Sensors are useful in various research areas. For instance, a PT 100 sensor is used to measure temperature. Similarly, there are other sensors which are used for monitoring macro-climate. In addition, wireless sensors (which are generally known as nodes) could be used to record microclimatic parameters within the crop canopy. Normally they are set up at certain distance depending on their precision and all of them communicate to a remote data logger or server where this information is collated and used for further analysis. This data is useful for modeling purposes either for predicting the yield or for forewarning pests. In this article, we will explore how these sensing technologies have been woven into modern large agribusiness and discuss how progression of the technology both to small
farms at home as well as globally can increase our capacity to feed the world.
Agricultural Sensors:
A number of sensing technologies are used in precision agriculture, providing data that helps farmers monitor and optimize crops, as well as adapt to changing environmental factors including:
1. Location Sensors use signals from GPS satellites to determine latitude, longitude, and altitude to within feet. Three satellites minimum are required to triangulate a position. Precise positioning is the cornerstone of precision agriculture. GPS integrated circuits like the NJRNJG1157PCD-TE1 are a good example of location sensors.
2. Optical Sensors use light to measure soil properties. The sensors measure different frequencies of light reflectance in near-infrared, mid-infrared, and polarized light spectrums. Sensors can be placed on vehicles or aerial platforms such as drones or even satellites. Soil reflectance and plant color data are just two variables from optical sensors that can be aggregated and processed. Optical sensors have been developed to determine clay, organic matter, and
moisture content of the soil.
3. Electrochemical Sensors provide key information required in precision agriculture: pH and soil nutrient levels. Sensor electrodes work by detecting specific ions in the soil. Currently, sensors mounted to specially designed “sleds” help gather, process, and map soil chemical data.
4. Mechanical Sensors measure soil compaction or “mechanical resistance.” The sensors use a probe that penetrates the soil and records resistive forces through use of load cells or strain gauges. A similar form of this technology is used on large tractors to predict pulling requirements for ground engaging equipment.
5. Dielectric Soil Moisture Sensors assess moisture levels by measuring the dielectric constant (an electrical property that changes depending on the amount of moisture present) in the soil.
6. Airflow Sensors measure soil air permeability. Measurements can be made at singular locations or dynamically while in motion. The desired output is the pressure required to push a predetermined amount of air into the ground at a prescribed depth. Various types of soil properties, including compaction, structure, soil type, and moisture level, produce unique identifying signatures.
7. Agricultural Weather Stations are self-contained units that are placed at various locations throughout growing fields. These stations have a combination of sensors appropriate for the local crops and climate. Information such as air temperature, soil temperature at a various depths, rainfall, leaf wetness, chlorophyll, wind speed, dew point temperature, wind direction, relative humidity, solar radiation, and atmospheric pressure are measured and recorded at predetermined intervals. This data is compiled and sent wirelessly to a central data logger at
programmed intervals. Their portability and decreasing prices make weather stations attractive for farms of all sizes.
