Wires from the electrodes attach to a meter that measures electrical conductivity, a function of the water content of the soil. To install moisture blocks, dig a hole with a soil auger and place the block in it. Pack soil around the block to ensure good capillary action between the sensor and the soil. Calibrate blocks in each field to ensure accurate prediction. Moisture blocks are not recommended for sandy soils.
Tensiometers are well adapted to sandier soils.
This is directly related to the tension required for plant roots to extract water from the soil. Tensiometers consist of a tube with a porous ceramic cup at one end and a gauge at the other. To install, place in the soil to the depth of plant rooting. Fill with water. As the soil dries, the tension increases, indicating water is more difficult to extract from the soil.