Is tap water good for your organic garden?

Is tap water good for your organic garden?

If you are on city water supply just like 94% of U.S. population, it is easy to use tap water for just about everything you do in drinking, washing, flushing, and of course watering your garden. Is the city water really good for everything?

First thing first. Let's first understand what city water is for and how it is regulated. Public water supply is regulated by EPA for about 90 contaminants under The National Primary Drinking Water Regulations. The regulation is targeted to make public water supply safe to drink. To achieve that goal, city utilities actually have to put chemicals in the water. To fight water borne bacteria, chlorine is added so that you won't get sick from drinking tap water. And chloramine - haven't heard about it? It is a new type of chlorine used in last 10-15 years to supplement or replace chlorine. Chloramine lasts longer than chlorine, so the disinfection can stay longer in the supply pipes, making sure the water at your tap is still free from disease borne pathogen.

As we can see, tap water is more for drinking. If you use it for gardening, you can end up with both disinfectants in your garden - chlorine and chloramine. When you water your garden, you don't want to kill those beneficial microbes in your soil that you help to build with organic fertilizer. But just like to disease borne pathogen, chlorine and chloramine will kill those microbes. In one study done by Colorado State University, researchers continuously applied highly chlorinated water to soil for 126 days. Only when they stopped two days after, the soil microorganism populations reached pre-treatment levels. Imagine you water your garden every day, there will be no time for the microorganism colony to recover and rebound.

What else can chlorine or chloramine do to your plants. A study by Japanese researchers showed that root browning occurred in lettuce due to the reaction of hypochlorous acid in tap water and ammonia in the nutrient solution. There have been speculation that unlike chlorine which will bound with soil, chloramine will instead carry its stability and eventually bound with root of plants. Many anecdotal evidence shows that growers have recorded stunted growth, diminished yield, 'burning' of roots and browning of leaves.

So how to get rid of chlorine and chloramine from your tap water. A common practice is to let the water sit out for several hours before using it on plants. That would be useful if there is only chlorine in water, which is very unstable, and will evaporate eventually. But chloramine is a different story. Chloramine in tap water comes from chlorine bound with ammonia.  It is stable and thus very difficult to be removed. Regular activated carbon, which is widely used for chlorine removal, does not do a good job in chloramine removal. To remove chloramine, catalytic carbon needs to be used.  Catalytic carbon is activated carbon with a modified carbon surface. It retains conventional carbon's ability to adsorb contaminants but it also possesses greatly enhanced capacity to catalyze, to promote beneficial chemical reactions. It is by catalytic action that chloramine is removed.

Next time when you water your organic garden, think twice about using city water straight from tap.

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