These instruments should be placed in strategic locations within the plant root- and wetted zone. Depending on the plant's maximum rooting depth and soil type, more than one tensiometer may be required per site. For example, one might be placed at a depth of 12 inches and another at a depth of 30 inches. These should be located just at the inner edge of the normal wetted area. Tensiometers require frequent supervision and must be correctly installed and serviced in order to obtain reliable results.
Some growers feel that graphing daily readings is a good way to track moisture status.
Generally, for optimum results the tensiometers should read in the 10 to 30 centibar range. Electrical resistance blocks . These instruments measure available soil moisture percentage. A calibration curve is required to determine the soil moisture percentage based on soil type and ohm resistance. Electrical resistance blocks should be installed at locations similar to those discussed for tensiometers.