Best Practices for Promoting Food Safety in Organic Production: Water Quality
- Be sure that high-quality water is used for all operations where the water comes into contact with the edible portion of the plant.
- As the possibility increases for water to make direct contact with fruit, it becomes easier for water contamination to be transferred. Some growers find it useful to divide farm operations into agricultural and postharvest operations. This helps to divert the highest-quality water to the later stages of food production.
- Be sure irrigation water does not contaminate produce. While no comprehensive microbial standards for agricultural water have been established, state regulations require that reclaimed water used for irrigation does not exceed 2.2 total coliforms per 100 mL. World Health Organization guidelines specify less than 1,000 fecal coliforms per 100 mL of water as acceptable. We recommend that these limits be used as guides until more definitive data is available.
- Contact between irrigation water and edible plant parts should be minimized. This may include favoring drip or furrow irrigation instead of spray irrigation. If overhead irrigation must be used, the grower should use water with less than 2.2 E. coli per 100 mL water. Minimizing contact between plants and water when contact isnÕt necessary acts as a safety barrier to cross-contamination between irrigation water (which is often reclaimed water or surface water) and produce.
- Protect the water source. Factors such as run-off, flooding and animal waste may cause contamina- tion in the water supply. Diversion berms and buffer areas may help protect the water source from contaminants brought in by run- off and flooding. Nearby animal production may pose risks to water quality due to high volumes of animal waste production. Water contamination from animal waste has been shown to be involved in outbreaks of E. coli O157:H7. The use of fences or gates may help keep animals out.
- Maintain and repair wells regularly. This includes having well casings inspected regularly and repaired as needed. Growers who rely on wells for their water source should have wells inspected and their water tested annually by a water quality expert.
- The grower should be aware of his/her certifying agency's guidelines for water disinfectants. Organic operations may not permit the same levels of chlorine for sanitizing irrigation equipment or for water disinfection that conventional growers use. California Certified Organic Farmers allow a maximum of 50 parts per million of chlorine to come into initial contact with edible produce. They also stipulate that the flush water from irrigation equipment may not contain more than 4 parts per mil- lion of chlorine, the maximum for drinking water. Each organic certifying agency has its own guidelines; consult with your agency for specifics.
Written by Shantana Goerge, postgraduate researcher, from materials developed by Trevor Suslow, Extension specialist, Department of Vegetable Crops, UC Davis.