • Thea Maria Carlson permalink*
      September 25, 2013 8:08 am

      Thank you for your comment Christine. Tillage is used quite frequently on nearly all organic farms, and is not necessarily bad for the health of the soil when used in a balanced way combined with other good management practices. Unfortunately, many farmers who practice “no till” are only able to do so by spraying large amounts of herbicides, which can be very damaging to the life of the soil. There have been strides toward developing non-chemical methods for reducing tillage, as outlined in this bulletin from the Rodale Institute. As our board president Jean-Paul Courtens illustrated in his recent article, farmers must constantly strive to find the right balance of “nature” and “technology” on their farms, and tillage is an important aspect of that balance.

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