No To Peat Moss, Yes To Dairy Manure

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Sustainable Manure, Land Raped Peat Moss

I find it heartbreaking to see well-meaning people buying bales of peat moss. Old-think gardening promoted peat moss heavily, but all forms of sphagnum peat moss are harvested by destroying boggy natural habitats. Worst of all, this is truly senseless destruction, because peat moss isn’t helpful for our soil or plants.

What??? Yup!!! For starters, peat moss is very low in nutrients and it degrades too quickly to be an effective soil conditioner. In addition, it’s 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 still used for British troops during WWII.

Peat Moss Damage And Dangers

Besides all that, peat moss makes a horrible top dressing. Top dressing is the final layer of a garden bed, usually consisting of an inch or two of fine textured mulch such as compost or aged dairy manure. This layer conserves moisture, suppresses weeds, and promotes rapid root growth. Though often recommended, peat moss also makes a remarkably poor mulch, drying to an impervious, water-shedding (rather than water-conserving) mat in no time. Once dried out, peat is very difficult to rewet in garden soils and in 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.

Though fresh peat is highly acidic, when dried and baled, it can harbor spores of fungal diseases that can 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 use peat moss regularly are at risk for fungal pneumonias and other illnesses.

Sustainable And Not So Sustainable

Finally, peat moss is not a renewable resource except in glacial terms. If you visit bogs that have been harvested for many years, you can see plainly that cuts made a century ago have barely begun to heal. Bogs are delicate, intricate environments that host hundreds of living fauna and flora. When bogs are destroyed by peat mining, companies are now forced to “restore” them, but the artificial, “managed” bogs never achieve the biodiversity of the original habitat. I’m not alone in this anti-peat campaign; Here’s a link to Ken Druse’s article on peat moss:

If peat is not a truly renewable resource, manures definitely are. One thing we can count on is that poop happens. 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).

Washed Or Digested?

In stark contrast, aged dairy manure makes an excellent soil amendment and/or 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. Most modern dairies have holding pits where manure is stored. The barns are washed down daily and the manure accumulates in the 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 a splendid soil amendment. Dairy manure from an organic dairy will not contain bovine growth hormone, steroids, or other “prophylactic” medications.

Digested cow manure is what’s left over after manure is mined for energy. Dairy manure solids (often mixed with field crop waste) are trucked to an anaerobic digester facility, where the methane is stripped out and converted to electricity, which gets sold to local power companies, partly offsetting trucking costs. 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.

True Power Of Poop

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.

Here’s more about digested manure:

To find digested dairy manure in your area, contact your local Agricultural Extension agent. If you live in Western Washington, you can try Mark Vukich, who delivers both pit-washed dairy manure and digested dairy manure:
Mark Vukich
Moo Doo For You
(206) 271-6490
(253) 939-0627

If you aren’t near a digester, look for digested manure potting soil:

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5 Responses to No To Peat Moss, Yes To Dairy Manure

  1. Patricia says:

    I remember that years and years ago, you were one of the first prominent garden writers to challenge the glib use of peat moss and the practice of double digging. Your advice remains timely!

  2. Hi Ann, thanks for this post, which my mother forwarded to me. I’ve been thinking about this issue a lot recently.

    Firstly, I haven’t yet found a good substitute for sterile seed-starting mixes. The Sunshine mix containing peat seems to be pre-wetted so hydrating flats of seeds is fairly straightforward. [The pre-wetter is probably the saponin from Yucca, so not too bad.] I usually make my own seed starting mix, loosely using the Eliot Coleman recipe, and sieving everything through my 1/8″ screen. I make about 2-3 cubic feet at a time and do not sterilize it. Unfortunately, the (admittedly, only one) bale of coconut coir I bought was filled with large sticks and plastic threads and was very unsatisfactory. I have never found rice hulls available, but will now seek them out. I’m looking forward to trying out Magic Dirt; I appreciate the reference.

    Secondly, the bagged (convenient for container work at clients’ homes) potting soils available at our garden centers both contain peat. Interestingly, they’re a bit green-washed, one indicating it is organic, and the other “all natural”. Admittedly, I have to justify buying bagged soil and having the waste-problem for the bags, but the manufacturers claim that the bags are “poly 4” and thus recyclable if washed, in most large municipal recycling centers.

    Finally, do you have a reference to dried nursery-grower’s peat containing fungal spores? The MSDS on the Edna’s Best and the SDS of Gardner and Bloome’s potting soils only indicate the use of gardening gloves, and a mask to avoid nuisance dust.

    Thanks for a thoughtful post.

    • Ann Lovejoy says:

      Well, hmmm, I am not aware of any commercial seed starting mix that does not contain peat moss (or open pit-mined perlite), so make my own by mixing screened compost and composted dairy manure with sandy loam. I think you would find that aged digestate would work beautifully too; I’m using that in my seed mix this year and so far, results are excellent germination and early stage growth.
      For wetting agents, consider making you own with seaweed. Here’s a link to a recipe I’m now trying myself:
      As for the peat moss workers lung issues, here are some links to explore (there are many more; it is periodically a hot button industry issue as outbreaks get in the news, then the buzz typically cools off)

      • Thank you for the references, especially the NIH ones. For some reason, I didn’t get notified on this post, so sorry for the delay.

        Not that I recommend it, but it seems that one study you cited found a protective effect of smoking for “peat-moss lung”. And, I would suspect that being a Viking or a Pict would have been detrimental, since they used to heat their homes by burning peat-bricks. In all seriousness, the ATS Journal reference was quite good.

        I did some cursory research and found that rice-hulls are high in silica, and thus are probably a better functional replacement for vermiculite than for peat, however they do have reasonable water-holding capacity. Since they are a renewable, organic resource that would otherwise be wasted, using them up to 50% peat replacement seems like a good idea.

        Given Coleman’s recipe of 3X peat : 2X perlite or sand : 1X garden soil : 2X compost, an alternative might be substituting 1.5X rice hulls : 1.5X coir for the peat component, and no need to add lime since the rice hulls are not as acidic as peat. The MooDoo would be a great substitution for the compost component. I think I’m going to need some more galvanized storage containers!

        • Ann Lovejoy says:

          I’m very happy with the digested dairy manure I’ve been using for the past year. It doesn’t need anything added to be a marvelous soil conditioner and is also great as a top dressing. It does need to age before using, though, as it comes fairly hot (the biogases are removed in the electricity production process, but most nutrients remain).

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