Soil water potential, water content and its physiological significance

The moisture in the soil can be described in two ways: water content and water potential. Water content refers to the volume of water per unit volume of soil or the weight of water per unit weight of soil. The unit is cm3/cm3%, kg/kg%; the soil water potential is the unit water extracted from the soil under isothermal conditions. The energy required, in bar (bar, 1 bar = 100 kPa), the soil moisture is saturated, the water potential is zero; the water content is lower than the saturated state, the water potential is negative, and the soil is dry, the negative value is larger (measuring the soil moisture) The instrument has a TRS-II soil water potential meter, which can be seen in detail at http://). Typical plants have a range of 0 to -15 bar (-1500 kPa). Water content, water potential, these two indicators are equivalent to the electron density and potential in electricity. Unlike water potential, water content does not reflect the effectiveness of soil moisture on plants. For example, 15% water content is already quite moist in the sand, and almost all plants can grow. If the clay contains 15% water, almost all plants cannot survive. On the contrary, if water potential is used as the unit of measurement, the measurement results are independent of the nature of the soil. Regardless of the nature of the soil, regardless of geographical location, the soil at -10 bar is very dry, and the soil at -0.5 bar is very moist. It can be seen that you cannot judge the degree of drought in the soil by the water content alone. The optimum water content of a plant grown in soil A is 20%. In the case of soil B, this is not the case. Therefore, research on the relationship between plants and the environment using water content is generally not possible. Thousands of people use water content for plant and water research, but their findings cannot be applied to practice. This is not only a waste of human resources, but also a waste of water resources. It can be seen that the measurement of soil water potential and soil water content is of great significance. This paper recommends two instruments for measuring soil moisture and soil water potential. The instrument for measuring soil moisture is TZS-II soil moisture meter. This instrument can quickly determine soil moisture. For water content, please refer to http://; the instrument for measuring soil water potential is TRS-II soil water potential meter, which is easy to carry and simple to operate, in measuring soil water potential. It is widely used, and its detailed introduction can be found at http:// The above is my understanding and insights on soil water potential and water content, I hope to help you.

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