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Agricultural drones: One should be able to fly

By Anne Ehnts-Gerdes, DLG Press Releases

Drones can be used in a variety of ways in agriculture: these remote-controlled flying objects can not only provide aerial and thermal images for damage detection, surveying, inspecting photovoltaic systems or searching for fawns and wild boar. Thanks to state-of-the-art sensor technology, they also provide valuable information for field scoring or partial area management. In addition, carrier-only drones can be used with the appropriate spreading and spraying technology to apply resources. This is where the drone really comes into its own when the field is not passable due to the stage of development of the crop, its topography or weather conditions.

Two different types of drone

Fixed-wing drone: The fixed-wing drone is similar to a model airplane and achieves the majority of its lift via fixed wings. This type of drone achieves high area performance, but requires a runway, which is unlikely to be available on every field and at all times of vegetation.

Multicopter: Not so the multicopter drone. It can take off and land vertically quickly and safely, as it works in a similar way to a helicopter and actively generates all of its lift via vertically arranged motors with propellers. Although this means it requires comparatively more energy, it is less susceptible to wind. Only gusts of wind from around 40 km/h force the multicopter drone back to the ground. With tare weights of up to 150 kg and payloads of up to 50 kg, this type of drone is the choice when it comes to deploying resources. However, depending on the additional weight, a comparatively large amount of battery power is required. The flight time is correspondingly short (12 to 45 minutes) and the working speed is low (5 to 10 m/s). With an appropriate number of batteries and charging technology on site, the multicopter can still be used efficiently as a spraying and spreading drone. It flies the field regardless of the direction of cultivation so that turning maneuvers are reduced to a minimum. 

Weight: the limiting factor

The cost-effectiveness of using drones is primarily influenced by their own weight or the required application rate of the fertilizer. This is why traditional fertilization with both granulated and liquid products is still not an aerial job. The agricultural drone is always a serious alternative to the field sprayer and fertilizer spreader when light operating materials are to be applied at low application rates.

Possible applications for agricultural drones

Biological plant protection: 
Drones have already proven themselves in biological plant protection compared to conventional methods. In maize, for example, for the application of Trichogramma capsules to control the European corn borer - a measure that is usually carried out twice in the crop in June/July. The beneficial insect capsules are just a few milligrams in weight, meaning that devices with a payload of 7 kg, for example, are sufficient. Other beneficial insects that can be applied by drone include lacewing larvae against aphids, predatory mites, nematodes or Bacillus Thuringiensis. A comparatively new field of application for drones, especially in the area of municipal services, is oak processionary moth control. This involves spraying the treetop with a biological insecticide from May onwards.

Chemical plant protection: The use of drones in chemical plant protection has only been permitted in the EU for two years, but is still legally restricted to viticulture on steep slopes. Although the JKI has only listed two types of drone so far, they are already increasingly replacing helicopters in viticulture. Approval for the aerial application of slug pellets is expected. In the medium or long term, it can be assumed that agricultural drones will also be approved in the EU for conventional plant protection in the field, similar to Switzerland or the USA. However, restrictions are to be expected here due to drift.

Weed mapping and partial area spraying: Another future topic is likely to be weed mapping and sub-area spraying. For example, to specifically spray thistle out of volunteer cereals or for measures against late weeds in beet or maize. So far, the drone only creates the zone map for the field sprayer. In future, it could also be used to treat weed nests and individual plants (spot spraying).

Fertilization and sowing: In practice, drones are already being used to apply micronutrients and microorganisms, urea or biostimulants. In addition, the first drone sowing trials on field emergence and seed distribution with catch crops have been carried out at the South Westphalia University of Applied Sciences. The results so far are very promising. Intercrops can be established before the main crop is harvested to save water. 

Studies on practical utilization

In sowing trials at the South Westphalia University of Applied Sciences a DJI Agras T16 drone was used (dimensions: 2.5 m x 1.8 m x 0.8 m, empty weight without battery 18.5 kg, maximum take-off weight 40 kg). It allows a payload of 15 kg seed and seed rates of up to 35 kg/ha. In order to be able to fly continuously, four batteries and two chargers were used, which require a 6 to 7 kW power supply. The spreading disc works up to 10 m wide, depending on the spreading material. The flight speed is a constant 7 m/s. As a rule, the drone flies 3 to 5 m above the ground during application.

One to two container fillings are applied with one battery charge. The area coverage per flight is 1.5 to 2 ha, depending on the spread rate of the catch crop. In this way, outputs of 4 to 6 ha/h are achieved on small structured areas and sometimes double that on large areas with 10 kg/ha.

What do agricultural drones cost?

Agricultural drones from the Chinese manufacturer DJI are the most common. An agricultural drone of the type mentioned above costs €25,000 to €30,000. In addition, the batteries cost around €1,600 each. If you are afraid of this investment, you can also buy the technology as a service from agricultural dealers and contractors. For the pre-harvest sowing of catch crops with the aforementioned drone, it costs around €30/ha for a spread rate of 15 kg/ha. There may be surcharges for higher quantities. However, the economic viability of the process must then also be questioned at some point.


In certain regions and for special applications, the agricultural drone will be the method of choice in the future. It is versatile, works gently on the soil and plants and can also be used in places where tractors cannot reach or are uneconomical. However, the main limitations are the current legal framework and the quantity or weight of the agricultural inputs.