WCFS - Western Center for Food Safety

Agricultural Water and Soil Amendments


The Western Center for Food Safety was asked by the U.S. Food and Drug Administration to facilitate the development of research protocols for scientific studies that evaluate the persistence of foodborne pathogens in the environment and on the edible portions of fresh produce following:

  • application of potentially contaminated untreated soil amendments of animal origin to land used to grow fresh produce or
  • application of potentially contaminated agricultural water applied to the edible portion of the crop

Methods used to generate currently available data vary widely and thereby complicate objective evaluation and comparison of data from multiple studies. Two committees of research scientists were established to survey key existing studies and generate recommendations based on their findings. The resulting documents provide a framework for the design of future studies and may be a useful tool for evaluating the strength of existing data.

The Produce Safety Rule (PSR) requires growers to initially establish a Microbial Water Quality Profile (MWQP) for each untreated surface agricultural water source and conduct annual surveys for that water source in subsequent years. The water quality profile is based on the levels of generic E. coli in your agricultural water.

The initial MWQP must be established with a minimum of 20 water samples collected as close to harvest as possible over a period of at least 2 to a maximum of 4 years. Geometric mean (GM) and Statistical Threshold Value (STV) are calculated from these 20 samples (minimum). The GM and STV are your MWQP and should be compared to the microbial quality criteria provided in the Produce Safety Rule.

These tools were developed to make it easy to calculate the GM and STV and to determine if your water meets the standards for unrestricted application to produce before harvest. The tools were also designed to assist you with making food safety management decisions if your water does not meet the standards in the proposed rule.

More information on the Produce Safety Rule and agricultural water can be found here: www.fda.gov/Food/GuidanceRegulation/FSMA/ucm334114.htm 

Quality control of wastewater for irrigated crop production (FAO, United Nations)

Here are three tools:

Framework Documents

The Agricultural Water and Soil Amendment framework documents were developed by two committees through a series of webinars, e-mail communication and a workshop that was held in Davis, CA in October 2011. Additional academic, government and industry food safety experts reviewed the draft documents prior to submission to the Journal of Food Protection.

Related Documents and Resources

Links to information about climate, state-specific resources for agricultural water and manure use on fresh produce, testing methods and related references are found on the Agricultural Water and Soil Amendments pages.