Re: How can I promote healthy microbes for plants?

Hi Jared,
Really interesting question. First of all, you're right that microbes in soil are very beneficial to plants. This comes about through a number of processes. You're probably familiar with the nitrogen fixers, which live in root nodules of certain plants and extract nitrogen from the air. Microbes also make other nutrients available to plants (eg nitrogen in the form of ammonia, sulphur, potassium) through the decomposition of organic matter in the soil and the release of inorganic compounds.

Now, it's true that tap water is often chlorinated, to varying degrees, to suppress microbes. The question is, is the concentration of chlorine high enough to kill microbes in soil? I would guess that it isn't, for the following reasons:

• First, if tap water is allowed to stand, chlorine will escape from it. In the water supply, water is constantly circulated and sealed in pipes to some degree, so quite low concentrations of chlorine are sufficient. When water is poured onto soil, it's likely that a lot of the chlorine escapes or is absorbed onto soil particles before it can reach the microbes.
• Second, tap water left standing is quite capable of supporting microbial growth. You can demonstrate this easily by placing a grain of rice in some water and leaving it for a week or so. You'll notice a hazy, slimy film appearing around the rice grain, which is a film of bacteria. (This is actually a really good way to isolate interesting bacteria).

As to your second question, yes, a commercial water filter will remove most of the dissolved substances in tap water. Most water filters contains activated charcoal, which absorbs chlorine and other non-ionic soluble compounds. They also contain ion exchange resin, which will remove both negative and positive ions (chloride, sodium etc) from the water, giving a pretty pure end product. Depending on where you live, a water filter can be a good health investment. Of course, depending on the mineral content of your local water, you may also be depriving soil microbes of trace elements by filtering it! But again, the concentrations in the soil are likely to be sufficient, especially if you add a little fertiliser of some kind.

I'm sure there's scope for some interesting experiments here. I expect also you are entitled to ask your local water supplier for a detailed analysis of what's in your drinking water, which might be interesting to know.

Neil Saunders