Importance of post-harvest water quality

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Over 60% of quality can be lost post-harvest if flowers are not handled correctly. This is according to a presentation given by Ruth Vaughn, Technical Director at CropNuts, during a training organized by Flower Watch and CropNuts in Naivasha. The training sought to educate farmers on post-harvest technology, post-harvest water quality and its importance. There are various aspects that affect the quality of the plant post-harvest including the source of water used and the quality of the water. The quality of water in a stem affects such things as the speed of rehydration of a flower, its ability to maintain turgidity, blockage of the xylem and infection of diseases. The Kenya Flower Council takes into account three factors in its audit of its farms water sources; the availability, susceptibility to pollution and the frequency of water analysis.

Borehole water for example is of stable quality and has a low bacterial load. This water source however being from the ground may have high fluoride and heavy metals. Farmers using this source of water are required to test it annually. Availability of surface water however, varies seasonally and has a high bacterial load. This requires the farmers to test the water quarterly or more often. Rain water on the other hand is not always available and has low salts and a low pH. The bacterial load in rain water varies and its quality depends on the storage and collection methods used by the farm and it is recommended to be tested quarterly at a minimum.


Total bacterial count (TBC) refers to the number of bacteria in the water
used, High bacterial count means that the bacteria present will move up the xylem and block it. These bacteria feed on the sugars in the stems and breed inside them. This reduces water uptake and vase life and produces plant toxins. Total suspended solids in water refers to the organic materials and matter in water. When waster has high total suspended solids, they block the xylem and affect the turbidity of the cells and promotes bacterial growth.To solve this issue the water should be filtered of flocculated using additives like aluminum sulphate which binds with particles in the water making them heavier and causing them to sink and leave behind clean water.

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Post- harvest water uptake can also be prevented when the plant experiences a high percentage of dehydration. Typically, roses can recover from over 8% dehydration. However, dehydration above 12% leads to irreversible damage. Embolisms, which are air bubbles that form in the xylem that prevents water uptake to the plant. These air bubbles can be prevented by using cold water because it carries more air which enables it to dissolve the air bubbles it meets in the xylem and help in water uptake. However, since cooling of water in the cold store uses a lot of electricity and the water will not remain cold until it gets to the field, farmers are advised to keep it as cool as possible.

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