Learn about upstream conditions that might impact water quality so that possible sources of contamination can be identified and removed.
Surface runoff from animal operations entering produce fields can be a source of microbial contamination. Prevent runoff and airborne drift by constructing physical barriers such as ditches, berms, or grassways. Plant trees as a windbreak to stop blowing dust or separate fields by surrounding them with “buffer zones” planted with a ground cover or green mulch crop.
The Ministry of Agriculture and Food Web site conatins this helpful
guide: Use of Earthen Berms for Erosion Control.
Prevent pesticide spray drift from contaminating surface and groundwater. (Follow all label instructions when applying chemicals.)
When using hillside water catchment systems (collecting and storing rainwater or runoff for later use), filter irrigation water to remove possible contamination.
American Rainwater Catchment Systems Association
Guidelines for Rainwater Catchment Systems brochure.
Use potable water for crop protection sprays to reduce the possibility of chemical, biological, or physical contamination. If potable water is not available, use clean water.
Potable water is water that is suitable for drinking; it is not sterile or free of other substances.
Clean water (safe water) is water that does not contain harmful chemical substances or microrganisms in concentrations that cause illness.
Perform water quality tests for microbial contamination (such as for fecal coliform indicators) on a regular basis and keep accurate records.
A water quality test measures general water factors, such as hardness, salinity, and
dissolved matter, as well as the amounts of chemicals and microbial contaminants in a
sample. Each state or local has water testing labs (many located within University
Extension Departments) that provide instructions and analysis for a small fee. The National Water Quality Program Web site can help you obtain information in your area about testing labs and local laws.
Test results are reported based on the EPA's drinking water standards for maximum contaminant levels (MCLs) of chemicals and coliforms (the presence of these kinds of bacteria indicates the water may have been contaminated by fecal matter and may possibly contain other pathogens).
Currently, the United States has not set maximum contaminant level standards for agricultural water. State laws may specify the allowable contaminant levels for irrigation water from various sources, such as surface water or treated wastewater.
Research and information about pathogen survival rates on vegetables
can be found in the FDA Guidance: Analysis and Evaluation of
Preventive Control Measures for the Control and
Reduction/Elimination of Microbial Hazards on Fresh and Fresh-Cut
The levels of sediments, contaminants, and other measurements will vary depending on the season, regional weather, and other conditions, so a log of test results over time will help determine “normal” levels for your area. A suggested schedule for water testing is pre-planting, the middle of the growing season, and during harvest. Keep a record or log of test results to compare seasonal changes and note any unusual occurrences. This will be part of your permanant on-farm audit records. If a problem is suspected, consider sanitizing your system (pipes and valves, etc.) and/or filtering your water before using. Alternatively, find another water source that meets safety requirements.
NMSU Agricultural Department Disinfecting a Domestic Well with Shock Chlorination. (How-to instructions to reduce microbial contaminants in well water irrigation systems).