Monitoring Methods and Devices . Plants get most of their water from capillary water . This is the water retained in soil pores after gravitational water has drained. As water is removed by plants or by evaporation from the soil surface, the films of water remaining around the soil particles become thinner and are held by the soil particles more tightly. Water distribution in a soil at field capacity.
Field capacity represents the upper limit of plant-available water.
When the surface tension becomes high, the plant is unable to take up any of the remaining water and permanent wilting results. Water distribution in a soil at thw wilting point. This water is held tightly in thin films around soil particles and is unavailable to plants. The wilting point represents the lower limit of plant-available water. Plant-available water , PAW, is the volume of water stored in the soil reservoir that can be used by plants.