Suction increases as the soil becomes dry and decreases as water is added to the soil. Tensiometer gauge readings are an index to soil moisture and do not require further interpret- ation for individual soils. Tree roots must exert the same energy to draw water from the soil as is indicated on the tensiometer gauge. Install tensiometers on the southwest side of trees in representative areas of the orchard. Sandy soils should be irrigated sooner than clay-type soils because sandy soils hold less water.
Moisture blocks Moisture blocks also show soil moisture.
Resistance to electrical flow is measured with a portable meter. Dry blocks in dry soil have greater resistance to electrical flow than wet blocks in wet soil. The meters come with charts that show relative dryness in various types of soil and will help you determine when to irrigate. The Watermark construction measures moisture lower than the gypsum type and higher than tensiometers. Your irrigation requirement partly depends on how much water your soil can store for future use.