The Harvest of Peat!

Peat is partially decomposed plant matter that has accumulated in low-lying depressions. When extracted from the ground surface, peat is valuable for uses such as microbial carriers, water treatment media, soil amendments and turfgrass soil mixes. Most operators who extract peat use the term “harvest” to refer to their activities. At first glance, that may seem to be a misnomer, but there are many similarities between peat harvest and more typical agricultural harvest methods.

Perhaps the greatest similarities are found in green Sphagnum harvest. Sphagnum is a common peatland plant with remarkable water-holding characteristics. As a result, it is a valuable soil amendment and horticultural aid. Sphagnum can be harvested by snipping off the topmost ten inches or so and drying it to reduce the water content. If the harvest depth is correct, the plant parts that are left behind will regenerate and return the Sphagnum level to pre-harvest elevations.

The regrowth period is measured in years, not months, and currently, green Sphagnum is not a highly marketed product. But green Sphagnum can replace up to 100 percent of peat moss in growing media without losing any benefits. That makes it an attractive, more sustainable soil mix amendment.

Vacuum peat harvest is somewhat similar to green Sphagnum harvest, except it removes the already-dead Sphagnum plant that has become peat. When opening a new peatland for harvest, the operator will remove the live plants and topmost surface and store it nearby for use as a reclamation material. Then, on an annual basis, the peat surface is disked to “fluff” up the surface. If the weather cooperates, the sun and wind during the warm weather months will dry that top surface to the point where the peat can literally be vacuumed off the field. Vacuums are most commonly used in Sphagnum peat harvest because the peat tends to be lighter and more fibrous than reed-sedge peat.

The amount of peat that can be taken off the surface is usually dictated by regulations. Once the maximum harvest has been achieved, a Sphagnum peatland is often restored using the moss layer transfer technique. In that technique, the hydrology is restored as much as possible, and then plant fragments collected from a nearby source are spread over the surface. A thin layer of straw, and occasionally a light fertilizer dressing, are added to protect the rooting plants and give them a boost. The moss layer transfer technique is remarkable in its simplicity and success rate. Vegetation cover of up to 50 percent in three years is common, with hummock Sphagnum species well established within 20 years.

Reed-sedge peat can be harvested by vacuum, but it is more difficult than Sphagnum harvest because reed-sedge peat tends to be less fibrous. At American Peat Technology, we use full-section excavation to harvest the peat during the winter months. Because we’re operating on a prior-converted peatland, our harvest area already resembles a farm field. We remove the entire peat profile with an excavator, leaving behind enough residual peat to support reclamation efforts. When the next spring comes, snowmelt drains into the harvested area and contributes to the size of a growing wetland.

We follow harvest with multiple reclamation methods to establish or encourage native plants. Unlike Sphagnum systems, reed-sedge peatlands do not lend themselves to the moss layer transfer technique. Revegetating reed-sedge peat is more akin to gardening. Seeds and seedlings are applied and nurtured to encourage quick growth. All while trying to hold invasive species – the weeds – at bay.

The end result of our revegetation efforts will be a shallow wetland ecosystem with native species such as wild rice, sedges and willow. Invertebrates, fish, birds and mammals already use the wetland, and as the wetland matures, it will become even more valuable. Considering that we’re harvesting prior-converted peat that has been farmed for nearly a hundred years, APT’s harvesting operations result in a more diverse and natural ecosystem that not only builds new peat accumulation but also provides ecological benefit in the process.