Irrigation water testing

Irrigation water quantity and quality is a big deal for many growers.  The American West is the setting for the water wars described in Cadillac Desert, Marc Reisner’s epic story of political corruption and greed brought on by a limited resource in a desert landscape. While not directly pertaining to water quality, the book points to the importance of water. We can’t grow without it.  Water is an integral part of the garden farm.

There can be a surprising amount of minerals in irrigation water.  In fact, some irrigation water may supply, for example, all the calcium plants need to make a crop, along with a host of other helpful and detrimental minerals.  Even municipal water supplies may be adding minerals and will almost certainly be adding chlorine and possibly chloramine.  An irrigation water test can help to sort out what is coming in with your irrigation water.

We would not expect well water to change much with time so a single test may be all that is needed.  The same may be true for water that comes from a reservoir filled annually by snow melt or winter rains.  However some water may change with the seasons, for example municipal water may change its mix as the summer progresses.

Minerals in irrigation water can build up in the soil and harm plants.  We often see this in container plants such as house plants which form a white crust on the soil surface from built up minerals. Mineral buildup requires periodic leaching, i.e. watering enough at one time to dissolve the excess minerals and flush them out of the root zone. A water test can alert you to the potential for mineral build up and the need to leach periodically.

Logan Labs offers a standard water test as well as an irrigation suitability test with additional test items.  You may order the test directly from them.  A 16 ounce (one pint / 1/2 liter) bottle of water can do 3 saturated paste tests plus the water test. Since you will be shipping the water bottle, choose a plastic bottle.  Using a clean bottle to start with, rinse three times with the irrigation water, then fill it.

Once you have your test results, we have a guide to help you interpret them.