Summary of Awards to Date

Establishment of vegetative buffer zones to reduce the risk of STEC and Salmonella transmission from animal operations to fresh produce on co-managed farms.


Jan. 1, 2018 - Dec. 31, 2019

Funding Agency

Center for Produce Safety

Amount Awarded



Siddhartha Thakur, Ph.D.
North Carolina State University


Eduardo Gutierrez, Ph.D., Chris Gunter, Ph.D.


To provide fresh, healthy and safe produce to consumers, we need to find effective and efficient practices that will allow us to continue farming with limited resources and land availability. Sustainable farming practices have, at their core, an integration of crops and livestock, recycling of nutrients and the well-being of humans and the environment. These farming practices increase crop productivity and environmental stewardship, though knowledge gaps exist specific to the presence and/or removal of a vegetative buffer zone (VBZ) between animal production areas (APA) and produce fields and the potential relationship for pathogen transfer. This proposal will evaluate the effectiveness in reducing or eliminating movement of Shiga toxin-producing Escherichia coli (STEC) and Salmonella from APAs to adjacent produce fields by establishing a fast-growing and cost-effective VBZ between these areas within a 1–2 year growing season. Our proposal is unique and based on data collected from previous CPS- and USDA-funded projects. Our proposed study will: 1- determine the risks associated with the presence of VBZ as barriers and/or sources of pathogen transmission between APA and produce fields, 2- determine whether pathogen movement into produce fields increases with removal of VBZ, and 3- determine if the proposed strategy is a tangible solution for growers facing these co-management practices.

Technical Abstract

Co-managing livestock and fresh produce continues to be linked to high-risk potential for pathogen transmission and contamination while land and water resources continue to dwindle in many of our fruit and vegetable production areas. The experimental and rational framework of this proposal is based on two previously completed research projects in which we targeted: 1- Movement of pathogens from animal production areas (APAs) to produce fields within 30–400 ft buffer zone distances (CPS funded) and, 2- Bio-mitigation practices to reduce the persistence of human pathogens in soil (USDA funded). Further, we have initiated the establishment of two vegetative areas in between dairy and poultry operations in the research station, where the proposed study will be conducted, that will be at the desired height once we initiate this project. In our recently completed 2-year study funded by CPS, we clearly showed the transmission of STEC and Salmonella from livestock to fresh produce in sustainable farms where animals are by design in close proximity to fresh produce. Our results indicate that a) the Leafy Green Marketing Agreement (LGMA) suggested buffer zone distance of 400 ft between APAs and the edge of a crop, and b) the 30-ft buffer zone for grazing lands or domestic animals and the edge of the crop, may not be appropriate. Consequently, further studies are needed to revise this distance and to identify functional and cost-effective barriers that can reduce pathogen transfer into produce without negatively impacting land availability and wildlife habitat. Additionally, many farmers are in the process of complying with the FSMA produce rule and as part of their risk analysis and potential corrective actions, they will need to implement practices that can reduce the risk of pathogen transfer and contamination from APAs to adjacent produce fields. Currently there are little to no alternatives to reduce this transfer besides moving the produce fields to another location. Results from our USDA-funded project suggest that the use of solarization in combination with mustard cover cropping and compost can significantly reduce the persistence of Salmonella and STEC in soil. By combining the successful completion of previous research and new preliminary information, we propose to follow a hurdle approach to address two of the most important and elusive questions around co-management: 1- What is the risk associated with proximity of vegetative areas as a potential source of human pathogen contamination to fresh produce?, and 2- Can these areas actually serve as barriers for pathogen transmission to produce, even in the presence of APAs? These two questions are key to the sustainability of many different farming practices across the globe and specifically in the southeastern United States, where small to medium-size animal producers, vegetative or riparian areas, and woodlands are in close proximity to produce fields.