Measuring Soil Moisture
Soil moisture tension is a negative pressure. When more pressure (energy) is needed for the plant to extract water from the soil, the value is represented by an increasing number. Saturated soil has a soil tension of about 0.001 bars, while soils around plants in the desert are roughly around 60 bars. Field capacity, which is used in agricultural practices is about 0.33 bars.
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Some guidelines for soil moisture measurements are:
- 0-10 Centibars = Saturated soil
- 10-30 Centibars = Soil is adequately wet (except coarse sands, which are beginning to lose water)
- 30-60 Centibars = Usual range for irrigation (most soils)
- 60-100 Centibars = Usual range for irrigation in heavy clay
- 100-200 Centibars = Soil is becoming dangerously dry for maximum production. Proceed with caution!