The Poop on Manure


One of the tenets of organic agriculture is to encourage fertility of soil through soil-building practices, including, but not limited to, crop rotation, mulching, and amending the soil with compost and manure. These practices are an attempt to emulate the cycles of growth and decay that build top-soil in nature. In organic agriculture, inputs are sourced from naturally occurring materials, whereas conventional agriculture utilizes synthetic inputs to foster fertility. It is recognized that the primary macronutrients vital to crop production are nitrogen, phosphorus and potassium, or N, P and K, respectively. “Manure is one of the best sources of nitrogen on an organic farm,” (Hansen 2010) and can be applied to production plots either fresh or composted in order to build nitrogen levels in the soil for the growing season. Application of animal manure as a means to build soil fertility is a method that has been practiced since the dawn of agriculture, and performed by both conventional and organic farming operations, although it is more prevalent in organic farming. Animal manure often contains bacteria that can be harmful and even lethal to human beings, and these can be transmitted to agricultural goods if managed or applied improperly. That said, there are many ways to manage the use of animal manure application on the farm that will greatly reduce and even eliminate the risks of bacterial contamination.

Reporter Dennis T. Avery, the director of the Center for Global Food Issues at the Hudson Institute, an American conservative think-tank based in Washington D.C., is a known long-time supporter of industrial agriculture and critic of organic agriculture, and has asserted that, “without the false idea that organic food is safer for people, parents might worry about their children’s food being fertilized with pathogen-laden animal manure.” Avery has made unbacked claims that the CDC has performed studies to determine the risk of bacterial contamination, specifically that of E. Coli, on both organic and conventional produce, and found that organic foods were eight times more likely to be contaminated. Avery demonizes the “scare-tactics” utilized by proponents of organic agriculture through the use of scare-tactics of his own. It must be noted that the Hudson Institute receives funding from conventional food companies as well as chemical companies associated with industrial agriculture, such as Monsanto, ConAgra, and DuPont, and they have often been criticized for their biased stance against organic agriculture. As with any topic of discussion, both sides of the argument must be scrutinized in order to derive an objective conclusion.

Many research studies have been performed to ascertain the viability and longevity of pathogens in manure application and various management systems for composting manure, such as the study by Caihong Song et al. in which it was determined that co-composting different types of animal manures “reduced the quantity of human pathogens” (Song et al. 2014). Another study comparing the viability and transmissibility of E. Coli O157-H7 and Salmonella Typhimurium in soils amended with cattle slurry and human urine found that “the risk of disease transmission is higher when cattle slurry is used as fertiliser compared with human urine,” but, in both instances, “the risk of groundwater infiltration would be low as long as water velocity through the soil is moderate”  (Nyberg et al. 2014). These studies would indicate that as long as proper management techniques are applied, the risks of contamination can be greatly reduced, if not eliminated altogether.

The NOP Final Rule has clear stipulations as to how and when manure can be input into the soil, as well as guidelines for composting and post-harvest handling of produce, in order to mitigate the chance of potentially harmful bacterial contamination. While strict management procedures can be instituted and the utmost of care taken in order to avoid contamination, it still occurs. This may be due in part to the many links that can be involved in the chain of getting the produce from the field to the dinner table. Processing facilities can have a contaminated product pass through their doors, and if proper methods are not utilized or through some form of negligence, product following the contaminated products could be cross-contaminated, causing an outbreak of illness. When this happens and is documented by the media, a whole lot of finger pointing occurs, but the source is eventually determined by retracing the contaminated product back to the processor or producer.

Humanity may never be able to eliminate all things harmful or hazardous, nor do I think it should strive to do so. The bacteria that can be deadly to us are essential in other systems and processes, some of which we have no inkling of an understanding. Animals will always defecate, it’s only natural, and the use of their manure can be a beneficial tool in building soil fertility and productivity if utilized in a safe and effective manner. When using animal manure as an implement in crop production, every precaution (and then some) outlined in the NOP Final Rule should be applied to ensure the safety of the consumer. If the use of manure is banned at any point, what will we then do with all the poop?



Avery, D.T. 2000. An ABC Reporter Riles The Organic Movement [Online]. Available at Accessed 20 Sep. 2014. 

Harken, A.L. 2010. The Organic Farming Manual: A Comprehensive Guide to Starting and Running a Certified Organic Farm. Storey Publishing, North Adams, MA.


Nyberg, K.A., J.R. Ottoson, B. Vinneras, and A. Albihn. 2014. Fate and survival of Salmonella Typhimurium and Escherichia coli O157:H7 in repacked soil lysimeters after application of cattle slurry and human urine. Journal of the Science of Food and Agriculture. 94(12):2541-2546.


Song, C.H., et al. 2014. Comparison of bacterial community structure and dynamics during the thermophilic composting of different types of solid wastes: anaerobic digestion residue, pig manure and chicken manure. Microbial Biotechnology. 7(5):424-433.



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