Agriculture Reference
In-Depth Information
8
The Role of Manure and Compost in
Produce Safety
Xiuping Jiang and Marion Shepherd
Introduction
Fresh fruits and vegetables are vital components of a healthy and balanced diet. Most
fruits and vegetables are considered as ready-to-eat (RTE) food with minimal or no
terminal treatments before consumption. However, foodborne disease outbreaks in
recent years have been increasingly associated with the consumption of fresh produce
in the United States. The majority of these outbreaks were due to pathogens trans-
mitted via fecal-oral routes (Johnston and others 2006).
Animal wastes are an important source of nutrients for crop production, but may
contain a variety of human pathogens such as
Esherichia coli
O157:H7,
Salmonella
spp., and
Listeria monocytogenes
(Pell 1997). In the past, concerns over animal
manure were focused primarily on the nutrient's effect on the environment and the
ineffi cient use in agricultural systems, with little effort on characterizing the fate and
reduction of pathogens (Sobsey and others 2001). In addition to the contaminated
irrigation or runoff waters, raw or improperly composted manure used as organic
fertilizer and soil amendments have been identifi ed as potential vehicles for contami-
nation of vegetables during preharvest (FDA 2001; Buck and others 2003). Numerous
cases of foodborne illnesses have been associated with the consumption of fresh
vegetables in part contaminated by manure from ruminants and poultry (Schlech and
others 1983; Morgan and others 1988; Cieslak and others 1993; CDC 1996, 2007).
Recently, several large produce-related outbreaks of
E. coli
O157:H7 and
Salmonella
spp. have led to major concerns about the contamination of vegetables with fecal
pathogenic bacteria in the agricultural environment (CDC 2006; Doyle and Erickson
2008 ).
Land spreading of animal manure can lead to the introduction of enteric pathogens
into the food chain. Foodborne pathogens such as
E. coli
O157:H7,
Salmonella
, and
L. monocytogenes
can survive in soil for several months following the manure applica-
tion (Kudva and others 1998; Fenlon 2000; Jiang and others 2002, 2004; Natvig and
others 2002), and contaminate the vegetables grown in the soil fertilized with manure
(Ingham and others 2004, 2005; Islam and others 2004a-d, 2005). Therefore, control-
ling pathogen populations in the animal wastes used for agricultural production should
help in reducing pathogen contamination of the preharvest environment.
Due to the large production of animal manure by animal production systems, how
to dispose of these wastes safely can be a very challenging task (US SAC 1998).
Composting is used by farmers to treat various types of animal waste, and the compost
can then be utilized as the value-added fertilizer and soil amendment. Composting as
a practical way for pathogen inactivation is largely due to a self-heating process carried
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