I use manures in my garden. Unfortunately, especially in the United States, there's been a lot of debate about using manures in the organic garden. Organic certification there requires:
Certified organic farmers, however, must have a farm plan detailing the methods used to build soil fertility including the application of manure or composted manure. Certified organic farmers are prohibited from using raw manure for at least 90 days before harvest of crops grown for human consumption....The U.S. regulations for organic production require that raw animal manure must be composted unless it is applied to land used for a crop not intended for human consumption; or is incorporated into the soil not less than 120 days prior to the harvest of a product whose edible portion has direct contact with soil; or is incorporated into the soil not less than 90 days prior to the harvest of a product whose edible portion does not have direct contact with the soil surface or soil particles.
One reason for this was an engineered backlash that argued that organic produce was food grown in manure...and that it was a health risk to eat. So organic farmers worked hard to cover themselves.
The UK body has a different approach:
Livestock manure can be used with the agreement of your organic CB as a supplement where the fertility building phase of the rotation is not sufficient to produce the required soil nutrient level. Where possible manures, which should normally be composted before use, should be recycled on the farm on which they were produced. If they are taken off the farm they must be used on another organic holding. Organic standards strictly control the use of brought-in animal manures from non-organic holdings - they can only be used with the permission of your organic CB and must come from extensive production systems.
In effect, what organic farmers are being forced to do is source their compost from commercial suppliers, who have a strict scientific approach to composting, rather than invest in the business, and presumed risks, of creating their own. This adds to in farm costs and the price of organic foods.
Jeff Gillman addresses this topic in The Truth About Organic Gardening:
"'The practice of adding compost, including composted manure, to soil is a good one as long as you compost appropriately." Gillman, however, does cite a study that found that E. coli O157:H7 can live in uncomposted manure for 21 months.
Cornell University similarly argues:
Fresh manure must be used with caution in the garden because it may contain pathogenic bacteria such as E. coli, Listeria, and Salmonella. Although the chance of contamination is slim, severe sickness and even death may occur if contaminated produce is eaten. To be safe, either compost your manure or apply it in the fall after harvest. Wash your hands after handling manure and try to leave at least 120 days between application of fresh manure and harvest of a crop.
The complication is really salad veg in contact with any manured soil, as well as unwashed and uncooked root vegetables, which may act as fomites for E.Coli and Salmonella.
I've always presumed anything coming from the dirt to be 'dirty' and should be treated accordingly.
This of course raises the prospect of to Manure Or Not To Manure (discussion thread is excellent). However, further polemics exist that argue that you should not even add animal manures to your domestic compost heap because the quality of your composting process may not be up to the sterilisation standards needed: right temperature/required time span.
However I did find this research snippet:Fate of Escherichia coli O157:H7 in Manure-Amended Soil which reports:
Escherichia coli O157:H7 cells survived for up to 77, >226, and 231 days in manure-amended autoclaved soil held at 5, 15, and 21°C, respectively. Pathogen populations declined more rapidly in manure-amended unautoclaved soil under the same conditions, likely due to antagonistic interactions with indigenous soil microorganisms. E. coli O157:H7 cells were inactivated more rapidly in both autoclaved and unautoclaved soils amended with manure at a ratio of 1 part manure to 10 parts soil at 15 and 21°C than in soil samples containing dilute amounts of manure. The manure-to-soil ratio, soil temperature, and indigenous microorganisms of the soil appear to be contributory factors to the pathogen's survival in manure-amended soil.
Confused? Well the research may not be conclusive and you'll find many variations of recommendations online about how to handle animal manures in the vegetable garden. As you know animal manures are an efficient way to heat up a compost heap ...and do it quickly.
- Useful resource:5 Tips for Using Manures in the Garden
But there may be a way around all this if you think your habits need adjusting. This approach composts animal manures alone rather than mixing them up with other stuff. And you compost very hot and very quickly. This is a variation of the Berkeley method, developed by the University of California, Berkley...but it's less labour intense. I suggest it may also be a good idea to keep a cake or meat thermometer on hand and make sure your pile registers 60 degrees Celsius. I suspect that a variation of this technique was used by the 19th Century French Intensive Market gardeners, although they buried their manures to compost anaerobically.
