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Index : Watering
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- 1. Moisture Meters - Top
- One of the most valuable and lest expensive tools for desert gardeners are moisture meters. At a cost of around $5.00, these battery powered devices are great for determining the moisture level of soils in containers, raised beds, and garden beds of flowers and vegetables. They can be purchased at garden, home supply, and hardware stores.
Moisture meters are very effective in determining the moisture content of any potting or garden soil. The meter’s five inch probe is inserted into the soil and the needle gauge registers the moisture level in a range from bone dry to soaking wet.
For flower and vegetable gardens, watering should be done frequently enough to keep the moisture meter in the ‘moist’ range, with the needle registering mid-way between wet and dry. This is also the case with most potted plants, the exception being cacti and succulents. Their soil should be allowed to dry before watering, with the moisture meter needle registering in the dry range, but not bone dry.
It’s important to use the moisture meter frequently enough to determine the schedule of watering. A moisture reading should be taken at the time of watering and then daily thereafter to determine the speed at which the soil loses moisture. When the needle begins to fall into the dry range of the gage, then it’s time to water again. The time it took between the initial watering and the needles drop into the dry range determines the frequency of watering required. If it took three days, then watering every three days should be often enough to keep the soil evenly moist.
When there’s a change in seasonal temperatures and humidity, the frequency of watering will need to be adjusted. When temperatures begin to drop as we head into autumn, the frequency of watering can be decreased. Again, the moisture meter can be used to determine any adjustments needed in the frequency of watering.
Moisture meters are not as effective when used to determine the moisture levels in desert soils. It’s difficult to push the small probe in and it doesn’t go deep enough to determine the moisture levels for deep-rooted trees and shrubs.
The best way to determine the moisture level and the depth of wetting in desert soils is with a long metal rod, preferably three feet in length. A piece of concrete reinforcing bar, available at home supply stores, is great to use for measuring the depth of wetting. A thick wooden dowel rod with a sharpened end may also be used.
The rod can be pushed down through moist soil, but will stop when dry soil is struck. By using the rod immediately after irrigation, the dept of wetting can be determined. For shrubs the soil should be irrigated to a depth of 2 feet. For trees the depth should be 3 feet. If the soil was not moistened deep enough with irrigation, the length of watering should be increased until the soil has been moistened to the proper depth.
Unlike moisture meters, rod for measuring the of wetting and thus the amount of water to be applied, cannot be used to determine the frequency of irrigation. Most desert landscape plants are relatively drought tolerant and do not need frequent irrigation. Check desert landscape plant reference books to determine the general frequency of irrigation.
Written by John Begeman, College of Agriculture and Life Sciences, the University of Arizona,
520-626-5161.
- Updated: September 17, 2006
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