Application Rate Accuracy and Distribution Uniformity of Cover Crop Seeding with an Unmanned Aerial System (UAS)

Highlights The measured flow rate differed from the flow rate determined by the manufacturer-recommended calibration. The under-application ranged from 9.5% to 17.7% for cereal rye applied with UAS across different rates and flight speeds. The single-pass patterns showed skewness with more material deposition towards the left of the swath. The one-direction application method showed improved distribution uniformity compared to the progressive application. Abstract. The use of unmanned aerial systems (UAS) for seeding cover crops is increasing rapidly, whereas limited information exists on their application performance. Therefore, studies were conducted to assess the application rate (metering) accuracy and distribution uniformity of cover crop seed (cereal rye) applied with a UAS (DJI Agras T25). Static tests were conducted to determine the actual material flow rate from the hopper at different metering (hopper) gate openings. Field tests were conducted to determine the applied rate and to assess the uniformity of cereal rye distribution across the swath at different target rates and flight speeds. The actual flow rate (kg min -1 ) differed from the values suggested by the internal calibration, resulting in a significant underapplication of cereal rye (9.5%–17.7%) across different target rates and flight speeds during the field tests. The single-pass spread patterns showed leftward skewness, indicating greater material distribution (51% to 64%) towards the left and less material deposited (29% to 40%) towards the right. The simulated overlap spread pattern analysis indicated no effect of application rate or flight speed on the distribution uniformity of cereal rye. However, the one-direction application method exhibited improved material deposition within the swath compared to the progressive method. A CV analysis at different simulated effective swaths indicated no considerable improvement in the distribution uniformity at narrower operating swaths. Future research should investigate the effect of other operational parameters, such as application height and spinner-disc speed, on effective swath and uniformity, along with testing different cover crop seeds (mixtures). Keywords: Application rate, Cover crop, Distribution uniformity, Effective swath, Flight speed, Metering accuracy, Unmanned aerial systems.