Moisture release curves have always had two weak areas: a span of limited data between 0 and -100 kPa and a gap from -100 kPa to -1000 kPa where no instrument could make accurate measurements. What is soil moisture? Field Capacity is the amount of soil moisture or water content held in the soil after excess water has drained away and the rate of downward movement has decreased.

For example, if the matric potential of some soil is -10 kPa (kilopascal), then the moisture tension is 10 kPa. Tensiometric measurement-measuring the physical force actually holding water in the soil, measured in Centibars (or kPa) of soil water tension; IRROMETER soil moisture measurement is based on the tensiometric method, as the amount of water is less important than how difficult it is for the plant to extract it … Our IRROMETER Tensiometers, soil moisture sensor instruments provide a direct measurement of soil water tension, which is the tension all root systems must overcome to extract water from the surrounding soil. Simple, reliable, and accurate, the IRROMETER is …

Most people look at soil moisture only in terms of one variable: soil water content. At a typical bulk density … Thus the matric potential of soils or potting mixes generally will negative. The term moisture tension represents the degree of such suction and will be given as a positive number. If you look at a silt loam soil as a kind of medium texture soil, its -33 kPa water content is 27% and its -1500 kPa water content is 13%. There is some truth here. Soil saturation does indeed occur at 0 kPa, at least in general. This usually takes place 2–3 days after rain or irrigation in pervious soils of uniform structure and texture. Soil water content can be measured on a mass or volume basis. Between 0 and -100 kPa, soil loses half or more of its water content.

When speaking about soil moisture in terms of tension, think about psi in the form of suction. Gravimetric soil water content is the mass of water in the soil, measured as the difference between the moist soil and the soil dried at 105°C, known as the oven-dry weight.

Soil water content affects the moisture and amount of nutrients available to plants and soil aeration status.

Measuring Soil Saturation.

For soil saturation, the assigned pressure is 0 kPa.