Spray Deposition and Distribution on Rice as Affected by a Boom Sprayer with a Canopy-Opening Device

In China, rice growers predominantly use boom sprayers. However, boom sprayers have several drawbacks related to poor penetration in the middle and late stages of rice growth. Several studies have shown that the use of the canopy-opening device can improve droplet deposition in the middle and under layers of rice. Some growers doubt the efficacy of canopy-opening boom sprayers, whereas others have questions about their use. This study aimed to address both doubts and questions by evaluating the effect of spraying rice using a canopy-opening device and a canopy-opening divider combination device. The tested rice variety was “Longliangyou 2010”. Three different boom sprayers were evaluated for this purpose: (1) a boom sprayer with a canopy-opening device, (2) a boom sprayer with a canopy-opening divider combination device, and (3) a traditional boom sprayer. The effects of the position of the canopy-opening device and the spraying velocity on the deposition of droplets were considered. The experiments showed that the droplet coverage was significantly affected by boom sprayers, the position of the canopy-opening device, the spraying velocity, and the interaction of the position of the canopy-opening device and the spraying velocity. Under the spraying distance of 60 cm from the rice root and the spraying velocity of 1.2 m s−1, the spraying coverage of the paraxial surface of the whole canopy was higher than that of other treatment conditions when the canopy opening device was used. The positive spraying coverage rates of the upper, middle and lower layers were 95.18%, 88.41% and 94.99%, respectively. Compared with the traditional boom sprayer, the use of the canopy-opening device increased the average droplet coverage on the adaxial surface canopy by more than 72.91% and the average droplet coverage on the abaxial surface canopy by more than 6.88%.