Precision FarmingManaging the field with drones

Tech­ni­cally they are called Unmanned Aerial Vehi­cles (UAVs) or Remotely Piloted Aircraft (RPA), but users commonly refer to them as “drones”. And they have proven to be a formi­dable tool in the field of preci­sion farming. Drones are able to provide highly signif­i­cant data on the state of crops, which was unat­tain­able until recently. They are now commonly used to monitor crop vigour, health status and to detect water stress. However, their use for spraying is not yet widely utilised, though it is grad­u­ally gaining ground.

Pedro Lucas is CEO of Niufly, a company that specialises in drone spraying, and says there are signif­i­cant advan­tages. “Drones do not compact the soil, they adapt to any soil profile, they can work on steep or gentle slopes, they move faster across the field, and they can better match the treat­ment dose to the needs of the crop because the appli­ca­tions are low volume.”

Advan­tages of spraying with drones

Other advan­tages are that drones can easily reach areas that are diffi­cult to access, like very muddy plots where machinery could get stuck, and water­logged crops like rice. The oper­ator is also less at risk from the chem­i­cals being applied. From an envi­ron­mental point of view, battery-powered drones do not emit pollu­tants during oper­a­tion, which is another advan­tage over machines powered by combus­tion engines.

But drift, in which the droplets move through the air and do not reach their target, is more contro­ver­sial. A study carried out by the Univer­sity of Seville in inten­sive olive groves found that spraying with a drone produced less drift than using a conven­tional sprayer. However, other studies have shown that drift can be the same or greater with drones. “To avoid drift, it’s essen­tial to set up the drone correctly and to only spray in the right envi­ron­mental condi­tions,” says Pedro.

Chal­lenges and constraints

The main problem with drone spraying is the restric­tion imposed by Euro­pean regu­la­tions. Since 2009, aerial spraying has been banned in the EU. However, there are a few excep­tions with special permits. In addi­tion, the Euro­pean Commis­sion has set a target to halve the use of chem­ical pesti­cides by 2030.

To resolve this situ­a­tion, there is talk of the need for a new law that regu­lates drone treat­ments more specif­i­cally, as the current regu­la­tion was made with aerial treat­ments carried out by planes and heli­copters in mind. Although phytosan­i­tary treat­ments with drones are very restricted and require special permits, other prod­ucts can be more easily applied.

“We apply solid prod­ucts like gran­u­lated fertiliser and biolog­ical control agents, which are approved, as well as liquid prod­ucts like diluted fertilisers, bios­tim­u­lants, bio-insec­ti­cides and bio-fungi­cides, which are not clas­si­fied as phytosan­i­tary prod­ucts,” says Pedro. In terms of phytosan­i­tary prod­ucts with specific autho­ri­sa­tions, Pedro has carried out autho­rised treat­ments against rice blight and fruit flies with prod­ucts that can be applied from the air.

Key aspects

To see how spraying by drone is done, we trav­elled to an orange grove in Valencia to be treated with a bios­tim­u­lant. According to David Blanco, Niufly’s tech­nical oper­a­tions manager, it is essen­tial to have an accu­rate diag­nosis and analysis of the plots to be treated so that the spraying can be carried out correctly. “We always digi­tise the plot with RTK, analyse the data thor­oughly to define the treat­ment, and then configure the task correctly so the drone works auto­mat­i­cally,” he explains.

“First we do a remote sensing flight at an alti­tude of 80-120m. We use drones equipped with thermal, multi-spec­tral and RGB sensors to assess the crop as accu­rately as possible, and use the data to decide which areas to spray and what dose to apply.” In a single day they can assess up to 300ha. They also collect leaf and soil samples, the analysis of which comple­ments the remote sensing data and allows the devel­op­ment of more accu­rate algo­rithms for pest and disease inci­dence. Once the task has been config­ured, the drones will be flown for spraying.

We use four-propeller drones with an eight-litre tank,” says David. “This gives us of six to eight minutes of autonomous effec­tive spraying, allowing us to spray up to 60ha per day. In the two treat­ments we have carried out with autho­rised pesti­cides the dose has been 8 litres/ha.”

Woody and herba­ceous crops are culti­vated in completely different ways. In woody crops the planting line must be respected while in herba­ceous crops a uniform appli­ca­tion over the entire area must be achieved. In Pedro’s expe­ri­ence, early growth stages are ideal for drone treat­ments, because of the lower leaf mass. It is here that the highest effi­ciency is achieved, as long as the other vari­ables (height, speed, applied volume and droplet size) are also correct.

Closing the cycle

One thing Niufly has pioneered is the aerial release of biolog­ical control agents, although tech­ni­cally this is not consid­ered spraying as it is a solid product being applied. In order to distribute these ‘good bugs’, which help in the fight against pests and diseases, they have modi­fied the drones to allow for controlled release, ensuring proper distri­b­u­tion where needed.

Regard­less of whether a liquid or solid product is applied, correct main­te­nance of the drones after treat­ment is vital. The gears, pumps, connec­tors, and every­thing else has to be cleaned so that the drone is in the best possible condi­tion for the next treat­ment.

To ensure the effi­cacy of the treat­ment, a thor­ough and detailed follow-up should be carried out after­wards. This is done with remote sensing flights and by increasing the number of samples taken in the field. In this way, Pedro and David can reassess the health status of the crop and obtain agro­nomic insights, producing small and large-scale maps of crop vigour or produc­tion fore­casts.