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Technology plays an important role in the sustainable intensification of the agricultural system. Scientists have revealed that the use of sensors in agricultural farming has increased the growth and yield manifold, and has also significantly reduced the costs of production. A sensor is a device that can accumulate information and convert it to electrical signals or other forms of output as required. Owing to the advancement of Internet of Things (IoT) technology, sensor applications in agriculture and other industries have increased rapidly.
There are different kinds of sensors, such as temperature, humidity, soil content, soil moisture, soil pH, light intensity, and pathogenic infestation that are used in the agricultural system. These sensors can monitor different stages of plant growth and the conditions under which they are grown.
Technologies Used to Develop Sensors
Location sensors use GPS satellites to determine the longitude, latitude and altitude, i.e., the topographic attributes, which are useful in the precise positioning of precision agriculture.
Typically, at least three satellites are required to triangulate a position. This sensor is used in vineyards to optimize the patterns of crop growth and yield. They are also useful when interpreting yield maps and weed maps. Furthermore, these assist in farm planning by analyzing field boundaries, existing roads and wetlands.
This sensor uses light to measure various properties of soil. The basic working principle of optical sensors is that they measure the different frequencies of light reflectance in mid-infrared, polarized and near-infrared light spectrums.
Optical sensors can be installed on vehicles, drones and satellites. They record plant color and soil reflectance, which can be processed and analyzed for scientific conclusions.
Optical sensors also help in determining the organic matter and moisture content of the soil. Several optical sensors such as light curtain imaging, laser distance sensors, 3D Time-of-Flight cameras, hyperspectral imaging, and color imaging are integrated and used.
The amount of nitrogen uptake by a plant is monitored by a three-sensor system based on the canopy spectral reflectance. In photosynthesis, chlorophyll plays a vital role. When the plant tissues containing chlorophyll are excited by a light source, it fluoresces, and the chlorophyll fluorescence is monitored by the red and far-red light emitted by the photosynthetic tissues. A chlorophyll fluorescence sensor helps determine the health of a photosynthetic sample.
This sensor helps to monitor the pH and nutrient content of the soil. The sensor electrodes help detect specific ions present in the soil, which assesses the ionic profile of the soil.
This sensor helps to measure soil compactness. The probe is inserted in the soil to measure the resistive forces via load cells and strain gauges.
This type of sensor is used to evaluate the moisture levels in the soil. It measures the dielectric constant which is the change in the electrical property owing to the moisture content of the soil.
What is IoT and what does it mean for farmers?
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Sensors Used in Agriculture
Farmers use several sensors to understand the environmental conditions and plants’ requirements to optimize the yield. Some of the widely used sensors are as follows:
Microorganisms and pest sensors
Many fungal infections can be associated with temperature and humidity conditions. Early detection allows the farmer to protect the crop from widespread infections.
Microbial, viral, or pest infection causes a huge loss in agricultural production. For remote automatic pest monitorization, a pest insect trap is attached with low-power image sensor technology. These traps form a Wireless Sensor Network (WSN) and the images are sent through wireless one-hop broadcast communication to a host control station.
Microbial root colonization in potatoes can be detected by a confocal laser scanning microscope by analyzing the metabolites produced by the microbes, which fluoresces. Zymoseptoria tritici in wheat can be detected by Infrared Thermography technology.
In crop development, analysis of soil is an essential factor as it directly influences the growth and yield of the plant.
Spectroradiometer is the sensor associated with the hyperspectral analysis of soil contents, i.e., nitrogen, carbon, and organic matter, based on regression trees.
Frequency-domain reflectometry is used to determine the soil salinity by assessing its electrical conductivity. Time-domain reflectometry (TDR) can analyze moisture, temperature and electrical conductivity of the soil.
Soil moisture determines the water supply status of the crops. When the soil contains a balanced amount of water, the leaf transpiration and water absorption in roots are in equilibrium, which is the most suitable condition for plant growth. Thereby, the soil moisture sensor measures the dielectric constant of the soil and determines its moisture content. Similarly, the pH of the soil is determined using the electrode sensors.
This sensor is mostly used in greenhouse agricultural planting. It can help growers to accurately understand the sunshine time law, light saturation point, and light compensation point of plant growth. This sensor can monitor the light intensity of 0 to 200,000 Lux with a very short response time.
Air temperature and humidity Sensor
This sensor can monitor the changes in temperature and humidity around agriculture fields.
Smartphones in Agriculture
Smartphones with several applications are used in farming. These applications collect data from handheld sensors, remote sensors and weather stations.
They process the data and provide valuable recommendations. They also have a wide range of functions, including fertilizer calculation, soil study and leaf color analysis.
A water study can also be carried out by determining the leaf area, helping farmers to determine the plant’s water requirement. The applications can also detect phytopathogens and accurately predict harvest time.
Some of the companies which manufacture several types of agricultural sensors are Renke Control Technology Co., Ltd. (China), Tule Technologies (California), Motorleaf (Canada), Pycno (London), Amber Agriculture (Minnesota), and Acuity Agriculture (California).
References and Future Reading
Schriber, S. (2021) Smart Agriculture Sensors: Helping Small Farmers and Positively Impacting Global Issues, Too. Mouser Electronics. [Online] Available at: https://www.mouser.co.uk/applications/smart-agriculture-sensors [Accessed 1 April 2021]
Renke.com (2021) Renke’s Official Website. [Online] Available at: https://www.renkeer.com/index.php/index/lists/catid/14.html [Accessed 1 April. 2021]
Amber.ag. (2021) Amber’s Official Website. [Online] Available at: https://www.amber.ag/ [Accessed 1 April 2021]
Acuity Agriculture (2021) Acuity Agriculture’s Official Website. [Online] Available at: https://www.learn.acuityagriculture.com/products-services [Accessed 1 April 2021]
Pycno.co. (2021) Pycno’s Official Website. [Online] Available at: https://pycno.co/ [Accessed 1 April 2021]
Pajares, G. et al. (2013) Sensors in Agriculture and Forestry. Sensors, 13(9), pp. 12132-9. DOI: 10.3390/s130912132