Chlorine can kill beneficial microorganisms in soil, thereby affecting plant growth; however, most chlorinated drinking water is not concentrated enough to adversely affect plant life in a given area. This is due to the fact that the reproduction rate of microorganisms in the soil is so high that they tend to reproduce again before the plant can be negatively affect by the soil.
Most communities add small amounts of chlorine to drinking water to ensure safety for residents. Typical drinking water does not contain high enough amounts of chlorine to truly eliminate beneficial microorganisms in the soil, thereby minimally affecting plant growth. Beneficial microorganisms found in soil reproduce at such high rates, making the effects of chlorinated water nearly moot.
Chlorine also binds to the surfaces of soil particles, which reduces the chlorine's ability to destroy beneficial microorganisms. In addition, as chlorinated water trickles down to lower levels of soil, the chlorine binds to the surfaces of those soil particles, meaning that the water contains less chlorine as it moves down. Studies show that soil subjected to chlorinated drinking water only displayed a reduction in microorganisms in the upper 1/2 inch of soil. Microorganisms in soil levels deeper than 1 inch were unaffected by the chlorine.