How agricultural drone spraying systems work
Learn the key parts of drone spraying systems—atomization, RTK guidance, radar/vision, and controls—so you can plan and operate safely.
What “drone spraying systems” are in practice
A spraying drone is not just an aircraft with a tank. It combines propulsion, liquid storage, spray generation, guidance, sensing and a control link. Ground support for mixing, filling, charging and transport is also part of the working system.
The term “agricultural drone” now covers more than plant protection. Early systems were called plant protection drones and focused on pest and weed control. The wider term reflects their use for spraying, spreading seed, fertiliser and feed, as well as field survey work.
Spraying remains a key task. Agricultural drones can follow planned routes and treat set areas rather than blanket a whole field. They can also work over paddy fields, tall crops and mountain land where people or ground machines may struggle.
That does not mean every spray job suits a drone. The aircraft, spray mix, crop, field and legal rules still need to match. Agricultural drones can fall under farm equipment, environmental and civil aviation rules, with oversight varying by country.
This article uses the DJI Agras T50 as a checked example of how the parts fit together. Its main figures can also be compared with other entries in our drone specifications.
Core components: propulsion, spraying hardware and guidance
A spray platform must lift the aircraft, its liquid load and the systems needed to control the job.
The maker describes a coaxial twin-rotor propulsion system and a split-type, torque-resistant structure. The propulsion system supplies lift and creates downwash over the crop. Research on drone spraying says this downwash pushes droplets towards crop surfaces and can help them reach lower parts of plants.
The structure matters because the aircraft must remain steady while carrying liquid. Its load also changes as spray leaves the tank.
The main parts of the example system are:
- a propulsion system and load-bearing airframe;
- a Dual Atomizing Spraying System;
- Front and Rear Phased Array Radars;
- a Binocular Vision System.
These parts have linked jobs. Propulsion keeps the aircraft airborne, guidance holds it to the route, and the spray system creates droplets. The control link gives the operator a way to manage and watch the run.
How onboard spraying hardware works
From tank to droplets
The spray process starts with mixed liquid in the onboard tank. The liquid then passes through the spraying system and is atomised. Atomisation breaks the liquid stream into droplets for release above the crop.
On the DJI Agras T50, DJI calls this the Dual Atomizing Spraying System. Research on agricultural drone work says operators can adjust droplet size through the remote controller. This lets them set droplet output for the planned treatment and coverage needs.
Droplet production is only one part of deposition. Flight height, speed, route spacing and wind can affect where the spray lands. Propeller downwash also pushes droplets down from the aircraft towards the canopy.
Low flight can shorten the path between the outlet and the crop. In a sugarcane case study, agricultural drones worked at 2.5–4 metres above the crop. Fixed-wing aircraft in that comparison worked at about 15 metres, where high speed and height were linked with drift towards nearby crops.
Those heights describe the cited sugarcane work, not a fixed setting for every field. The crop, product and local rules still govern the planned run.
Flow rate and sprinkler layout
Flow rate states how much liquid the spray system can release in a set time. It is not, by itself, a measure of field coverage. Coverage also depends on the application rate, flight route, speed and time spent refilling.
The DJI Agras T50 reaches 16 L/min with two sprinklers. Its maximum flow rises to 24 L/min with four sprinklers. The higher figure therefore depends on a different sprinkler layout, rather than the standard two-sprinkler figure alone.
Tank size and flow rate describe different limits. The flow setting controls how quickly the system can apply that liquid while flying.
A high available flow can support jobs that call for more liquid, but the rate must suit the treatment plan. It should not be read as a reason to run the system at maximum output on every crop.
How the drone stays on task while spraying
RTK position control
A planned spray pass depends on repeatable aircraft position. RTK improves the position data used by the flight system. For the DJI Agras T50, the stated RTK hovering accuracy is ±10 cm horizontally and ±10 cm vertically.
Hovering accuracy is not the same as complete spray accuracy. The figure describes how closely the aircraft can hold its position under the stated mode. Droplet movement after release still depends on the spray set-up and field conditions.
Research on agricultural spraying links RTK with planned routes and targeted treatment. A drone can follow a pre-programmed flight and apply material only to chosen areas. This approach differs from a broad treatment that covers the full field whether each part needs it or not.
Radar and vision
Position data does not describe everything around the aircraft. The DJI Agras T50 also uses Front and Rear Phased Array Radars and a Binocular Vision System. These systems support its work across survey, spray and spread tasks.
The stated obstacle-sensing range is 1–50 m. The specification also gives a 2.5 m safety limit distance. These figures describe the sensing specification, not permission to fly close to any object.
Radar and vision provide information about the aircraft’s surroundings. The flight system can use that input while the aircraft follows terrain and works near field features. Research on agricultural drones says radar and vision sensors support terrain following by helping the aircraft adjust its height over changing ground.
The operator still has a role. Sensors do not remove the need to inspect the site, identify hazards and keep watch during the flight. They are aids within the control system, not a substitute for safe job planning.
Structure and load stability
A spray aircraft carries a moving liquid load rather than a fixed camera. The DJI Agras T50 uses a split-type, torque-resistant structure alongside its coaxial twin-rotor propulsion system. DJI links this design with stable work while carrying spray or spread loads.
Its spraying and spreading limits are different. For spreading, the maximum take-off weight is 103 kg at sea level, while the spreading tank holds 75 L.
Those spreading figures do not set the spray load. They show why operators must check the specification for the task fitted to the aircraft. A platform used for several farm jobs can have different limits in each configuration.
Control and communications for spray runs
The operator needs a control link for planning, command and oversight. The DJI Agras T50 supports offline operations and uses a 2 km O3 Transmission link. An optional relay is also listed for signal support.
The 2 km figure describes the stated transmission link. It should not be treated as a safe working radius or an automatic legal limit. Terrain, field layout and the duty to maintain visual contact can shape the real operating area.
Offline support is useful where a field lacks network service. It means the core operation does not depend on a live network connection. The aircraft and controller still need a sound control link for the job.
Communications are only one layer of guidance. RTK provides precise position data, while radar and vision sense the area around the aircraft. The remote link connects the operator with those onboard systems and the spray controls.
Operators comparing flight planning, field practice and support equipment can find related material in the guides index.
Putting the system together for a spray job
Plan the treatment and field route
The job begins with the treatment area, crop and planned spray. Research describes agricultural drones following pre-programmed flights for targeted work. The operator must also account for field shape, terrain and obstacles when setting that route.
A field check should identify features that the aircraft may meet during the run. Radar and vision can aid flight, but they do not make site checks needless. The route must also fit the control link and the rules that apply at the site.
The spray plan then ties liquid output to the route. Flow, droplet size, flight height and speed must work as one set-up. Changing one part can alter deposition and coverage.
Prepare the ground system
The onboard aircraft is only the flying part of the job. Ground support must provide transport, mixed liquid, filling and battery charging. A spray-drone trailer can bring these parts together near the take-off and landing area.
Research on trailer layouts stresses short refill and recharge steps. Water and batch tanks hold the liquid needed for the work. Pumps and hoses move the mix to the aircraft, while charging equipment supports repeat flights.
The work area should also keep chemicals, batteries, tools and spare parts in set places. Good layout cuts walking and keeps the landing area clear. It can also reduce handling around the aircraft while it is being turned round.
Fill and check the aircraft
The operator must keep the total aircraft weight within the spraying limit.
Before launch, the check should cover the tank, spray system, propellers, sensors and control link. The selected sprinkler layout also matters because it sets the available maximum flow. Two sprinklers support 16 L/min, while four support 24 L/min.
The intended setting may be below those maximum figures. The correct output comes from the treatment plan, not from the largest flow the system can produce.
Fly, sense and spray
During the run, the propulsion system carries the aircraft and creates downwash. The structure helps keep the loaded aircraft steady.
Propeller downwash drives the spray towards the crop.
The operator watches the run through the control link. Offline operation can keep the job independent of live network service.
Land, refill and repeat
When the tank or flight cycle calls for a stop, the aircraft returns to the ground area. The crew refills the spray tank and deals with charging before the next run. A well-laid-out tender area keeps this turn round direct and controlled.
This cycle explains why tank capacity alone does not define output. The full system includes time in flight, liquid flow, route length, landing, filling and charging. Field size and travel between plots also affect the job.
What the specifications do—and do not—tell you
Checked specifications help an operator compare the physical system. For the DJI Agras T50, they establish sprinkler-dependent flow, RTK hovering accuracy and obstacle-sensing range.
They do not prove that one set-up will suit every treatment. Nor do they state the right droplet size, route spacing or application rate for a given product. Those choices depend on the crop, spray plan, label and local rules.
The central point is simple: drone spraying is a linked process. The aircraft must carry the load, hold its route, sense its surroundings and atomise liquid at the planned rate. The control and ground systems must support that work from filling through to the final landing.