Water Quality Considerations for Produce Farmers

Best Practices for Irrigation

Every farm’s produce safety plan should include a description of the water system. This description can use maps, photographs, drawings, or other means to communicate the location of permanent fixtures and water flow through the system (including any water being captured for use). Permanent fixtures include wells, gates, ponds, valves, returns, and other above-ground features that make up the complete irrigation system. The direction of water flow should be indicated on each map. If feasible, underground piping or conveyances should be included on maps.

Use a trickle-water system whenever possible. This strategy minimizes any potential hazards or contamination of produce, since the consumable parts of most crops are not wet directly. Drip irrigation may also decrease plant disease levels and maximize water usage.

If surface water is used for overhead water systems, consider the water source and be mindful of upstream uses of that water. Consider not applying overhead irrigation for at least one week before harvest if water draws from a surface water source.

By applying overhead irrigation in the morning, leaf-drying time is extended. In addition, quick-drying of plant foliage and bright light will reduce the survival of both plant and human pathogens on crops.

Test the irrigation water as near to the point-of-use as possible, and if microbial activity levels are above thresholds, take appropriate corrective actions. Keep documentation of all test results or certificates of inspection for at least two years, including records of application strategies, rates and dates.

Heavy downpours or water systems may increase the probability of soil contamination. In particular, lettuce and other leafy greens may come into contact with infected soil when heavy rainfall occurs. Farmers must consider harvest practices such as removing solid leaves or not harvesting soil heads when excessive soil or mud builds on greens.

Care must be taken to decrease the potential for windborne soil, water, or other media to contaminate lettuce and leafy greens.

When waters from different sources are combined, consider the potential for pathogen development within the water. Consider the effect of storms on surface water sources. Bacterial loads in surface water are, for the most part, much higher after a storm and great care must be taken when using this water for irrigation.

Use methods for putting away irrigation equipment that prevents the potential for pest invasion. Create strategies to supply microbial-safe irrigation pipes and drip tape if a pest infestation occurs.

Checklist to Prevent Produce Contamination

Test irrigation water and water used in harvest operations to assure that it meets quality standards (microbial, chemical, physical) for its intended use. When combining water from various sources, consider the potential for pathogen growth. Treat water, if necessary, before using it to irrigate crops or to wash harvested products.

Evaluate irrigation methods (drip irrigation, overhead sprinkler, furrow) for their potential to introduce, support or promote the growth of pathogens on fruits and vegetables.

Evaluate irrigation water storage conditions and devise effective strategies for reducing, controlling, or eliminating potential contamination.

Use procedures for storing irrigation pipes and drip tape that reduce potential pest infestations. Develop processes to assure safe use of irrigation pipes and drip tape if a pest infestation does occur.

Ensure the water used in direct or indirect application on edible portions of crops has appropriate microbial quality. Water may be tested regularly, treated or drawn from a proper source to ensure it is appropriate for its intended purpose.

Water used during harvesting must meet U.S. EPA 1986 microbial standards for drinking water and should be tested periodically to ensure that it is of appropriate microbial quality.

References

• Effect of the food production chain from farm practices to vegetable processing on outbreak incidence Yangjin Jung, Hyein Jang, and Karl R. Matthews, Department of Food Science, Rutgers, The State University of New Jersey, New Brunswick, NJ 08901, USA.
• CDC (2007) Irrigation water issues potentially related to 2006 E. coli 0157:H7 in spinach outbreak. URL https://www.cdc.gov/nceh/ehs/docs/investigation_of_an_e_coli_outbreak_associated_with_dole_pre-packaged_spinach.pdf. Accessed September 2014.
• CDC (2008) Outbreak of Salmonella serotype Saint Paul infections associated with multiple raw produce items. MMWR Morb Mortal Wkly Rep 57: 929–934.