Effects of row spacing and nozzle type on spray penetration inside soybean canopy under various wind velocities

Authors: CASTILHO THEODORO, JOSE - The Ohio State University; Zhu, Heping; Jeon, Hongyoung; OZKAN, ERDAL - The Ohio State University

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/14/2026
Publication Date: 5/19/2026
Citation: Castilho Theodoro, J.G., Zhu, H., Jeon, H., Ozkan, E. 2026. Effects of row spacing and nozzle type on spray penetration inside soybean canopy under various wind velocities. Agronomy Journal. 16. Article 997. https://doi.org/10.3390/agronomy16100997.
DOI: https://doi.org/10.3390/agronomy16100997

Interpretive Summary: Suitable spray deposition in the lower soybean canopy is important to control pest and disease effectively. This study tackles improving spray penetration by testing four nozzle types across a range of droplet sizes, wind speeds, and two common row spacings in a controlled wind tunnel environment. The study results show that spray consistently accumulated at the top of the canopy, with sharply reduced deposition in the middle and lower layers. Neither wider row spacing, nozzle selection, nor increased wind speed produced meaningful improvements in penetration to these deeper canopy zones. Although some small gains on spray penetration were achieved by widening soybean rows, their values may diminish in late-season conditions when dense soybean foliage and higher winds restrict spray penetration. Overall, the findings highlight a persistent challenge in soybean production that even with adjustments to equipment and spacing, achieving effective spray delivery to the lower canopy remains limited, suggesting that alternative strategies or technologies may be needed to improve protection where it is most difficult to reach. This study provides important insights for U.S. farmers to increase their income by protecting their soybean from diseases and pests by increasing pesticide delivery to lower soybean canopy.

Technical Abstract: Adequate spray deposition and penetration of pesticides into the lower part of the soybean canopy can increase the chances of successfully protecting plants from diseases and insects. The research was conducted to evaluate the effect of increasing the distance between soybean rows on the spray coverage and deposition of different droplet size classes from various nozzles, delivering spray to the lower canopy in a wind tunnel. Four commercially available spray nozzles with droplet size classification from medium to extremely coarse were mounted on a spray boom with a spray controller to spray an application rate of 150 L ha-1 under laminar wind speeds of 0, 2.4, and 5.1 m s-1. Rectangular pots containing fully-grown soybeans were placed in the test section of the tunnel at center-to-center distances of 0.38 and 0.76 m to replicate narrow and wide row spacings, respectively, commonly used by soybean growers. Eight points in each soybean row were selected to collect spray deposition and coverage with water-sensitive papers (WSP) and acrylic plates (AP), respectively, at the top, middle, and lower layers of the canopy. Results showed that the top of the soybean canopy consistently received the highest amount of spray, regardless of application conditions, as expected, while the middle and lower layers of the canopy did not receive much spray. In addition, row spacing, nozzle types, and wind speeds were not significant factors in increasing spray penetration into the middle to lower layers of soybean plants. The main conclusions derived from this study indicate that while wider row spacing configurations can enhance spray penetration into the lower parts of the soybean canopy, their effectiveness may be limited during late-season applications due to denser canopy conditions and the effects of high wind speeds.