As populations have grown, as food production has increased, as economic activity has developed and as societies have become more affluent, so demand for water has burgeoned. Climate change adds yet more pressure on our limited water resources. In very many places demand has far outstripped supply – this may be particularly so in seasons when supply may be severely limited or in years of drought, or at times when demand is particularly high, for example when there is great demand for water for irrigation.

Soil moisture sensor can help automate irrigation

Automated irrigation equipment

Not a new challenge

There have already been multiple approaches to optimizing processes in farming related activities. Some of the latest solutions include: monitoring local variations in soil, drainage and evaporation, in order to ensure uniform irrigation, accurate dendrometers, capable of measuring changes in a plant’s diameter of only a few micrometers to measure water intake or sensors that measure the conditions for photosynthesis.

These solutions are applicable both to open field and greenhouses, where it monitoring and controlling micro-climates is important. Gas sensors can also be of interest in certain environments.

Prone to human errors

Efficient irrigation practices provide a consistent moisture supply to crops, water deficiencies can be overcome during periods of drought, more than one crop cycle per year can be achieved and the effective use of all production resources can be improved dramatically. The pressure on the diminishing water resources can also be alleviated and, as a result, more land can be put under irrigation.

As an example of a specific case, here is an overview of the process on cultivating in greenhouses. The agronomists, during their usual check visit, manually perform the activities of ground sensing and vegetables evaluation. In this step, they store on paper notes all qualitative information detected.

Captured parameters are then processed. Based on this information the agronomist takes decisions and applies actions on plants and grounds. They need to annotate all performed operations (i.e., irrigation, sowing and treatments with plant protection products) on paper that is later saved into a digital system. It is a management software tool that allows the farm to carefully store very important information about the operations carried out on plants, the adopted cultivation methods, and the use of approved cleaning products. Some activities, such as irrigation and temperature control, are executed in automated manner through remote terminal units and an advanced computerized control system.

Introducing wireless sensors in farming

The concept of using a soil moisture sensor to activate irrigation scheduling is well-known and has become a common practice. A large number of soil moisture sensors have become available after the introduction of dielectric soil water. The main parameters to monitor are soil volumetric water content (VWC) and the soil electrical conductivity (EC).  For precision real-time irrigation control, controllers and sensors are installed at each plot or at least at every group of sprinklers or drippers in the field. Each controller performs an individual irrigation schedule which is set and reprogrammed on a regular basis.

In general, field require a large number of sensors in each irrigation zone to obtain a reliable soil moisture reading. Many controllers and sensors are involved and so far the cost for investment, installing wiring, maintenance and data-handling have been a bottleneck. This has forced growers to look for new improved and cost-effective monitoring and control systems.

This is the reason why Wireless Sensor Networks have been introduced in this industry. Installation and management cost is dramatically reduced while providing very similar results to users.

Passive RFID sensor opportunities

Passive RFID tags have always been a nice solution to track and monitor different items. The fact that we can now use sensors within battery-free tags opens a new field of opportunities in smart solutions for farming.

In particular, soil moisture, temperature and EC would be of great interest for the agriculture industry. A wireless battery-free RFID sensor tag providing information about soil moisture, soil temperature and soil EC would greatly help automate monitoring of soil conditions and data processing.

  • Soil moisture sensor. Knowing the moisture level of the soil before actually irrigating the specific area will lead to increased efficiency by saving up to 40% of water.
  • Soil temperature and ambient temperature sensors. These sensors are used for both humidity sensor compensation and to prevent the irrigation system from acting when the temperature would cause the water to freeze, which is not recommended in many situations.
  • Soil Electrical Conductivity. Knowing the nutrient composition of the soil water in advance allows the user to prepare the water nutrient concentration that will best serve the crops or plants each time the irrigation occurs.

This is how an RFID sensor system would work:

  1. Battery-free RFID sensor tags are correctly located in the field. Specific location will depend on the field, crops and finite areas the farmer wants to monitor. Note that battery-free sensor tags are easy to move from one location to another.
  2. RFID readers are used to gather ID and sensor data from the field. Sensor data is uniquely associated to the ID of the tag. This helps automating data collection and processing without introducing error prone activities such as documenting data by hand. When implemented in a more automated farm, RFID readers can be mounted on center pivot irrigation or similar systems to directly receive data from sensors while the machinery moves above the crops/plants.
  3. A robust data processing software will divide water and nutrient requirements by field areas and decide the quantities of water and nutrients the system needs to deliver in each area for optimized growth.
  4. The irrigation machinery will deliver the proper amount of supplies to the crops/plants according to the areas defined by the processing system.

By introducing wireless sensors in the farming industry, growing crops and plants can be greatly optimized. The main advantages of using an RFID sensor system are:

  • Water consumption is reduced.
  • Crops productivity is increased.
  • Water consumption is tracked and water tariffing is enabled.
  • Unauthorized water consumption is detected.

Battery-free RFID sensor systems reduce the investment in sensor devices and maintenance costs are decreased because these do not require battery changes. Thus, these systems can be a very good fit for irrigation systems in the farming industry.