Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/10/2008
Publication Date: 12/5/2008
Citation: Zhu, H., Brazee, R.D., Fox, R.D., Derksen, R.C., Ozkan, H.E. 2008. Development of a Canopy Opener to Improve Spray Deposition and Coverage Inside Soybean Canopies -- Part 1: Mathematical Models to Assist Opener Development. Transactions of the ASABE. 51(6):1905-1912.
Interpretive Summary: Asian soybean rust can cause great soybean yield loss if it is not treated with proper spray equipment at the right time. Prevention and control of soybean rust requires fungicide applications in the lower parts of the soybean where rust infection begins. Penetration of spray droplets into the lower parts of the soybean canopy using a conventional boom sprayer is difficult, especially under dense canopy conditions. Use of a simple conduit pipe to open the top of soybean canopies was postulated for this research. The opener would be mounted ahead of the nozzles on a conventional boom sprayer, pushing the top part of the canopy forward and permitting spray to penetrate lower parts of the plants. Mathematical models were developed to help optimize placement of the device such that the best possible spray penetration and coverage could be achieved with least damage to the crop. With insight from the models, development of the new sprayer was simplified with fewer errors.
Technical Abstract: A mechanical device, ‘canopy opener’, has been used to bend the top of soybean plants, creating an opening for spraying pest control agents into the lower part of the crop canopy. It follows that there should be an optimum design and placement of the ‘canopy opener’ device that will produce the best possible spray penetration and coverage and least amount of damage to the crop. Mathematical models were developed to assist the development of a canopy opener that would optimize spray penetration into soybean plants. With the introduction of an incomplete elliptic integral of the second kind, it was possible with the models to establish relationships among plant maximal deflection, opener depth inside canopies, and plant height. The models also included determination of opener width by calculating plant recovery motion at different times after release from the opener and the time available for droplets to travel from the nozzle orifice to the target areas inside canopies. Natural frequencies and damping coefficients of soybean plants were determined with a bending beam load cell and a digital video camcorder. The models predicted that for XR8004 nozzles at 276 kPa the optimal opener depth would be 0.14 m and the opener width should be ranged from 0.04 to 0.47 m for the 1.06 m soybean plants. Experimental measurement of maximal deflection and plant motion time agreed with the mathematical models.