Guidelines for interpreting soil moisture tensions (centibars) measured with Resistance

Blocks and Tensiometers. Soil Type At Our Location Is Clay Loam

Soil Tension

Loam/Silt Loam

Clay Loam/Clay

 

(centibars)

Depletion of the Plant Available Water (%)

10

Not fully drained

Not fully drained

 

30

0

0

 

50

10

10

 

70

25

20

 

90

35

25

 

110

40

32

 

130

47

38

 

150

52

43

 

170

55

46

 

190

58

49

 

Table adapted from Scheduling Irrigations: When and How Much Water to Apply. Division of Agriculture and Natural Resources Publication 3396. University of California Irrigation Program. University of California, Davis. pp. 106.

 

General rule of thumb for interpretation:

Soil moisture is nearing a critically dry level when soil tension (indicated by the centibar meter reading) reaches a level that corresponds to more than 50 percent depletion of the plant available water at a specific soil depth. The critical soil tension level that corresponds with 50 percent depletion levels will vary depending upon soil type because of different soil porosity characteristics.. For example, a soil tension reading of 35 centibars may indicate that a very sandy soil will approach 50 percent depletion of plant available soil moisture but for a loam/silt loam soil 50 percent depletion may not be approached until tension readings approach 110 to 130 centibars.