For Peat's Sake: Should You Be Concerned?

You probably know it as the best growing medium you can buy. Among its many benefits, sphagnum peat moss offers excellent water and air exchange capacity; provides ideal cation-exchange capacity; enhances root growth; provides excellent buffering capabilities; saves water by retaining moisture and releasing it slowly; saves on fertilizer by reducing nutrient leaching; protects soil from hardening; adds organic material; and aerates heavy, clay soil and binds sandy soil.

U.S. peat resources have been estimated at more than 110 billion tons, with more than 50 percent located in undisturbed areas of Alaska, according to the United States Geological Survey (USGS). Florida, Michigan and Minnesota are the highest peat-producing states, in order of quantity produced. In 2002, 760,000 metric tons were produced domestically, with 95 percent of that production absorbed by the horticultural industry. Peat produced in the United States is typically classified as reed-sedge Hypnum peat, which has a lower market value per ton than the weakly decomposed sphagnum peat from Canada. Ninety-nine percent of U.S. peat imports from 1998-2001 came from Canada, accounting for 50 percent of total domestic usage, according to Stephen M. Jasinski, a peat commodity specialist for the USGS.

World peat resources have been estimated at 2 trillion tons, of which the former Soviet Union has about 770 billion tons and Canada approximately 510 billion tons. The development of new horticultural peat operations or expansion of existing operations in the United States has become increasingly difficult, as numerous federal, state and local wetlands protection regulations apply to permitting, harvesting and reclamation of peat bogs. The cost of compliance and the time required to obtain the proper permits have caused some smaller producers to stop harvesting peat. The USGS anticipates that domestic peat demand will continue to grow at a steady rate for the near future, with Canadian peat accounting for a greater percentage of U.S. consumption.

Explaining peat

So just what is a peat bog, anyway? In short, it is a special type of wetland. A "peatland" is a wetland on which extensive organic material has accumulated, the rate of which can be as much as 1-2 mm per year (4-8 inches per century). Peatlands are defined by a minimum accumulation of 16 inches; as the peat layer accumulates, access to nutrients in the underlying soil is reduced such that the vegetation must obtain its nutrient requirements from groundwater seepage. Peat accumulation can occur when climatic and other physical conditions result in a rate of plant material growth that exceeds the rate of decomposition. Peatlands may have trees -- or not -- and species diversity tends to be low, most likely due to the acidic, low base cation environment.

Approximately 99 percent of Canada's total national production comes from the combined operations of 20 corporate groups that form the Canadian Sphagnum Peat Moss Association (CSPMA). The majority of these operations are located in southern and southeastern Quebec and eastern and northeastern New Brunswick. Once a peatland has been selected, it is surveyed and a drainage plan is prepared. Following the completion of ditches, surface vegetation is removed and the deposit is ready for peat production. Drying the surface peat layer requires the sun and wind -- which is why areas receiving high precipitation are poor selections for harvesting -- and the topmost layer is typically harrowed or "milled" to enhance the drying process. After 1-3 days, the dry peat layer is collected using a large vacuum harvester or other equipment, then is transported to a processing facility for screening and packaging.

Sustaining Peat

According to a 1999 International Peat Society (IPS) survey, Canada ranks second in global production of horticultural peat after Germany, producing approximately 22 percent of the world's horticultural peat. In Canada, harvesting takes place on less than 17,000 of the country's total 113 million hectares of peatlands, according to the issues paper "Canadian Peat Harvesting and the Environment," and as an overall resource there is 70 times as much peat accumulating as is being harvested each year in Canada.

When harvesting is completed on a bog, it is returned to a functioning peatland under Canadian governmental regulations. Before harvest, a producer must take all necessary steps to Á reduce impact on the environment; record the flora and fauna present on the bog for restoration purposes; and cooperate with local environmental groups. During harvest, the producer must minimize the acreage being harvested; leave a buffer zone around the bog; leave a layer of peat when harvesting stops; and design drainage ditches so the water table can be restored. The primary goals after harvest are to restore the bogs to wetlands and reclaim bogs for beneficial crops.

The arguments for peat sustainability in Canada are sound, and with governmental monitoring in place, Canadian peatlands will offer high-quality peat to North American suppliers well into the future. In Europe and especially the UK, however, the situation is quite different. Whereas Canadian peat is used almost exclusively for horticultural purposes, in the UK, 66 percent of harvested peat is burnt as fuel, while only 33 percent is used for horticulture, according to the UK's Peat Producers Association (PPA). A current government target requires that 40 percent of the UK market be replaced by peat alternatives by 2005, and it has been suggested that that figure be increased to 90 percent alternatives by 2010, inciting staunch opposition by the peat industry. At present, 40 percent of the peat used in the UK is produced domestically, while 60 percent is imported, primarily from Ireland.

Judging from the major impact that environmental groups have had on other industries in Europe, such as genetically modified seeds and food products, there is reason to believe that in the future, the UK's target for peat alternatives could conceivably increase beyond the 40 percent previously cited. Should that happen, there is the possibility that the country would have to look beyond Ireland for peat imports. That place could be Russia, Germany or Finland, but it could also be Canada -- which would drive up prices for U.S. importers as well as consumers.

Peat Alternatives

Michael Evans, an associate professor at the University of Arkansas, offers a good reason to consider alternatives: increasing the arsenal of growing media. "Hopefully, we'll find things that are locally and regionally available for growers to use effectively that are cheaper. If you look at what goes into a greenhouse operation, growers don't tend to have control over many costs--but one of the areas they could potentially tweak is in their growing media." Here are a few peat and perlite alternatives you may have heard of, and some others coming down the pipeline.

Coir. Evans has done a fair amount of research with one of the most common peat alternatives, coir. Composed of coconut hulls, coir works very well as a growing media component, although it varies from sphagnum peat in some of its properties. Most notably, it has a slightly lower air-filled pore space but a higher water-holding capacity. It also tends to have a higher pH than peat, reaching into the 5.0-6.0 range. High-quality coir should be brown, not green or yellow, which would indicate newer, fresher coconut; coir with a high proportion of new rather than decomposed material can cause nitrogen tie-up, according to Evans. Coir is also susceptible to higher salt levels both because coconut trees naturally extract salt from the soil and because of low-quality processing.

There are two things that Evans advises growers to watch out for when using coir. First, when it's wet, it should act like a sponge, not coffee grounds. Its consistency has to do with the compression ratio and moisture level the producer used when the coir was manufactured; if the material was too dry when it was compressed into bales or blocks, the tiny, sponge-like cells will collapse, and cannot re-expand. Good coir expands and absorbs water readily. Second, do a quick pH and EC test, in case you should end up with a low-pH batch.

In Evans' coir research, everything from poinsettias to bedding plants has performed similarly to those grown in sphagnum peat; there have even been reports of increased root growth with the use of coir and of fungus gnat control. Coir does seem to exhibit disease-suppression capabilities, particularly of Pythium and Phytopthora. Evans believes that some chemical compound is responsible for this characteristic, as coir is loaded with phenolic compounds -- the natural chemicals plants produce to defend themselves against disease. Unfortunately, the suppression Evans has seen has not been entirely consistent in experiments using ratios of 80 percent coir and 20 percent perlite.

Despite its benefits, there is no cost savings associated with using coir because it ships from such faraway places as Sri Lanka and the Philippines -- this is perhaps the one issue that has limited the growth of the coir industry for horticultural applications.

Compost materials. Kim Moore, an associate professor at the University of Florida's Ft. Lauderdale Research and Education Center, has focused on the use of compost materials, and particularly, on locally available sewage sludge combined with yard trimmings. "Something like compost is really a very good product -- it can replace part or almost all of the peat. What I like about it is that it has a lot of the properties of peat -- the water-holding capabilities and that beginning nutrient charge -- so I've found I can cut my fertilization back when I use the sewage sludge-type compost."

While Moore believes this type of compost holds a lot of potential, it also poses two setbacks. First, it can be difficult to get a consistent product every time, and second, it's not always locally available, which means the cost could be greater. Some growers in South Florida are using this product as a partial replacement to peat and as a supplement to fertilizer. Moore says she's been able to achieve plant performance of equal quality in her experiments with the sewage sludge compost compared to those grown in Pro-Mix or Metro-Mix.

Earthworm castings. At Mississippi State University, Associate Professor Richard Harkess has done extensive research with earthworm castings generated from horse, cattle and sheep manure. "Some plants did fantastic; in fact, most plants with 20 percent worm castings mixed in with peat moss and perlite did wonderfully. We even grew some poinsettias where we didn't have to fertilize the crop for the entire production cycle -- that was with a fairly high concentration of castings."

The type of worms used for their castings are Eisenia fetida, and are capable of consuming up to their bodyweight each day. The type of manure used does matter; for example, chicken manure is too high in ammonia, so worms will crawl out of it rather than into it, and hog manure is unpalatable for some reason -- in fact, in Harkess' studies, the worms would either avoid it, or they'd die within a few days. Horse manure contains high levels of undigested cellulose in it, which remains even after processing. "If you have a long-term crop, you're going to see your soil shrink [with horse manure castings]," Harkess commented.

Cattle manure is more stable than horse manure because the cellulose is thoroughly digested in a cow's four-chambered stomach; however, because cows extract most of the nutrition from their food, the resulting castings tend to be less nutritionally dense. Plants in Harkess' experiments still grew successfully in cow manure castings despite their lessened nutritional value.

Growers can produce their own earthworm castings with the help of a large bioreactor designed for culturing these worms. "You put fresh manure in, usually about an inch at a time, and as the worms consume it, you add another inch, and the worms consume it, and you take the finished castings off the bottom," Harkess explained. There is also the possibility of an industry being created for these castings. Harkess says he could imagine this being in cooperation with a feedlot somewhere or a local stockyard. "This market is untapped and undeveloped in a lot of ways. Plants respond very well to it, and castings fit into the whole organic gardening movement," he said. 

Fresh rice hulls. While you've probably heard of using dried rice hulls as a soil amendment and alternative to perlite, you may not have thought of fresh ones -- perhaps because there is a standing opinion that they cause nitrogen tie-up. In Evans' trials with geraniums, tomatoes and pansies, however, there have not been any nitrogen issues. Rice hulls are almost entirely silica, with a small amount of lignan. They have a higher air-filled pore space, provide more drainage and are much cheaper than perlite. Aside from all that, fresh rice hulls are abundantly available as a waste product, with virtual mountains of them in Arkansas, Louisiana, Mississippi, Texas and California. "We've replaced perlite with fresh rice hulls, and it's working beautifully -- plants do very well in it. Regardless of what they come up with in price, it's going to be a lot cheaper than perlite," Evans said.

Keeping your options open

You may be more than satisfied with your crop performance using sphagnum peat moss products, and Canadian producers' efforts to keep peat bogs sustainable should allay any environmental concerns you might have. Nevertheless, it's important to remember that amid all of your fixed costs, you still have options when purchasing your growing media. There are some viable alternatives out there that may help you save money while maintaining the same quality that peat has afforded you -- and at the same time, help you turn waste into something useful.