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TNAU Agritech Portal :: Good Agricultural Practices (GAP)

Good Agricultural Practices for the Production of Leafy Greens

Principles and practices that will help minimize contamination, reduce survival of pathogens and prevent cross-contamination.

Know where the risks are:


Like all crops, leafy greens require water either via rain events or through irrigation. If it's time to irrigate, know the quality of your water source. Growers pull water from ponds, rivers, streams, canals, and ditches. The risk of contamination upstream, especially when pulling from rivers, streams, canals and ditches must be considered. Regardless of the irrigation source, test your water regularly. This will provide a snapshot of water quality at the time of testing and will allow growers to document changes over time. It may also pinpoint periods during the growing season when water quality may be suspect.
Evaluate the irrigation method. For instance, trickle irrigation can reduce the risk of contamination because there is minimal contact with the edible portion of the plant. Compare this to overhead irrigation, where most water contact occurs on the foliage.
In addition, one important agricultural practice is to protect and maintain safe irrigation water sources. For example, maintenance of wells and ponds and the prevention of polluted run-off from entering water sources will help to reduce the risk of contamination.


 All horticultural crops require nitrogen and other nutrients to grow. Growers can provide nitrogen to their crops through synthetic fertilizers, manure or manure-based composts. If manure or manure-based composts are used, growers must recognize the risk of contamination. Manure and improperly managed compost may act as a reservoir for pathogenic bacteria like E.coli. Good agricultural practices require that untreated or partially treated manure not be used in leafy greens production because the interval between application, planting and harvest, is not long enough to reduce the risk of contamination (you need approximately 120 days between nutrient application and harvest). If you want to use manure as a source of nutrients, apply to the field after final harvest to maximize the interval. Also, if purchasing compost, always ask for documentation to ensure a composting process was completed. If you are composting on-farm, keep good records - record the treatment procedure and the date treated.


Worker Sanitation

 Ensure that all staff is educated on the importance and need for good hygiene. Washing of hands is an effective way to minimize worker-based contamination. If running water isn't available, supply workers with water-free hand sanitizers, they only cost a few dollars! And, ensure field workers have access to washroom facilities that are properly maintained and serviced.

Harvest and Packing

Many leafy greens are harvested and packed in the field. However, some do receive further processing including washing and individual packaging. It is important that all equipment that comes in contact with leafy greens, whether in the field or packing shed, is cleaned on a regular basis. Knives, containers, and baskets should be sanitized between uses. All processing water should be sampled on a regular basis. If your operation uses re-circulated water, ensure that practices are in place to reduce the risk of contamination through the use of sanitizers, or frequent changes of water.


Unfortunately, the risk of contamination doesn't end when the produce leaves the grower's premises. The risk of microbial pathogens and reduced quality can increase during transportation if proper temperatures are not maintained. In fact, temperature abuse anywhere along the food-chain can turn a small problem into a large problem due to rapid growth of bacteria. Another important factor to consider is vehicle cleanliness. Always inspect trucks for cleanliness, odours and obvious dirt before loading.


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