Drones vs. Ground Sprayers: Acreage and Efficiency Comparison

Drone technology, especially spray drones, has been getting quite popular. DJI, XAG, and other manufacturers have been releasing products with larger capacities and more advanced technologies to improve spraying efficiency while reducing time and costs. 

However, it’s time to stop looking at drone technology as a novelty and dig deeper into its practicality.

While spraying drones have become increasingly popular, not every farmer uses them, and some farmers still prefer ground sprayers. So today, we will be comparing both methods of spraying, their benefits, drawbacks, and where each method is best suited for.

Understanding Ground Spray Systems

To effectively compare these methods, let’s quickly cover how each ground method works.

Tractor-Mounted Boom Sprayer

Tractor-mounted boom sprayers are among the most widely used sprayers globally. This is thanks to their accessibility, affordability, maneuverability, and versatility. You can just attach the sprayer to your tractor, making it easy to integrate it into an existing workflow. 

Tractor-mounted sprayers also offer considerable acreage efficiency, covering up to 60 acres per hour. They also come with large tanks (up to 1000 gallons), meaning you don’t have to keep refilling. 

And for farmers with larger farms, the ROI is quite high since these systems are affordable to run. However, running a tractor-mounted sprayer needs solid ground to prevent rutting or compaction. They are also known to cause mechanical damage to crops.

Trailed Sprayers

If you own expansive, relatively flat farmland, you will appreciate trailed sprayers. It is mounted on the rear of a tractor, often has more capacity than a mounted sprayer, and is easier to maintain. 

However, trailed sprayers are more difficult to maneuver and lack sufficient ground clearance for some crops.

Self-Propelled High-Clearance Sprayers

Self-propelled sprayers are dedicated models that deliver higher speeds, more efficient spraying, and greater clearance for tall crops. 

They are more maneuverable than the tractor-mounted or trailed sprayers and often have higher capacities, but they are also quite expensive to purchase and maintain. 

The risk of rutting, compaction, and crop damage persists with self-propelled sprayers.

Understanding Drones

Sprayer drones are essentially flying sprayers, promising uniform coverage, minimal compaction, and reduced plant damage since they don’t “step” on plants. Drones are practically flying computers, allowing you to customize the drone speed, height, swath, and application rate. 

The application is also guided by GPS, ensuring precise application, and you don’t have to worry about clearance since you can set any height. Spray drones have even been used to spray durian plants, which are typically 65 feet tall or more. Drones can spray up to 25 acres per hour, and their capacities range from 10 litres to 100 litres. 

Let’s also not forget variable spraying, where you can map the field, feed the data into analysis tools, and determine where and how much to spray. By spraying only where needed, close to the plants, and adjusting the spray rate, you can minimize costs and improve ROI compared to traditional methods. 

Drones are also considerably cheaper compared to ground sprayers or airplanes. The use of UAVs is also favorable to the environment since there is a reduction in the use of fossil fuels, though this does not play into the practicality of them on farms. 

Battery Swaps and Refill Bottlenecks

While spray drones seem promising, the realities of drone operations tell a different story. A drone spraying operation involves filling the tank with chemicals, the drone then applies the chemicals according to preset settings, and then the drone returns to the takeoff point for a refill. Now here is where things get complicated. 

The drone’s flight time is usually 20 minutes or less. That means even though the drone has a capacity of 100 liters, it will still have to return to the takeoff point for a battery change every few minutes. The good thing is that these drones come with fast chargers that can charge the battery to full capacity in 10 minutes, but battery swaps introduce significant downtime you don’t need.

Secondly, due to limited flight time, you can’t make the trip too long and will often have to fragment the farm or land in a different location, which introduces additional risks to drone operations. Unlike ground sprayers, drones also need another means of transport to get them to and from the farm. To solve the tank limitation and battery bottleneck, you could deploy several drones. But more drones also means more pilots, which further complicates the logistics compared to ground sprayers, where you only need one operator. Still, if you get the logistics, battery charging, and chemicals mixing processes right, drones can be very useful.

Why Ground Rigs Still Dominate Large Farms

As spry drones become more popular, you’d expect to see them in every farm, but that’s not the case. Currently, for 1000+ acre farms, ground sprayers still dominate due to overall acreage efficiency and ROI.

• Spraying speed – Drones are fast, but not as fast as a self-propelled sprayer. Drones can cover up to 20 acres per hour. Unless drones fix the battery swap and refilling bottleneck, they will never match the speed of ground sprayers, even when you have several drones operating at a time. A standard sprayer with a 36-meter swath and 1000 gallon litre tank can move uninterrupted for a long time, covering 60 to 100 acres per hour. 

• Low refill frequency – As mentioned, drones have a very high refill frequency that introduces downtime. Since ground sprayers have large tanks, the refill frequency is significantly lower, improving the efficiency needed to cover large farms quickly.

• Economies of scale – For large farms, fixed costs of labour, fuel, and logistics are spread across the acres. This makes it possible to afford ground sprayers compared to drones.
• Integration into other farm workflows – A ground sprayer rig can easily be integrated into a farm’s workflow, and it is less limited in the crops it can spray. On the other hand, a spray drone has only one use and can’t be attached to anything else, making it a liability if it’s not used effectively.

Still, ground sprayers struggle with fragmented farms, and saturated or muddy fields may make it difficult for them to enter the farm. As we mentioned earlier, they may also destroy the crops or the soil, making it necessary to find alternatives.

The 20–40 Acre Sweet Spot for Drones

Ground sprayers excel in large farms due to scale and cost structure, but that heavily relies on field design, terrain, and timing. On the other hand, drones have become quite popular for smaller farms, with 20 to 40 acres providing the perfect balance.

For fields of this size, a tractor-mounted sprayer or self-propelled sprayer will be overkill, and economies of scale will not make sense. But for drones, this farm size justifies their deployment. With efficient chemical mixing, optimized battery logistics, and strategically placed refilling tanks, it is possible to run a drone-spraying operation with minimal downtime. 

Drones can effectively reach the edges, turn without needing much radius, and operate at convenient heights without damaging the plants. Drones also don’t need a solid, flat surface, and they will not cause compaction.

Drone Swarming and Future Efficiency

The biggest challenge with spray drones is the limited tank capacity and flight time. But imagine several drones returning for refills and battery swaps, with only one operator behind them. This is called drone swarming, and it could be the future for improving efficiency and ROI in areas where drone technology is currently limited.

Drone swarming refers to deploying a team of synchronized drones over a farm. Instead of relying on a single drone, you can operate several at once, assigning each to a section of the farm. If one drone can cover 20 acres per hour, 3 drones can cover 60 acres, and you will have reduced the amount of labour needed. As autonomy continues to evolve, it will be possible to have drones autonomously charge, refill, and deploy to spray on a farm.

This promises to significantly increase drone spraying efficiency, bridging the gap between drones and ground sprayers. Now it will not be about tank sizes, it will be about how several machines can work together.

Conclusion

The comparison between drones and ground sprayers should not be about which is better. Each technology excels in its own field.

Ground sprayers excel in large farms where throughput matters more.

Drones excel on smaller farms with sensitive crops or where it will be difficult to maneuver with a ground sprayer.

The best approach is not to choose one over the other; rather, integrate both into your spraying workflow.

When evaluating efficiency, it should not be defined by acres per hour; rather, it should be defined by precision per acre, adaptability, and coordination among the different farm machines.