Efficiently watering fields and landscapes is the most effective method of overall water conservation. How much water to add through irrigation depends on current weather conditions, the type of plants and their level of development.
A term used to describe the water consumed by plants over a period of time (transpiration) and taking into consideration weather conditions (evaporation), is called evapotranspiration, or ET.
Local weather conditions are important because ET is driven by weather factors that determine the drying power of the air. We can accurately predict ET losses in a given area from the measurement of four local weather variables: solar radiation, temperature, humidity and wind.
Efficient irrigation requires knowing:
1. The amount of water lost through evapotranspiration (the ET rate).
2. The amount of rainfall received since the last irrigation.
3. The amount of soil moisture.
The Natural Resources Conservation Service (NRCS) has recently begun measuring ET using an atmometer, which basically acts as a mini weather station that will provide ET data.
In addition, it is also measuring current rainfall amounts and this information will be published weekly in this article.
Finally, the NRCS can also provide a brochure so that individuals can easily measure their soil moisture by simply digging to root zone depth and using visual comparisons to estimate current soil moisture. These three variables can then be used for irrigation scheduling.