DJI Agras T16 sprayed apple in Serbia

October 11, 2020 by No Comments

Apple production in Serbia has been traditionally successful, while in the last decade it is the fastest growing agribusiness in all agriculture. Most of production is exported to Russia and the EU. Yield per hectare is from 50 to 70 tons. All varieties of apple are produced and in order to achieve the best yields and fruit quality, all agro technical measures are applied. One of those measures is fruit thinning, which we carried out by drones DJI agricultural drone


*1. Purpose of the Spray

Treatment was a part of recommended technology in apple production. Main goal was to achieve fruit number reduction on fruit branches, fruit size incensement and better coloring and quality of fruit


*2. Info of the Environment

Date of Spray May 5th 2020,

May 8th 2020

Location Ogar, Srem region, Serbia
Type of Terrain Flat land w. gentle slope changes (+/- 5m on 200m section) Temperature(℃) 13-25
Total sprayed Area(ha.) 10 ha Humidity 45-60%
Wind speed(m/s) 2-4 m/s Wind direction SE

The effect of the chemical we used changes with the temperatures, as well as spraying efficiency which drops in higher temperature due to mid-air evaporation, so we chose to work in the morning while below 30C. Attention to the wind intensity was necessary, as spraying above Beaufort level 2 can lead to uneven spraying deposit and contamination of neighboring plots.


*3. Operation Parameters

Type of Drone DJI Agras T16 Firmware Version v02.01.0312
Operation mode Intelligent route planning w. manual override Operation Speed 2.5 m/s
Operation height(from the top of the crop) 2.5 m Line spacing/width 3.2 m
Liquid amount sprayed per hectare 60 lit/ha Nozzle type XR11001VS

The spacing coincides with the spacing in the rows of plantations, as it was important for the chemical to reach each fruit branch. Therefore,flight was performed over each row and used a slightly larger amount of liquid for this mode of operation.

*4. Info of Chemicals

Chemical commercial name Formulation Active ingredient and the percentage Chemical amount used per hectare
Brevis SG Metamitron (15%) 1.10 kg/ha
Exilis SL 6-Benzyladenine 0.75-1.00 lit/ha

Selection of chemicals as well as dosages and the moment of the treatment is based on huge experience and large number of trials that were done during last decades. There are lot of critical parameters in this treatment and interaction between all of them is crucial to success. Fruit clone sensitivity and relation between chemical dosage and climate parameters have to be monitored all the time and the team have to be ready to react in the moment when even one of parameters go out of the order.














  1. Briefly compare the difference between drone, manual, and other traditional equipment in this case.

Main advantage of drone application is precise deposition on top and middle sections of the fruit tree with targeting areas of fruit branches, next to avoidance of spraying punching trough rows. That was important because different clones with different demand for chemical treatment are planted every four rows.Mode of action of hormonal chemicals used for fruit drop is based on chemically induced decrease of plant physiological activity. That is the reason why this operation is critical and has to be maintained by care. If the dosage is over the limit all the fruits will drop, if it is under-dosed fruits will not drop but pygmy fruits with poor calibration and quality will occur. Consequence of temporary physiological decrease is that fruit branches that have 5 fruits differently sized will drop smallest fruits. King fruit as well as, usually, by size, two following King fruit, persist on the branch. Result is that all the fruits on the branch are very similar in size/calibration, color and quality.

At preparation stage, we performed geodetic and multispectral scanning of the orchard, using DJI Matrice M210 RTK V2 w. D-RTK2, X4S and third party six channel camera. Produced orthomosaicmultispectral maps were valuable for fruit tree classification. DJI Terra v.2.1 successfully produced RGB geodetic products from X4S images, while “Fruit tree” automatic missions generationresulted in flight lines of changing altitude, based on terrain and orchard lines. As there were no waypoint and flight path inspection tools in DJI Terra v.2.1, we couldn’t assure that calculated flight path considered thin obstacles (wires, poles, and branches) and varying density of the canopies. Therefore, we decided to perform radar-based altitude guidance and calibration point orientation for each spraying section w. operator supervision and manual override where necessary. Sections and calibration points were defined in DJI Terra “Field” mode, flight lines direction and spraying width were set manually per section tocorrespond to calibration point and orchard lines, as line by line had to be treated with specific treatment(each 4 lines of orchard, approx. 1ha per section). Altitude guidance based on radar was tricky to perform, as objects underneath the aircraft had very variable height (ground, trees, poles and cables), while canopies were of variable density (so radar picked up very varying reference and obstacles) – therefore constant observance and manual correction of flight altitude by the operator were necessary.

Regardless of the beforementioned challenges, spraying operation was performed much more precisely and much faster than it could be done with alternative classic machinery. Potential of drone-based spraying to quickly stop and precisely continue its operation, to swiftly vary spraying path, altitude and spraying rate based on environmental/canopy changes, provided drone spraying with much more precision that it is available with classic machinery. DJI Agras T16 homogenous spraying density was of great benefit in this application, so we find that this task could hardly be accomplished with drones of previous generations (without airflow consistency). Therefore, this challenging spraying mission was performed with top quality and precision, what was unachievable until advent of T generation of spraying drones.

*6. Conclusion

Fruit number reduction is very delicate operation. Large number of variables can influence treatment performance. Temperature, insolation, humidity, cloudiness, biological stage of fruit trees, susceptibility of clones to chemical treatment are some of them. Main benefit of drone treatment was precise application, avoiding contact of non-tolerant apple clones with non-adequate active ingredients, as well as large benefit in logistics and efficiency. Fruit number reduction was successful.


*7. Service team info

The AGRODRON team is the first company in Serbia and the region to deliverprofessionalUAS spraying technology and its regular application in the protection of agricultural crops using own fleet of DJI Agras T16 aircraft. Team gathers experienced drone operators, agronomist, mechatronics, sensing and data specialistand trainers. In our work so far, we have been very successful in treating all types of orchards that are represented in region, all with the aim of promoting new technology and the benefits it brings.

Contact persons: MomirAlvirović, Goran Iskić, Zoran Stojanović.

Contact info: [email protected]

*8. Link of pics or videos:











Warm prompt: the content and parameters provided here are just for reference. You should adjust the operation mode and the parameters and use a correct way to spray your field according to the different weather, the crop characters, the habit or history of using chemicals(you could change other chemicals in case that the resistance occurs), etc. If you are not sure what operation parameters you will choose or not sure about the spraying efficacy, then you should firstly do a small plot test in this field before a big area spray.

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