Drones conquer horticulture

Until a few years ago, drones were boys’ toys, or they were used for military and photographic purposes. Recently, applications are being developed to use them in the agricultural sector. There are numerous possibilities, even within greenhouses. Here you will find an overview.

Diseases and conditions within greenhouses
Greenhouses are enormous, and it is difficult for the grower to check the health of thousands of plants. Currently, 5 to 25% of plants go to waste because of diseases, bacteria, fungi, damage, and other causes. That is why students at the InHolland College for Aeronautical Engineering in Delft, the Netherlands, are working on a drone that can fly inside greenhouses and analyse the plants. The students explain: „With the naked eye, you can only see the effects of plant diseases after three days, but by then it’s too late. Within that time frame, diseases can spread.”

Diseased plants show changes in the infrared spectrum within a few hours’ time. With an infrared camera, a drone will be able to check a whole greenhouse rapidly. Furthermore, drones can carry sensors that measure the climate around the plant: humidity, brightness, temperature, and CO2-levels. All data is analysed by special software. The students are using technology that was developed by NASA for satellites which observe Earth.

Greenhouse cover damage detection
In practice, damage to the cover of a greenhouse due to a storm or whirlwind is not easy to detect. It is hard to count the broken windows, especially when a greenhouse is filled with crops. Soon, this will all become easier. Insurance company Achmea and damage specialist PinC Agro are researching the possibility of detecting damage from the air. The first tests using a drone have been promising. They are now working on a camera that will not only spot broken windows but will also be able to detect cracked panes.

Crop growth from the air
It is quite possible to monitor plant growth from the air. Three companies in the Netherlands and Belgium jointly offer a drone service for this. AkkerAnalyse from Marknesse (the Netherlands), contractor Thijssen from Nieuwehorne (the Netherlands) and Aurea Imaging from Zaventem (Belgium) each owns an eBee Ag UAV. Each drone is equipped with four different cameras, including a multispectral camera that measures leaf surface area and crop development. On request, a thermal camera can be added to detect drought stress, diseases, viruses, and fungi. The data are processed by Agrifirm Plant and converted into a plan of action to fertilise or spray specific locations. The companies mainly focus on agricultural applications. The price is between €15 and €25 per hectare, depending on the total area.

Spraying of plots
A Chinese company has developed a drone that can spray agricultural plots. They can complete 4 hectares within an hour. The drone carries a spray tank of almost 10 litres. The device is kept in the air by eight rotors. Although the drone can spray 4 hectares within an hour, it must land a few times to recharge the battery. On one battery, the drone can only fly 12 minutes.

The name of the spray drone is Agras MG-1 and was developed by the manufacturer DJI, the market leader in drones and camera drones. In China and South Korea, these drones are already widely used. In the Netherlands, this application is still prohibited. In Germany, however, they are allowed, in particular for spraying vineyards on mountain slopes.

This movie demonstrates how the Agras MG works.

Delivery of ordered goods
In Alaska, Amazon is experimenting with drone deliveries. Alongside this, horticultural supplier Royal Brinkman from the town of ’s Gravenzande in the Netherlands trialed drone deliveries within the Westland area last year. „Due to legal and regulatory limitations, this won’t become an everyday occurrence just yet”, a spokesperson said. „We’ve looked into the possibilities and continue to follow the developments closely.”

This movie shows how a drone delivers an order at Beyond Chrysant in Hoek van Holland.

Pollination of flowers
The Robobee is a mini drone as big as a bee, that will be able to pollinate flowers in areas where bees have disappeared due to epidemics. The drone with a wingspan of 3 cm and a weight of 80 milligrams, has been developed by Harvard University. The tiny wings flap 120 times per second. It will be at least 20 years before these drones can be used to pollinate flowers. According to the researchers, it will not offer a sensible solution to the problem of bee mortality. It is much better to prevent bee mortality in the first place.