Introduction to Soil Moisture Analyzers and Common Soil Moisture Measurement Methods

Soil moisture measurement is performed to understand the actual water status of field soil so that irrigation, moisture conservation, or drainage can be carried out in time to ensure normal crop growth, and to relate crop performance and cultivation practices to the water and fertilizer conditions for high yields. Common methods include loss-on-drying, electrical resistance, and neutron scattering; in addition, a soil moisture analyzer can be used for direct moisture testing.

Overview of soil moisture measurement methods:

1. Loss-on-drying: the most common and the standard method for soil moisture. A soil sample of a given mass is collected in the field and dried in an oven at 105 °C. Drying is complete when two consecutive weighings are constant. The moisture lost on drying is the soil moisture content. The formula is: soil moisture = W/M × 100%, where M is the soil weight before drying and W is the weight of soil water, i.e., the difference between M and the dried soil weight M1.For example, the VicoMeterVM-E50With a halogen moisture analyzer, soil moisture content can be determined within minutes at the press of a single key.

2. Electrical resistance method: this method exploits the relationship between the electrical resistance of gypsum, nylon, or fiberglass units and their water content. These intermediates, fitted with electrodes, are placed in moist soil until their water content reaches equilibrium. Because of the resistance–moisture relationship, once the correspondence between resistance and percentage has been calibrated, moisture readings can be obtained over the 1–15 atmosphere suction range through these components.

3. Neutron method: suitable for field soil moisture measurement. It is based on hydrogen atoms, which sharply slow down and scatter fast neutrons. Neutron moisture meters are now commercially available. They offer many advantages, but are considerably limited for organic soils and are unsuitable for measuring moisture in the top 0–15 cm of soil.

4. Soil moisture analyzer: the WKT-M1 rapid soil moisture tester consists of a handheld recorder, soil sensors, a USB data cable, a power adapter, and a portable carrying case. It measures moisture, water potential, temperature and humidity, available nitrogen, available phosphorus, available potassium, and organic matter in soil, plant, chemical fertilizer, and bio-fertilizer samples, as well as soil pH and salinity, and total nitrogen, phosphorus, and potassium in plants. It provides a reliable basis for specialized, systematic, information-based, and data-driven agriculture and is an essential instrument for soil testing and formulated fertilization in agricultural departments.

There are many ways to measure soil moisture. Beyond the traditional methods, modern soil instruments can be used to monitor soil moisture precisely, enabling more scientific irrigation and drainage—safeguarding suitable crop growth conditions while reducing unnecessary water waste, building water-saving agriculture, and promoting sustainable agricultural development.