Randy Price, Harrell, Dustin L.
The DJI AGRAS MG-1/1S is a commonly sold spray drone with a 2.5-gallon tank and 10-minute flight time. Because of its small size, the drone’s main use in the U.S. will be for herbicide work on levees, fence rows, hill sides, ravines, swamps, wetlands, right of way easements and horticultural areas. Still, spraying in these areas will require a spray system with low drift qualities as susceptible crops, plants, gardens and other foliage maybe located nearby. Testing with the DJI drone has indicated that high drift rates (greater than 20% of the application rate) can easily occur. For this reason, the LSU AgCenter has been evaluating ways to reduce drift from this drone, and the following recommendations are given as methods to achieve this result while still maintaining a good droplet size for low volume application work of less than 2 gallons per acre (GPA).
The factory XR11001 tips supplied with the drone are known to create more drift than most other nozzle types (see LSU AgCenter publication No. 3632: Nozzle tip selection for drift control). For this reason, several air induction (A.I.) flat fans were chosen for the testing on the drone and are typically better than XRs for drift control. The A.I. flat fans tested on the drone were the Greenleaf AM11001, which matched factory orifice sizes, and the TeeJet AIXR110015 and AIXR11002 nozzles. In all tests, A.I. nozzles greatly reduced drift with the drone by up to 60% over the standard XR11001 nozzles. In individual tests, the AIXR nozzles (both the 110015 and 11002) were too coarse for low volume application work less than 2 GPA. At these low levels, the AM11001 nozzles (0.01 GPM orifice size) had a much better droplet spectrum (Figure 1; Vmd = 301 micrometers [um]) for low-level application rates (2 GPA). For this reason, the Greenleaf AM11001 and similar A.I. flat fans are recommended for use on this drone.
During testing, it was noticed that two sprayer settings can easily cause excessive drift. These two settings are the “efficiency” and “effective” modes, which relate to the percentage of area covered by the drone and the area covered at the fastest spraying speed (15 mph), respectively. Many users are enticed into choosing 100% for this value, thinking they are performing a more “effective” spraying operation. However, they are actually choosing the fastest possible spraying speed (15 mph), which always causes more drift. For this reason, choosing lower efficiency/effective rates (less than 50%) will help reduce drift (Figure 2). Also, the AM11001 air induction flat fans scored better at reducing drift (Figure 2) than the XR11001 nozzle tips.
The effective swath width of the DJI AGRAS MG-1/1S drone is not well known or documented. Multiple passes where flown over a dye pattern test string at 10-, 20- and 28-foot swath widths, and results indicated that the drone had a solid 10-foot swath width. Major skips occurred at the 20- and 28-foot swath widths for both tips. The AM11001 nozzles had a more uniform coverage than the XR11001 nozzles with a C.V. (coefficient of variation) of 0.12 versus 0.22 for the XR11001 nozzles. For this reason, the AM11001 and similar nozzles are recommended for this drone.
Using these recommendations, the DJI MG-1/1S plant protection drone can be setup to have much better drift reduction (up to 60%) and spray qualities over the factory nozzles XR11001 nozzles and should be used in areas where drift reduction is a concern.
Dr. Randy Price is an agricultural engineer the Dean Lee Research and Extension Center in Alexandria, Louisiana, and Dr. Dustin Harrell is a soil and fertility specialist at the H. Rouse Caffey Rice Research Station in Crowley, Louisiana. Both have interest and experience using sprayer drones. If you have any questions or comments, please contact these specialists by phone or email via the contact information provided at the LSU AgCenter website, www.lsuagcenter.com.