Organic Vegetable Production in Alabama

With the recent outbreak of E. coli in spinach and lettuce and the ensuing questions of whether organic practices of using manure as fertilizer contributed to the outbreak, we felt that a review of composting practices would be helpful. At this time no evidence was found that organic products were involved in the outbreak. However, some concern among the public exists. To respond to concerns growers and consumers may have, we have reviewed standards on for composting and research on E. coli outbreaks.

First, let’s look at what the Nation Organic Programs standards and regulations say about composting and soil nutrient management. The soil fertility and crop nutrient management practice standard (§ 205.203) of the National Organic Program can be accessed online at

http://www.ams.usda.gov/nop/NOP/standards/FullRegTextOnly.html.

However, a summary follows.

APPLYING MANURE DIRECTLY

NOP standards state that the producer must manage crop nutrients and soil fertility in such a way as to prevent the contamination of crops, soil, or water by pathogenic organisms. Raw manure must be composted unless it is applied to land used for a crop not intended for human consumption.

In the event that composting is not possible (do try your best to compost), the manure must be incorporated into the soil at least 120 days before the harvest of a product whose edible portion has direct contact with the soil surface or soil particles. In the case of a crop whose edible portion does not have direct contact with the soil surface or soil particles, the manure must be applied a least 90 days prior to the harvest of the crop.

Arnold Caylor turns compost pile at Cullman

Remember: Use of sewage sludge is prohibited in organic crop production.

Compost plant and animal materials through a process that establishes an initial C:N ratio (carbon to nitrogen) of between 25:1 and 40:1. If you are using an in-veesel or static aerated pile system, then maintain the temperature of the compost between 131 F and 170 F for 3 days. When using a windrow composting sytem, make sure that the temperature stays between 131 F and 170 F for 15 day. During this time, the materials must be turned a minimum of five times.

A REVIEW OF THE LITERATURE

The Organic Center (http://www.organic-center.org) has published a very thorough review-- http://www.organic-center.org/reportfiles/e_coli_final.pdf --of the recent scientific research on pathways of E. coli contamination in food supplies. Some may argue that the center has a bias. Perhaps. But, the site and articles contain numerous references to peer reviewed journal articles. Use these articles as your springboard into your own research. Read critically, ask the hard questions, and let us know your thoughts about a particular article The link to the bibliography is http://www.organic- center.org/reportfiles/E.Coli_Epi_Reference_Manager.pdf

If research isn't in your schedule, look through the above references and the following quotes, which are taken directly from the Organic Center's review article.

“The NOP requirements, and other practices followed by organic farmers to prevent E. coli O157 contamination, are not infallible, nor are the practices used by conventional farmers, who are bound by no government food-safety driven restrictions on when and how animal manures can be applied. Most scientists who have studied the impacts of manure management, composting systems, and manure and compost application methods on E. coli survival in the soil and on crops agree that further research is needed to assure adequate margins of food safety.

"The results of most published research supports the conclusion that under normal conditions, properly managed and applied manure and compost, on organic and conventional farms, does not pose a food safety threat. But published research also shows clearly that margins of safety are not great enough to eliminate risk under combinations of unusual conditions that might include odd weather, unusual pest problems, operator error, equipment failures, lack of effort in sanitizing equipment, or lack of knowledge.”

So, err on the safe side. Get that manure in a compost pile or windrow and start turning this fall. Keep records of the internal temperature. It should be safe to use in time for spring planting.

If you would like to know where E. coli outbreaks come from keep reading.

WHERE DOES E. coli COME FROM?

The vast majority of E. coli 0157 bacteria start out in the digestive systems of beef and dairy cattle (Valcour et al., 2002; Cidrap, 2006) What can a farmer do to reduce E. coli levels in their animals? Gilbert et al. (2005) found that enterohaemorrhagic E. coli (EHEC) levels were 100-times higher in cattle fed a high grain ration, compared to animals on a roughage-based diet. A high grain diet changes the pH of the cow's intestine to favor E. coli.