Gardeners will either buy gardening soils as needed and/or make their own soil via composting. Other than using the precautionary measure of wearing gloves and washing all plants thoroughly before consuming them, it likely doesn't make economical sense for gardeners to allow their purchased soils additional time for curing.
However, when composting to make your own soil, it's important to practice proper composting to prevent the transfer of parasites from our gardens to our bodies. When manure decays it turns into compost just like any other organic matter. The compost decays further into humus. After two years of decay, the manure compost has lost all of its very bad elements such as parasitic worms, and if you use common sense hygiene, it is no different from handling compost made from decaying leaves except that it is a lot richer in nutrients.
Hazards Found in Soil
Bacteria and Fungus
Soil naturally contains many type of bacteria and fungi which can cause diseases such as tetanus, botulism and histoplasmosis. It is extremely critical to avoid contact of soil with any wounds and to prevent soil from making contact with your mouth or nose to prevent entry of parasites. That may sound obvious, but be sure to wash all your produce well and be careful about brushing away pests from your facial area while working in the garden.
Using Animal Waste in Compost
This includes both wild and domesticated animals and include either feces or carcasses. Often pathogens from domesticated animals such as cattle, are often deliberately introduced to a site in raw or improperly composted manure. This could potentially contaminate soil and ground water with both bacterial and/or protozoan pathogens.
Cattle manure is basically made up of digested grass and grain. Cattle dung is high in organic materials and rich in nutrients. It contains about 3 percent nitrogen, 2 percent phosphorous, and 1 percent potassium (3-2-1 npk). However, cattle manure also contains high levels of ammonia and potentially dangerous pathogens. For this reason, it’s usually recommended that it be aged or composted prior to its use as cow manure fertilizer.
Horse manure may be available in some areas. It produces poorer quality compost, but is generally regarded as presenting a lower health risk. However, manure that has been gathered from stalls is often very high in ammonia. Either avoid manure sourced from stalls altogether or be sure it has aged for a minimum of two years or it will burn plants to the point of death. As for hazards in horse manure, a soil bacterium, Rhodococcus equi, found in horse manure, has become of increasing concern as the cause of a severe form of pneumonia in persons having a compromised immune system through AIDS, immuno-suppressive therapy, and other similiar situations. Infection can also occur through inhaling dust contaminated with dried manure.
Recent research also raises concerns about Giardia which occurs in horses. Only certain genetic subgroups of this protozoan parasite have been associated with human disease, and the presence of one of these has been identified in samples of horse manure. Giardia causes bloating, diarrhea and nausea, which can be especially protracted and debilitating in susceptible individuals.
It is generally not recommended to put the feces of meat consuming animals into composting piles because of the additional complexities of potential disease as well as it is quite difficult to decompose for the average backyard composter. Dogs and cats are also among other potential animal sources of human infection with Giardia. Nationally there are approximately 2 million cases of Giardia annually most of which involve contaminated water, but CDC estimates 10% to be food borne.
Other potential sources of contamination include waste from wild animals and birds, especially pigeons and gulls. Reptiles such as lizards, snakes and turtles are a well known source of Salmonella. Just handing the surface of an object these animals have been in contact with is enough to potentially cause contamination.
What can be done to reduce bio-hazards in soil?
One simple precaution relative to manure is that should never be used raw – apart from health concerns, it can burn plant roots. When composted, manure has to reach temperatures above 140ºF for at least 5 days to ensure destruction of bacteria such as the potentially deadlly strain of Escherichia coli (E-coli) which causes severe disease, especially in children and is principally found in cattle manure.
It is imperative that at-home compost piles reach the minimum 140 degree temperature for 5 days to destroy the pathogens found in animal manure. Many other bacterial/protozoan pathogens are present in animal manure. In residential areas composting should be limited to plant and none-meat kitchen waste. Heavy manures, like that of cows and horses, should be mixed with lighter materials such as straw or hay (this is where the manure from around the goat manager works great) in addition to the usual organic substances from kitchen vegetable matter, garden debris, and other plant based sources. Small amounts of lime or ash may also be added.
An important consideration when composting materials is the size of your bin or pile. If it's too small, it won't provide enough heat, which as stated above, is critical to safe composting. Too big of a pile will be difficult to turn and therefore the material may not get enough area. Regardless, frequent turning is a requirement.
- One of the most common methods for plants to cause infection in humans is through consuming plants without properly washing them beforehand. In other cases, plants with thorns or spines can cause wounds and allow infections to enter the body through the wound.
- Good composting practices are very important to reduce the bio-hazards in the soil.
- Wear gloves and wash your hands after working with compost.
- Use the compost on ornamental plants such as flowers and trees (non-fruit bearing). They will also appreciate the extra nutrients.
Learn more about proper at-home composting on the Life Slice website in the gardening section.