Soil moisture monitoring is critical for managing water resources in an efficient manner. This applies to both irrigated and rainfed cropping systems. Water is increasingly becoming the most limiting resource needed to meet the food and fiber needs of a growing and more affluent population. Soil moisture monitoring can e.g. be used as a tool to assist irrigation scheduling. Irrigation management gives better crops, using fewer inputs, which increases profitability. Soil moisture sensors help with irrigation decisions. They are useful tools to understand what is happening in the root zone of your crop.
Responds to the following needs
- Food security
- Improved irrigation techniques
- Real-time and remote-sensing capabilities to improve water management and efficiency of use
- Small-scale farmers
- Agriculture industry
- Rain-fed and irrigated agriculture
Relevant CTCN Technical Assistance
- Chile Design of biodiversity monitoring Network in the context of Climate Change
- Ghana Improving resiliency of crops to drought through strengthened early warning
Relevant Technology Needs Assessment
The following list is focused on soil moisture measurement technologies that are inexpensive and simple to use:
- Gravimetric method: The gravimetric method is simple and reliable and is the standard against which all other methods are compared. It is somewhat labor intensive and that is the chief drawback to the method. Another disadvantage is that it requires more than 24 hours to get a result. The method involves taking a sample of soil, placing it in a container of known weight, weighing the container with the moist soil, drying the sample in an oven set at 105 °C for 24 hours, and then weighing the container with the sample again. The difference in weights before and after drying equals the weight of the water. The difference in weights of the container containing the dried soil and the container weight equals the weight of the dry soil. The mass wetness content of the soil is then calculated by dividing the weight of the water by the weight of the dry soil and then converted to a percentage by multiplying the result by 100.
- Feel and appearance method: The feel and appearance method is based on the fact that the feel and appearance of soil vary with texture and moisture conditions. Soil moisture conditions can be estimated, with experience, to an accuracy of about 5 percent. Soil moisture is typically sampled in 3-cm increment to the root depth of the crop at three or more sites per field. It is best to vary the number of sample sites and depths according to crop, field size, soil texture, and soil stratification.
- Soil probe method: Soil probes are simple in design, low cost, easy to use, and yields reasonably good estimates of the amount of plant available soil moisture in the root zone. The principle is that a probe can be easily pushed into a moist soil but cannot be pushed into a relatively dry soil. A soil layer containing more water than required to wet the soil to field capacity will drain by gravity to the underlying layer. Thus, water will continue to move deeper into the soil profile until all the layers above the wetting front have reached the field capacity level. Once the water movement by gravitational forces has stopped, there is little or no additional downward movement of water. Therefore, the depth that the probe can be pushed into the soil profile represents the depth that the soil is wetted to the field capacity level.
There are several other methods of measuring soil moisture including Time Domain Reflectometers, Capacitance Probes, Neutron Probes, Gypsum-Porous Blocks/Electrical Resistance, Calcium Carbide Gas Pressure Meter, and Tensiometers. These are not included above as they are not easily and cheaply adapted to field conditions, particularly in developing countries.
[Disclaimer: Products listed here are provided by Climate Technology Network members and represent examples of products available within this technology field. The CTCN does not take responsibility for this product information and cannot guarantee its suitability in specific contexts or regions.]
- Real time wireless soil moisture monitoring system IRISTAR Pro2 Plus [Republic of Moldova]
- Department of Agriculture and Food, Government of Western Australia
- FAO & Dryland Agriculture Institute