Drones in citrus groves

Drones are becoming increas­ingly impor­tant in many areas of agri­cul­ture, not only in arable crops but also fruit produc­tion and viti­cul­ture. In Sicily, the company Pheromed Fly, which has offered drone services since 2015, has seen signif­i­cant growth in requests from farms that have decided to use these tools as a support for agro­nomic manage­ment.

“Up until a few years ago we were only working with farms on an an exper­i­mental level” explains owner Giovanni Petrilig­gieri. “Today, we have fully entered the agri­cul­tural sector, which comprises about 30% of our busi­ness.” Mr Petrilig­gieri has dedi­cated himself to research, working with insti­tutes and univer­si­ties to test the useful­ness of surveilling crops using these tools, in compar­ison with tradi­tional visual checks performed by agri­cul­tural tech­ni­cians.

The advan­tage of flying

“It is much less effec­tive to check crops on the ground plant by plant, compared to from the air, which provides a much wider and more compre­hen­sive view,” he says. “And above all, it allows the use of high-preci­sion detec­tion tools.” The drones used at the farm are more than a meter across, and come equipped with multi­spec­tral and digital cameras which collect high defi­n­i­tion images in flight, above 45 Mpx, to obtain precise and complete plot mapping.

The data collected by the drone is then analysed by the farm.

“The use of multi­spec­tral cameras, which have five different colour bands, allows to calcu­late the vege­ta­tion indices based on the percentage of radi­a­tion reflected in the various specific bands.” The most common vege­ta­tion index, Normalised Differ­ence Vege­ta­tion Index (NDVI), eval­u­ates the pres­ence of photo­syn­thetic activity, comparing the red spec­trum, in which the chloro­phyll is absorbed, with the nearby infrared spec­trum, in which the leaves reflect light to prevent over­heating.

All crops

“Living in Sicily, we started with citrus trees, which repre­sent our largest crop,” continues Mr Petrilig­gieri. “With the Univer­sity we under­took various exper­i­ments in different areas of Italy on vines, pome­granate, kiwi, and fruit trees, as well as wheat and rice. The data collected is always georef­er­enced, it is the inter­pre­ta­tion that changes.

Moni­toring from the air is much more effi­cient than moni­toring from the ground, where each indi­vidual plant is checked.

Giovanni Petrilig­gieri

This is one of the farm’s orange orchards, which are moni­tored annu­ally by drones.

Once all the data has been collected by the drone, it must be inter­preted. Only then can correc­tive measures be taken. This is done by the farm’s agron­o­mist who, based on personal expe­ri­ence, makes the best deci­sions to return the crop to its optimal condi­tion. “The use of the drone makes addi­tional func­tions possible, like being able to photo­graph the farm from above, obtaining precise mapping of the fields.” This allows impor­tant deci­sion-making infor­ma­tion to be gath­ered prior to preparing irri­ga­tion systems, pruning or simply to help under­stand the produc­tive poten­tial of the ground.

A perfectly controlled orange grove

Another farm that is using drones as a strategic busi­ness tool is Bioa­gri­cola F.lli Solarino in Rosolini, in the province of Syra­cuse. Here, the 30ha of organic orange groves have been constantly moni­tored since 2017 using drone mapping. The farm’s most impor­tant crops are various vari­eties of yellow pulp oranges, which are exported all over Europe.

The evolu­tion of tech­nology helps us to avoid the use of pesti­cides.

Monica Solarino

Monica Solarino, CEO of Bioa­gri­cola F.lli Solarino in Sicily

“Our farm can be consid­ered an organic pioneer,” explains CEO Monica Solarino. “We started in 1996 when there was still a lot of scep­ti­cism about this type of farming, but we believed in it and grad­u­ally made full use of all the possi­bil­i­ties offered by the evolu­tion of tech­nology to avoid the use of pesti­cides.”

The orange groves are perfectly kept. The plant­ings are never more than 30 years old and are renewed regu­larly to be strong, healthy, produc­tive plants. The genetic variety has been increas­ingly evolved to cope with climatic stress in an organic system. During the hottest and driest months, irri­ga­tion is used with under­ground systems that not only save water, but also reduce the pres­ence of surface weeds, reducing the need for of mechan­ical weeding.

What made it possible for the farm to make a real qual­i­ta­tive leap was the use of drones for crop moni­toring. Since then, Bioa­gri­cola F.lli Solarino has increased produc­tion by at least 20%, reduced waste, and above all, has signif­i­cantly improved the quality of the oranges it produces.

Between flow­ering and harvesting

“In the exper­i­mental phase we performed two flights a month,” says Ms Solarino. “Today we program four to five flights between flow­ering and harvesting. This makes it possible for us to keep the vege­ta­tion and devel­op­ment index of the plants moni­tored, pointing out if and where there are prob­lems or failed areas”.

“When mapping shows areas that are turning yellow, this means that the plant has prob­lems,” she explains. “Based on geolo­cal­i­sa­tion, the tech­ni­cian can go and see what the prob­lems is. Some­times there are plant protec­tion prob­lems, other times there are prob­lems with irri­ga­tion or ferti­ga­tion systems. In either case, this tech­nology has made it possible to improve and signif­i­cantly reduce the use of tech­nical resources.”

Thanks to the drones we can esti­mate the produc­tion in advance and better organise the harvest, grading, pack­aging and ship­ping.

Monica Solarino

Another benefit of using the drone is the capa­bility to esti­mate produc­tion in advance, using the multi­spec­tral camera to see the amount of fruit per hectare as soon as the colour starts changing. “Knowing the plant yield in advance is extremely impor­tant for us, as we can better organise the harvest and all following phases of grading, pack­aging and ship­ping.”

The use of drones makes it possible to perform multi­spec­tral aerial moni­toring, which results in precise and complete georef­er­enced field mapping (Pheromed Fly images).

Sustain­able costs

“Today, the cost for using a drone service is perfectly sustain­able, says Ms Solarino. The advan­tages far outweigh the costs, which gener­ally never exceed €30-40/ha (£26-£35) – savings are made in prod­ucts, irri­ga­tion and labour. In addi­tion, the drone used at this farm has provided an indis­pens­able service, from the design and cali­bra­tion of the subir­ri­ga­tion system based on indi­vidual field terrain, through to deciding whether to replace the orange plant­ings”.

“Thanks to drone mapping, we can choose the right moment to replace plant­ings and make impor­tant choices in extra­or­di­nary situ­a­tions, like the recent Citrus Tris­teza virus attack. Only multi­spec­tral aerial moni­toring is capable of following the evolu­tion of such an attack, simul­ta­ne­ously indi­cating the right path to follow.”