MICROBIAL ECOLOGY AND SAFETY OF FRESH ON-FARM ORGANICALLY GROWN PRODUCE
Title: Manure Management
Submitted to: Complete Book
Publication Type: Book / Chapter
Publication Acceptance Date: October 31, 2008
Publication Date: July 14, 2009
Citation: Millner, P.D. 2009. Manure Management. In: Sapers, G., Solomon, E. Matthews, K., editors. The Produce Contamination Problem--Causes and Solutions. Burlington, MA: Elsevier Press. p. 79-104.
Interpretive Summary: Foodborne illness outbreaks associated with consumption of fresh fruits and vegetables have increased concerns about contamination of produce from fugitive enteric pathogens at the primary field production level. Possible contamination sources of concern at the field production stage can include environmental, equipment and inputs, and employee sources. In the environmental and input categories major concerns include wildlife and domestic farm animals, runoff from pasture and rangeland grazing, and feeding and-or loafing lots, contaminated surface water, and manure-based soil amendments. The complexity and large areas of agricultural production landscapes have presented considerable challenges for the production industry and food safety and public health authorities to pinpoint the exact sources and pathways of pathogen contamination at the field level in many cases. Treating manure to eliminate pathogens prior to intentional use in fresh fruit and vegetable production systems is one of several food safety crop protection strategies available. Recent advances in manure treatment technologies include pathogen destruction as an integral and critical objective of treatment processes along with nutrient stabilization and air emissions management. This report provides current information on what is known about the survival of E. coli O157:H7, Salmonella spp., Listeria monocytogenes, Campylobacter spp., parasites, and viruses in animal manure in various traditional management systems, such as mesophilic digestors, high stacks, and conventional lagoons. In contrast to the relatively low level of environmental controls available in these traditional manure management systems and consequent low predictability of pathogen survival, contemporary thermophilic and multi-stage treatment technologies, based on aerobic or anaerobic digestion of liquids and managed composting of solids, or multi-stage constructed wetlands are particularly effective in destroying pathogens when operated properly. Management of manure runoff from feed and loafing lots, grazing and rangelands is particularly challenging because of the potential for landscape scale dispersal and subsequent survival of pathogens, even if at trace concentrations. Field-scale data on vegetated filter areas receiving manure runoff show progress in identifying strategic use of beneficial management practices for reducing manure pathogen movement from deposition areas in grazing or feedlot situations. In other studies, data show that survival of enteric pathogens is similar for organic and conventional production systems and thus both can benefit from implementing Good Agricultural Practices at the primary field production stage, particularly with regard to use of adequately treated manure and manure-based products. Use of manure that is intentionally managed using treatment technologies (not just aged) to reduce even very durable pathogens such as helminth (worm) ova is preferred, and in some crop marketing sectors required, over use of raw manure. The value of a HACCP-based strategy for producing compost from manure and other potentially pathogen-laden materials (such as cafeteria and food processing residuals) is discussed in the context of its intended use in fresh fruit and vegetable cropping systems. This report will be useful to growers, packers and fresh-cut processors, and their trade associations and suppliers, especially those organizations impacted by recent outbreaks of foodborne illness. Researchers investigating ways to avoid contamination and improve the microbiological safety of fresh produce will find this information valuable.
Understanding of manure management methods and practices from the perspective of pathogen prevalence, survival, and susceptibility to various treatment effects has led to development of several beneficial management practices and technologies for reducing manure pathogens in agricultural landscapes. This chapter presents examples of current data on the prevalence and survival of E. coli O157:H7, Salmonella spp., Listeria monocytogenes, Campylobacter spp., parasites, and viruses in animal manure in various traditional management systems. Consistent disinfection of all groups of pathogens by traditional storage systems, such as conventional lagoons, mesophilic digestors, and high stacks, cannot be reliably predicted, because these systems do not provide sufficient control of the environmental factors critical to microbial destruction. Advanced manure treatment technologies specifically target reliable and consistent pathogen destruction, in addition to nutrient stabilization and reduction of volatile organic compound emissions, by design. Thermophilic and multi-stage treatment technologies, based on aerobic or anaerobic digestion and/or composting, are particularly effective in destroying very resistant pathogens when operated properly. Data and reports about pathogen survival in organic as well as conventional production systems show the need for use of Good Agricultural Practices in both production approaches particularly with regard to use of manure and manure-based soil amendments. Naturalistic and experimental studies involving runoff from feedlots and grazing land provide information about pathogens survival and transport in various types of raw and treated manures. Field-scale data on vegetated filter areas receiving runoff support the development of beneficial management practices for use in reducing manure pathogen movement from deposition areas in grazing or feedlot situations. Use of a HACCP framework is presented and discussed for composting manure and other feedstocks intended for use in primary fresh produce cropping systems.