Soil moisture, as defined in agriculture and forestry, is the amount of moisture present in the soil. Gardeners, farmers, foresters, and even engineers measure soil moisture to identify whether or not the land is suitable for their work. If you’re interested in gardening or landscaping, measuring the soil’s moisture content should be important to you.

How to Measure Soil Moisture

Before we even discuss how to measure soil moisture, we should first discuss the various factors that contribute to it.

Factors Affecting Soil Moisture Measurement

Soil Texture

Soil texture is the ratio of sand, silt, and clay-sized particles that make up the minerals in the soil. The mixture of these various particles creates various textures such as sandy, loam, clay loam, silty clay loam, and many others. These textures are classified into several texture groups based on what they feel like when held. These groups can range from very coarse, moderately coarse, moderately fine, to fine.

Coarse soil allows more water to penetrate it, while fine soil allows fewer amounts of water to pass through. Loamy soil is the best to use when planting trees, shrubs, or herbs. This is because loamy soil belongs to the moderately fine group and has a good proportion of sand, silt, and clay. This means that the right amount of water and air can pass through, making it capable of holding a good amount of organic matter.

Soil Porosity

Soil porosity is the amount of space available within soil particles. This property describes the soil’s ability to facilitate the presence and movement of air and water within itself. As mentioned earlier, loamy soil is the best type of soil to use when planting flora in your area. This is because its porosity is wide enough to facilitate air and water to the plants while still being tight enough to prevent erosion.

Soil Aggregate

When talking about soil aggregate, the best way to put it is to think of clumping various pieces of clay together. The same happens to the particles of the soil. A soil with a good amount of aggregation protects the soil from being eroded by air and water while also preventing them from escaping the soil. A type of soil that has good aggregation is loam. Its particles are aggregated enough to prevent air and water from eroding it while still having enough space to allow these elements to flow.


The climate of the environment has a direct influence on the amount of moisture present in the soil. It can affect this through precipitation and temperature. It can also indirectly influence soil moisture through vegetation. A climate that is suitable for most plants to grow has higher rates of soil water extraction. For example, rainforests with humid and rainy climates have soils that possess a high moisture content.

Additional Reading: Current Soil Moisture Conditions

Measuring the Soil’s Moisture Content

To measure the soil’s moisture content, we will have to do some science and math.

  • Get a considerable amount of soil which you want to test.
  • Get 2 aluminum dishes and measure their weight.
  • Allocate 50g of soil to each dish. To get 50g, weigh the dish with soil and subtract the initial weight of the dish.
  • Dry the soil overnight at 105 °C in the oven.
  • Once done, measure the weight of both dishes again.

The first weight of the dish that you put soil into is called moist soil (M) and the weight of the dish that you dried overnight is called dry soil (D). To get the soil’s moisture content, subtract the weight of the dry soil (D) from the weight of the moist soil (M) (M – D). Then, divide the difference by the weight of the dry soil. After that, multiply it by 100 to get its percentage.

To get an idea about what your percentage indicates, the ideal amount of soil moisture in the soil is around 10% to 18%. Having too high or too low of a percentage can indicate that it is too dry or too wet, so take note of this if you’re planning to plant trees, shrubs, or herbs in your garden.

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