A few years ago, drone technology seemed to be an unreachable facility for poor farming communities, but gradually, things have changed a lot.
At present, drones are used in the agriculture field for various essential farming operations such as crop management and monitoring, weed detection, irrigation scheduling, disease detection, pesticide spraying, and gathering data from ground sensors.
The deployment of drones in precision agriculture is a cost-effective and time-saving technology that can help for improving farm productivity, crop yields, and profitability in farming systems. Drones facilitate agricultural management, weed monitoring, and pest damage; thereby, they help meet these challenges quickly.
Drones can be efficiently used for small crop fields at low altitudes with higher precision and low cost than traditional manned aircraft. Using drones for crop management can provide precise and real-time data about a specific location.
Moreover, drones can offer high-resolution images for the crop to help in crop management, such as disease detection, monitoring agriculture, detecting the variability in crop response to irrigation, weed management, and reduce the number of herbicides.
Irrigation scheduling
Four factors need to be monitored to determine a need for irrigation: 1) Availability of soil water; 2) Crop water need, which represents the amount of water needed by the various crops to grow optimally; 3) Rainfall amount; 4) Efficiency of the irrigation system. These factors can be quantified by utilizing drones to measure soil moisture, plant-based temperature, and evapotranspiration. For instance, the spatial distribution of surface soil moisture can be estimated using high-resolution multispectral imagery captured by a drone combined with ground sampling. The crop water stress index can also be calculated to determine water-stressed areas by utilizing thermal drone images.
Plant disease detection
According to estimates, in the U.S., the crop losses caused by plant diseases result in about $33 billion in yearly lost revenue. Drones can be used for thermal remote sensing to monitor crop diseases’ spatial and temporal patterns pre-symptomatically during various disease development phases. Hence, farmers may reduce crop losses. For instance, aerial thermal images can be used to detect early-stage development of soil-borne fungus.
Soil texture mapping
Soil properties, such as soil texture, can indicate soil quality which in turn influences crop productivity. Drone thermal images can quantify soil texture by measuring the differences in land surface temperature under a relatively homogeneous climatic condition.
Residue cover and tillage mapping
Crop residues are essential in soil conservation by providing a protective layer on agricultural fields that shields soil from wind and water. An accurate assessment of crop residue is necessary for the proper implementation of conservation tillage practices. Aerial thermal images can clearly explain more than 95% of the crop residue cover amount variability compared to 77% using visible and near IR images.
Field tile mapping
Tile drainage systems remove excess water from the fields, and hence it provides ecological and economic benefits. Efficient monitoring of tile drains can help farmers and natural resource managers better mitigate any adverse environmental and economic impacts. By measuring temperature differences within a field, thermal drone images can provide additional opportunities in field tile mapping.
Crop maturity mapping
Drones can be a practical technology to monitor crop maturity for determining the harvesting time, particularly when the entire area cannot be harvested in the time available. For instance, drone visual and infrared images from barley trial areas at Lundavra, Australia, were used to map two primary growth stages of barley and demonstrated classification accuracy of 83.5%.
Crop yield mapping
Farmers require accurate, early estimation of crop yield for several reasons, including crop insurance, planning of harvest and storage requirements, and cash flow budgeting. Drone images are utilized to estimate the yield and total biomass of rice crops in Thailand. Drone images also predict corn grain yields in Germany’s early to midseason crop growth stages.
Challenges
There are several challenges in the deployment of drones in PA:
- Thermal cameras have poor resolution, and they are expensive. The price ranges from $2000-$50,000 depending on the quality and functionality, and the majority of thermal cameras have a resolution of 640 pixels by 480 pixels.
- Thermal aerial images can be affected by many factors, such as moisture in the atmosphere, shooting distance, and other emitted and reflected thermal radiation sources. Therefore, calibration of aerial sensors is critical to extract scientifically reliable surface temperatures of objects.
- Temperature readings through aerial sensors can be affected by crop growth stages. When plants are small and sparse at the beginning of the growing season, temperature measurements can be influenced by reflectance from the soil surface.
- In adverse weather, such as extreme wind, rain, and storms, drones’ deployment in PA applications is a big challenge. In these conditions, drones may fail in their missions. Therefore, small drones cannot operate in extreme weather conditions and cannot even take readings during these conditions.
- One of the critical challenges is the ability of lightweight drones to carry a high-weight payload, limiting the ability of drones to carry an integrated system that includes multiple sensors, high-resolution and thermal cameras.
- Drones have a short battery lifetime, usually less than 1 hour. Therefore, the power limitations of drones are one of the challenges of using drones in PA. Another challenge, when drones are used to cover large areas, is that it needs to return many times to the charging station for recharging.
