Comprehensive water management capability, including soil moisture sensing, intelligent irrigation, and water supply monitoring, are important Internet of Things use cases for crop production. Additional IoT capabilities focused on assessing soil composition potentially provide even more essential information to help farmers save money, increase yields, and improve quality.
Sampling by extracting “cores” from areas of interest has been the standard for assessing soil composition for many years. Using a device inserted into the ground to extract a cylinder of earth, cores are obtained in multiple spots, typically in a grid-like pattern, to develop a profile for a large area. The samples are then assessed in a lab environment to measure important parameters like salinity and pH, and to determine nutrient levels.
IoT sensing is a potential alternative to the soil core method, automatically capturing data for soil attributes, including:
- pH
- Salinity
- Phosphorus
- Potassium
- Nitrate
- Oxygen
- Organic Carbon
The typical device configuration uses sensors attached to a probe, positioned so that they contact the soil when the probe is inserted into the ground. Multiple sensor types (pH, Nitrate, Potassium, etc.) are often installed on a single device. Depending on the required depth, different-length probes can be used. Configurations for sensing at multiple depths with a single probe are also available.
Most probe designs include a portion of the device that remains above the ground to house the network communications components, the battery, the antenna, and sometimes solar panels. The wireless network connectivity transmits the data to an application (typically in the cloud) for analysis and visualization, eliminating the need to physically access the site to obtain readings. LoRaWAN and Cellular NB-IoT are popular options due to the need to transmit data over distances and effectively manage battery life, not to mention the remote aspect of many agricultural settings. And, very recently, even satellite communication has become an economical option for sensors deployed in even more remote locations.
The most efficient method of installing probes in the ground, where a hole is drilled with an augur for the probe to be inserted (often known as “Drill and Drop”), is ideal. However, this may not be practical due to the need for firm sensor contact with the soil and the care required to avoid damaging sensor surfaces. Adding water, packing soil around the probe before it is inserted, and putting additional soil in the hole are potential requirements. Like the soil core assessment, creating a profile for an entire field requires a determination of how to distribute probes to provide sufficient samples.
The goal is to eliminate or reduce the frequency of manually extracting soil cores and conducting lab tests. Once implanted, the devices can take readings periodically for an extended period—at least a year and often as long as a few years.
Continuous measurement is a potential game-changer, creating a monitoring capability for making decisions using up-to-date information. For example, nutrient levels can help determine the choice of fertilizer and increase or decrease the amount used in future applications. While the IoT sensors provide a wealth of data, it takes someone with the appropriate expertise, typically an agronomist, to analyze the data and turn it into actionable information.
Putting all the information together into an application requires a thorough understanding of IoT technologies, including sensor interfaces, connectivity, and data management. In addition, a robust IoT platform is essential to making the potentially huge amount of sensor data useful and actionable.