Agronomy and Horticulture, Department of


First Advisor

Greg R. Kruger

Date of this Version

Summer 7-30-2020


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: June, 2020

Copyright 2020 Milos Zaric


Availability of dicamba-tolerant (DT) crops from 2017 provided farmers with additional herbicides for weed control management in row crops. However, the technology alike this one has concerns regarding dicamba off-target movement (OTM) causing undesirable effects on sensitive vegetation. Even though dicamba has high water solubility OTM that has often been overlooked when it comes to unintended crop exposure is dicamba tank contamination. Considering the complexity of spraying equipment soybean response may be expected even when small amounts of residues are left in the spray equipment. Typically, the same field spray equipment is used to perform herbicide application through growing season there is a limited knowledge how various postemergence (POST) programs impacts soybean response when found in scenario with dicamba tank contamination and requires additional research.

Furthermore, as one way to mitigate OTM potential release of DT crops was followed with registration of various agents also known as drift-reducing agents (DRAs). Increased awareness of both growers and commercial applicators to reduce unintended adjacent crops injury use of labeled DRAs in combination with drift-reduction nozzles represent common practice. Exposure of sensitive crops to sublethal doses of dicamba has been well documented over several years; however, there is limited information available how combination with commonly used DRA’s may impact application process and weed control. Considering limitations on available literature the main objective of this research were: 1) evaluate response of non-DT soybean variety when exposed to commonly applied POST herbicide program in combination without or with dicamba as tank-contaminant and 2) evaluate impact of DRAs on weed control in response to dicamba applications. The results of this research expanded knowledge and will help in education in the future management decisions about potential implications associated with common mitigation techniques used with dicamba application as well as helped with understanding how various POST herbicide program affect soybean response.

Advisor: Greg R. Kruger