More Manure, Less Ecological Destruction

Poop Not Peat

As spring arrives, homeowners happily load up on giant bales of peat moss. Though these well intentioned folks certainly don’t know they are participating in a destructive practice, the continuing use of peat moss damages natural boggy habitats for a surprisingly long time. Visit a bog where peat has been mined for a century and you’ll see the oldest cuts looking nearly as fresh as the newest. That’s because bogs, like tropical rain forests, can take hundreds of years to recover from extractive and damaging practices like mining and logging. Sphagnum peat moss can only be harvested by destroying boggy natural habitats. The worst of this is the irony that peat moss isn’t helpful for our soil or plants.

Most folks don’t realize this, including a surprising number of people in the nursery business. For starters, peat moss has very little nutritive value, so it’s not in any sense a fertilizer. Unlike compost, peat moss degrades too fast to be an effective soil conditioner. It is very acidic, which does not help balance our already acid Northwestern soils. In fact, peat moss is so acidic that it can kill bacteria, which is why sphagnum moss was used as bandaging material for centuries (maybe millennia). Wounds packed with clean sphagnum moss had a better chance of healing cleanly, and it was even used in field dressings for wounded British troops during WWII.

Once Dry, Dry Forevermore

I’m especially upset when I see peat moss recommended because it holds water so well. In its natural state, yes. Once dried out, not so much, since it becomes an impervious, water-shedding (rather than water-conserving) mat. That’s why it should never be used as a top dressing, that final layer of a garden bed, usually consisting of an inch or two of fine textured mulch such as compost or aged dairy manure. Ideally, this layer conserves moisture, suppresses weeds, and promotes rapid root growth. Peat moss clearly makes a horrible top dressing and is a remarkably poor mulch as well. Peat is very difficult to rewet in garden soils and peat based potting mixes, which is annoying and very hard on plants. Peat based potting mixes are light in weight, which is good if you are carrying the pots around, but also means wind can rock plants easily, distressing the roots.

More Problems With Peat

In its natural environment, peat moss is highly acidic and nearly sterile, but by the time it is dried and baled, it can harbor spores of fungal diseases that has proven to be dangerous to handlers. Nursery workers are warned by law to wear double gloves and micron filtration masks when handling peat moss. The gardener is not told anything, yet those who handle peat moss regularly are at risk for fungal pneumonias and other illnesses. Worst of all in my mind, peat moss is not a renewable resource. Bogs are delicate, intricate environments that host a great and beautiful diversity of living fauna and flora. When bogs are destroyed by peat mining, companies are now forced to “restore” them, but to date, the artificial, “managed” bogs never achieve the biodiversity of the original habitat.

If peat is not a truly renewable resource, compost certainly is, and compost offers excellent soil conditioning as well as a slow, steady supply of nutrients. Leaves, which many of us receive for free in abundance each autumn, and which break down into good quality composts, are also renewable (as long as we respect nourish our life-supporting trees). And when it comes to renewable, not much is more consistently produced than manure. However, it does matter which manure we choose. Initial testing of various kinds of animal manures at Oregon State University in Corvallis show that animal manures vary widely in their qualities. Horse manure, for example, is often contaminated with worming agents that continue to kill worms in compost and soil after passing through the horse. Horse manure mixed with bedding may contain clopyralid, a long-lasting pesticide that remains active indefinitely (it especially affects legumes, nightshades, and composites, which covers a lot of floral ground). Steer manure is gathered from stockyard holding pens, where salt licks encourage animals to drink lots of water. The resulting manure often has a very high salt content, which can burn young plants and seedlings. Steer manure is very apt to contain hormones and steroids as well.

What The Right Doo Can Do

Instead, I use aged dairy manure as a soil amendment and as top dressing. Recent research indicates that a mulch of dairy manure can slow down or even halt the growth of certain soil pathogens, notably several root rots that are prevalent in the native soils of the Northwest. Aged manures are especially valuable in the garden, especially when “washed”. In most modern dairies, the barns are washed down daily and the manure accumulates in holding pits. The nitrogen-rich effluent is drawn off and returned to the fields where alfalfa and other fodder is grown. The washed manure is sold as an excellent soil amendment. Dairy manure from an organic dairy will not contain bovine growth hormone, steroids, or other “prophylactic” medications.

Digested cow manure is another valuable renewable resource with several benefits. In some places, pit washed dairy manure is trucked or piped directly to an anaerobic digester facility, where the methane is stripped out and converted to electricity, which gets sold to local power companies. Anaerobic digestion produces biogas (mainly methane and carbon dioxide) by composting organic materials in an oxygen-free environment. When manure breaks down outside, the biogas becomes a ‘greenhouse gas’, but when it’s captured in an anaerobic digester, the result is clean power and a big pile of digested poo. It’s not exactly like aged, composted manure, but it has similar nutrient levels, low pathogen levels, and is an excellent soil conditioner. Because it is not as aged, it does smell more ripe, as holiday visitors to my home have noted.

How Do We Get Some?

Anaerobic digesters are hardly new, but today’s technology makes them far more efficient. In Washington State, dairy coops share local digesters to create energy and manage their mounds of manure. It took time to figure out how to get that end product into gardens, but today, you can buy it as bags of Magic Dirt, USDA certified, biobased potting soil that has been approved for organic growers by the Idaho Department of Agriculture and the Mulch and Soil Council (bet you didn’t know there was one!). Onward!