Permanent wilting point. For example, one cubic meter of soil with 30% VWC contains 0.3 cubic meter, or 300 liters, of water. This is illustrated in Fig. Fig. It is at the lower end of the available moisture range. Soil at permanent wilting point is not dry. Volumetric Water Content (“VWC”) is a numerical measure of soil moisture. The amount of water actually available to the plant is the amount of water stored in the soil at field capacity minus the water that will remain in the soil at permanent wilting point. It’s the soil potential at which sunflowers wilt and are unable to recover overnight. permanent wilting point is the water content of the soil at -1.5 MPa water potential. VWC at this point can range from 5% to 40%. Soil at the Permanent Wilting Point is not completely dry, as it still has a little bit of water; but the amount is so little it is not accessible by plants. Fig. When the water content of a soil is below the permanent wilting point, water is still be present in the soil, but plants are unable to access it. As soil is subject to evaporation and withdrawals from plants, water content decreases and tension increases to a point where plants can no longer extract water. Maintaining soil at this level for any length of time can cause permanent damage to plants. Thus, the -15 atm moisture content provides a reasonable estimate of the wilting point. It’s theoretically the empty tank, where there is a complete loss of turgor pressure, and the plant has wilted. If the plant does not get sufficient water to meet its needs, it will wilt permanently. Permanent Wilting Point Permanent wilting point or the wilting coefficient is that water content at which plants can no longer extract sufficient water from the soil for its growth. permanent wilting point is determined as the soil moisture content at which the plant is no longer able to absorb water from the soil causing the plant to wilt and die if additional water is not provided. Then it comes to the point that the plant can no longer extract water from the soil (Permanent Wilting Point). It is expressed as a percentage or ratio of the amount of water held by the soil. Permanent Wilting Point. Any moisture content below this level is in the 'Stress' zones. You should expect VWC readings between 5% and 35% depending on your soil type. At PWP, soil particles hold the water so strongly that it becomes difficult for plant roots to extract it. Permanent wilting point was experimentally determined in sunflowers and defined as -15 bars (-1500 kPa, Briggs and Shantz, 1912, p. 9). 39. 38c. Generally, at the permanent wilting point the soil moisture coefficient is defined as the moisture content corresponding to a pressure of -15 atmospheres from a pressure plate test. . The available soil moisture or water content Permanent wilting point (PWP) is the threshold where it becomes impossible for plants to extract water at a rate fast enough to keep up with their water demand. Although actual wilting points can be somewhere between -10 and -20 atm, the soil moisture content varies little in this range. 39.