Better Droplet Deposition and Internode Shortening Effects of Plant Growth Regulator EDAH on Maize Applied by Small Unmanned Aerial Vehicle Than Electric Knapsack Sprayer

Maize (Zea mays L.) lodging is an important factor limiting its yield increase worldwide. EDAH (containing 27% ethephon and 3% DA-6) is commonly used to decrease lodging. There is an urgent need to select efficient application methods of agrochemical for better spray deposition. In our research, an unmanned aerial vehicle (UAV) (15 L ha(-1) and 30 L ha(-1)) with EDAH dosages of 72 and 90 g a.i. ha(-1), and electric knapsack sprayers (EKS) (450 L ha(-1)) with dosages of 90 g a.i. ha(-1) were used to compare the droplet deposition distribution, uniformity and maize growth. According to our research, EDAH applied by UAV had a higher droplet deposition rate than EKS; EKS had a higher droplet coverage rate, deposition density, droplet distribution uniformity. At the same dosage of EDAH, the UAV had a better effect on controlling maize growth than EKS, and almost equal effects were detected when the dosage applied by the UAVs was decreased by 20%. Considering the lodging occurrence and yield, we recommend that the dosage of EDAH applied by UAVs should be 72 g a.i. ha(-1) when there is weak lodging and 90 g a.i. ha(-1) when there is heavy lodging, with a spray volume of 15 L ha(-1).