For precision farmers this really does close the virtuous circle. UAVs can scan the crop, identify and map problem areas and then return with targeted applications of pesticides or nutrients to rectify any deficiencies or treat the disease or pests.
UAV’s size and small low payloads limiting factor
Like spray applications, the limiting factor for fertiliser applications is the UAV’s size and small low payloads. This total weight in the USA, for example is restricted to less than 55lb (25kg) before tougher rules apply.
Nevertheless, this still provides plenty of scope for applying macro- and micro-nutrients, explains Bill Reynolds, CEO and Chief Pilot at Leading Edge Aerial Technologies, based in North Carolina in the USA.
“Operating a single UAV is proving to be a suitable way to apply precision applications in locations that are difficult, unsafe or inaccessible to manned aircraft. Indeed, with our application software, we can also identify areas missed by an aerial application and fill in the gaps.
“Application rates are the most important factor that influences the area that can be treated in a day. We find a reasonable rate is between 5-10lbs/acre (5.6-11.2kg/ha), which during the past two years has allowed us to cover 250 acres (101ha) in a day with dry materials,” he says.
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Prescription mapping is key
Prescription mapping is the key to using the UAV, he comments. “Initial crop scouting with an UAV with NDVI sensors to perform crop health surveillance is followed by generating the prescription map,” he says. “Loading the map and flight plan onto the UAV is important for the successful integration for agricultural use. We are using this workflow every day around the Country, and we have developed a number of other workflows that are really helping aerial applicators.”
PrecisionVision 35X UAS
Out in the field Leading Edge Aerial Technologies’ clients apply nutrients with the PrecisionVision 35X UAS, which is designed (software and hardware) and built by the company in the USA. This can used for liquids, granules and ultrafine applications. It has a built-in variable rate controller as well as software for autonomous operation.
Software also adjusts the applicator’s flowgate setting and swath width to match the desired application rate. For an application rate of 5lb/acre (5.6kg/ha), for example, it requires a flowrate of about 10lbs/min (4.5kg/min) this equates to covering about 2 acres/min (0.8ha/min).
It’s important to remember these are precise, targeted treatments to small areas of the crop
“With our PrecisionVision 35X UAS this rate would normally require about two and half minutes for the application of the hopper load. But we have engineered the software to enable us to return and relaunch in about one and half minutes. This way we can easily cover up to 250 acres (101ha) in a day. Also, it’s important to remember these are precise, targeted treatments to small areas of the crop,” Bill explains.
