Drone Spraying in Orchards

Vegetables & Fruit · July-Aug 2022

The key global challenge of the moment remains the provision of healthy, balanced and affordable meals to a growing global population. Current levels of rural poverty and concerns about natural resource management and public awareness about sustainable practices in food production are prominent.

The economics of cultivation and irrigated agriculture are important topics in precision agriculture that relate to these challenges. In the case o ffruit orchard management, the challenges also concern processors. Within the context of precision agriculture, site-specific management is crucial to enhancing agricultural economics and in reducing environmental impact.

Site-specific management refers to the general stages of orchard variability mapping, collecting data and making decisions. According to Zhang and Kovacs, 2012, it is making it possible to understand all aspects of crop cultivation, including biological, chemical and physical processes.

Leading technology

As a preferred manufacturer of agri drones, the DJI factory is situated in what is known as China’s Silicon Valley. Here they benefit from direct access to the suppliers and raw materials. Their young, creative talent pool are developing and manufacture precision drones for industrial, agricultural, security, landmapping, construction, landscape, equipment and structure surveillances.

Also aimed at fruit orchards, the next generation DJI Agras 40-litre payload spraying drone will leave the factory in Shenzhen for availability in South Africa before the end of 2022.

In fruit orchards, pruning is often aimed at optimised fruit production and protection. However, orchard canopies are making accurate and timely data collection challenging. These limitations in data collection are increasingly managed by using a suitable Remotely Piloted Aircraft (RPA) / Unmanned Aerial Vehicle (UAV) or a drone to obtain data with the required time frequency and spatial resolution (Campos et al., 2019; Matese et al., 2019).

“Compared with satellite-based remote sensing, using UAVs for monitoring is less dependent on weather conditions. For the monitoring of regions covered by significant cloud, UAV yielded a data-acquisition probability of 45% to 70%, while the probability based on satellite was around 20%,” according to Van der Wal et al., 2013.

Drone observations in orchards have been found to have significant advantages:

  • they can be deployed in high-risk situations,
  • data acquisition is fast, and
  • images are geo-referenced (Handique et al., 2017; Saldana Ochoa & Guo, 2019).

The limitations of drones include operational speed and the battery life. Battery life, however, enables drones to operate in relatively small or medium-sized orchards. Their operational speed is lower than that of manned airborne spraying alternatives, says Garcia-Ruiz et al., 2013. To collect data of high quality, a good balance between flying speed and data quality should be maintained during data collection.

Drone advantages and disadvantages

Spraying pests and weeds in orchards can be easier and with an improved product efficacy. Seeing is believing. Fruit and Vegetables joined a recent introduction of the latest UAV technology and benefits at different conditions in South Africa.

Tim Wise, a part-time farmer in KwaZulu-Natal and CEO of PACSys Precision Agriculture Systems, says the impact of precise applications with precise spraying drones means improved cost efficiency and environment conservation through:

  • precision
  • accuracy
  • reliability
  • stability
  • drift reduction and
  • convenience.

Agri drones give farmers more control over their fields, crops, time, finances and success through better crop management, says Wise.

Selecting the most efficient way of herbicide and pesticide application or liquid and granule fertilisers in fruit orchards is key to sustainability through long term savings and profitability. Agri drones seem to be part of the solution, but there are strict requirements applying to owners and operators.

Legal requirements

Any drone spray contractor must have a company level licence (12-18 months). A drone level license (a serial number from Civil Aviation) and pilot level license are also essential, says Wise. It is legally required to show prove of possession of an official, updated Remotely Piloted Aircraft (RPA) if you are a drone owner or a contractor.

The South African Civil Aviation Authority (SACAA) is regulating all drone operations within the borders of the country.

As is the case with all agricultural crops, every pesticide and herbicide operator need to qualify and adhere to the relevant regulations as published in the Fertilizers, Farm Feeds, Agricultural Remedies and Stock Remedies Act, 1947 (Act No. 36 of 1947) by the Department of Land Reform and Rural Development (DALRRD).

Prior to applying at SACAA, aspiring RPA/UVA operators will be required to obtain aviation training at an Authorised Training Organization (ATO). Previous experience is recognised by SACAA for a person who has held a pilot license; a military qualification equivalent to a license and rating; an air traffic control license or a military qualification equivalent to an air traffic control license or previous commercial air unmanned aircraft operations experience.

SACAA approved training organisations are permitted to offer RPA/UVA training courses.

Orchard and tree needs are unique

A recent international survey confirmed that progress in sensor miniaturisation is increasing the global popularity of unmanned aerial vehicle-based remote sensing applications in many domains of agriculture. “Fruit orchards as the source of the fruit industry chain require site-specific or even individual-tree-specific management throughout the growing season – from flowering, fruitlet development, ripening and harvest – to tree dormancy.”

An increase in research on deploying UAVs in orchard management has yielded new insights. “Challenges relating to determining the optimal approach (e.g., image-processing methods) are hampering widespread adoption, largely because there is no standard workflow for the application of UAVs in orchard management.”

Agri drones with payload capacity varying from 4 litre to 70 litre are adding convenience to crop, orchard or vineyard spray management. The drones are easy to handle and convenient to move from one site or farm to another.

Due to its programming, agri drones are full or semi-automatic as they fly out and return to the original base after spraying trees in the orchard. Precision engineering ensures the latest and future spray drone models are optimally wind proof, rain proof and dust proof with a high anti-interference ability.

Researchers are convinced that precision technology is a dynamic partner to be included in a horticultural production plan. However, technology is developing at such a rate that farmers need to clearly distinguish between the pros and cons of a professional spraying drone as an asset, compared to using it as a contracted service only.

Agriculture spraying drones can replace high boom pesticide or herbicide sprayers. Remote-control copters are also increasingly used for fertilisation and to sow seed. To apply granular fertilisers or sow seeds the spray tank is replaced, enabling applicators to multitask.

Doing a better job

According to experienced drone pilots and registered spray operators, drone spraying is a cheaper option. “It is also doing a significantly better job than traditional aircraft as they fly slower and lower, are GPS-controlled and can follow 3D terrain models for more precise and drift-resistant spraying,” says Wise.

According to Wise the current average cost for crop spraying using a fixed-wing aircraft is “pegged at between R400/ha and R500/ha, compared to the DJI Agras T30 drone costs at R250/ha to R400/ha.” 

Gerhard Mulder, a farmer at Tolbos Estate near Napier, says the elimination of a tractor in the spraying process in orchards or in the field makes for higher density planting which could increase yields per hectare.

“Spraying from the top with the drone will ensure optimum accuracy into the heads of crops, it will save up to 70% of hours usually taken up by tractor related spraying. In the long run farmers could save on tractor replacement too,” says Mulder.

Wise confirms that spraying accuracy is better than with aerial application “since drone calibration and GPS controlled systems allow for persistent predetermined flight lines for centimetre precision. With the spray nozzles being directly under the propellers as the driving force, efficacy of contact insecticides or pesticides will benefit from enhanced penetration.”

Weighing the options

Should farmers consider purchasing a drone for own, shared or contractual services with one or more licensed operators, a new 30-litre payload will cost about R350 000 which include training and support, says Wise. Previously used drones are also available.

With the market valuation retailing value of the drone in mind, some owners would prefer to take out asset finance. In that case, drone insurance will be required to assist them with cover, should the drone be damaged, stolen or cause damage. An insurance house pointed out that accidents do happen. “Third-party liability insurance will be needed to cover losses potentially caused by the drone.”

Other key considerations are accuracy and penetration, professional training, after-sales support, the drone’s ability to offer more night spraying hours and the benefit of short notice availability by drone spraying contractors, saving money should a pest or weed crisis arise.

Producers need to note that all applications for relevant licensing must be submitted to the SACAA for company, drone and operator registration. Pest Control operator certifications are done by DALRRD, as is the case with arial, mechanical or hand crop spraying in South Africa.

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