Agronomy and Horticulture, Department of


First Advisor

Greg R. Kruger

Date of this Version



A THESIS Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Science, Major: Agronomy, Under the Supervision of Professor Greg R. Kruger. Lincoln, Nebraska : August, 2018.

Copyright (c) 2018 Andre de Oliveira Rodrigues


One of the largest challenges in agriculture is weed management. Improper or sub-optimal application techniques can cause decreased weed control and increased environmental contamination. Effective weed management is highly correlated with the product and the application method. Herbicide performance are affected by environmental conditions; they influence the physiology and growth of a plant and as well the herbicide performance. Among all environmental factors, rain shortly after herbicide application is one of the most harmful issues to the performance of the herbicide. Droplet size is a key factor in pesticide applications in regards to both drift and efficacy. Droplet size can be altered by several application parameters, such as the nozzle type, pressure, orifice size and spray solution. Droplet size is a key component in pesticide application with respect to overall application efficacy and off-target movement. As tank mix ingredients can significantly influence the resulting droplet size, agitation systems are critical to ensuring proper mixing of all components and overall performance. Sitting time, a period where the tank is held in a non-agitated state, potentially affects droplet size as well.

The objectives of this research were: 1) understand the influence of nozzle spacing, boom height, nozzle type, on weed control, also expand the scientific knowledge on aforementioned parameters. 2) Evaluate the effect of rainfall after herbicide application on weed control, following certain intervals in order to understand the wash off effect. 3) Analyze the impact of nozzle type, application speed and pressure on weed control, in order to contribute to a more reliable recommendation of such parameters.

This research highlights the impact of parameters regulated by the sprayer on weed control and allow a better understanding of how non-chemical parameters affect the efficacy on weed management, as well as a greater understanding on absorption and evaporation of herbicide plus losses of application efficacy. The results will clarify some of the most concerning question on one of the most complex process in agriculture.

Adviser: Greg R. Kruger