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Ask a Grower

Ask-a-Grower #86

Why use Reverse Osmosis (RO) water?

What’s in our tap water that can be so bad for plants and people? Parts Per Million (PPM) or Total Dissolved Solids (TDS) are both ways to measure the level of what’s in the water besides water. Water that has a PPM or TDS value above 0 contains unknown contaminants which can be harmful to your garden. These contaminants could include, but aren’t limited to, Chlorine, Chloramines, Fluoride, Volatile Organic Compounds (VOC), Nitrates, Iron, Sulfur, Pesticides, Herbicides, Bacteria as well as high levels of dissolved minerals like Calcium and Magnesium. Water with a high PPM or TDS value (above 100 PPM or TDS) should be filtered with a high quality RO filter to obtain a base of “pure water”.

Imagine that the feed chart of your favorite nutrient line says to bring the nutrient solution to 1200 PPM and you are starting with water that is at 500 PPM? It’s hard to even guess what that 500 PPM is composed of, nonetheless try and adjust for it in the nutrient formula you are trying to perfect.

Below is a list of the most common contaminants found in tap water and the effects they can have on your garden.

Chlorine is a boicide that is put into water to kill bacteria, fungus and micro-organisms. One problem with this is Chlorine is a non discriminate killer and kills the beneficial bacteria plants need to thrive. Any healthy organic garden is Chlorine free and it is necessary to remove Chlorine before using water to brew compost teas which are rich in microbial rich life. Chlorine is converted into a gas in the presence of oxygen and can be removed by aerating the water for 24 hours before use.

Many municipalities employ the use of Chloramine which is a biocide made from combining Chlorine and Ammonia and is much more stable than Chlorine. Chloramine can not be “gassed off” by aerating your water source. Similar to Chlorine, Chloramine is toxic to beneficial microbial life and can only be removed by proper filtration.

Fluoride is a hazardous waste product and is added to water by most water municipalities. Fluoride is toxic to plants as well as people. It is know to effect plant enzymes as well seed germination. Enzyme additives won’t work properly if Fluoride is present in the water.

Some Volatile Organic Compounds (VOC) are known carcinogens and can only be removed by proper filtration. Trace amounts of VOC’s can end up in the plants tissue, flower and fruit.

Nitrates end up in the water from agricultural and animal yard runoff. Nitrates are toxic substances that contribute to over-nitrification and algae growth.

Pesticides and Herbicides end up in the water when local agriculture areas use these products providing the possibility of leaching pesticide and herbicides into ground water. These can end up in your water supply and in your plants.

Bacteria can enter the water supply in areas where animal or human waste comes into contact with the water source.

Mineral hardness results from high levels of dissolved calcium and magnesium that can forms scale on equipment and tubing. Too much of either of these in your water and you are locking out key nutrients to your plants. Your plants will be unable to feed properly and will exhibit deficiencies. Mineral hardness is the key cause of water problems in hydroponics and other gardening systems.

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