Weed management in early-planted Illinois soybean

Chapter 1 includes a literature review of soybean growth and development, current weed management systems in soybean, characteristics of summer annual weeds affecting their success in current cropping systems, and factors influencing the performance of glyphosate, glufosinate, metribuzin, S-metolachlor, and pyroxasulfone. Soybean yield improvements have been experienced as a result of numerous factors, including but not limited to advancements in genetics, planting methods, seed treatments, pest control, and tile drainage. Three components contribute to soybean yield — pods per node, seeds per pod, and the weight per seed. Extending the growing season by planting soybean earlier enables a higher potential for the number of pods and seeds per plant, thus enhancing yield. Historically, soybean have been planted following corn, however, this practice appears to be reversing albeit slowly. By doing so, the growing season for soybean is lengthened, and soybean emergence and growth stages align with weed emergence differently than before. Therefore, the critical period of weed control in early-planted soybean may shift, along with weed species emergence timings and their importance in control relating to soybean emergence. Waterhemp (Amaranthus tuberculatus) is the primary weed dictating the weed management strategies implemented by growers in many cropping systems across the Midwest. There are many traits of waterhemp that have made it a driver weed, however, the emergence pattern of waterhemp poses the greatest challenge in controlling this weed throughout the whole growing season. Despite this, waterhemp is not an early emerging summer annual weed like giant ragweed (Ambrosia trifida) or common lambsquarters (Chenopodium album). By shifting the planting date of soybeans earlier, these weed species may escape tillage and burndown treatments, thus increasing pressure on preemergence (PRE) herbicides. As a result, investigating PRE rate and timing, along with the impact of a layered soil-residual herbicide with the POST application on season-long weed control and soybean yield, are necessary to understand the interactions between weed interference and soybean growth and development. Chapter 2 describes field experiments conducted at four locations across central Illinois. Field studies were designed to investigate the influence of PRE rate, PRE timing, and the inclusion of a residual herbicide with the POST application on weed control and soybean yield. PRE treatments contained a mixture of S-metolachlor + metribuzin, while POST treatments contained a mix of glyphosate + glufosinate, and certain treatments the inclusion of pyroxasulfone. PRE treatments were applied at half and full rates, and either at planting or approximately two weeks after planting. POST treatments that included pyroxasulfone received either a half or full rate. Field study results indicated that PRE rate had a significant effect on weed control assessments, while PRE timing or the addition of pyroxasulfone to the POST application did not result in a significant difference in level of weed control. Despite this, late-season weed control ratings and soybean yield data were very similar in numerical values and not significantly different for all treatments receiving a PRE + POST. Future research needs to be done to continue evaluating PRE rate performance, and the importance of residual herbicides with the POST application in an early-planted soybean environment. Aside from these factors, soybean plant population, cultivar growth architecture, and the influence of different herbicide active ingredients on weed control, soybean crop injury, and ultimately soybean yield should also be investigated.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Crop Sciences

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2023

Author dc:creator

• Miller, Logan Robert

Contributors dc:contributor

• Hager, Aaron Hager G
• Tranel, Patrick J
• Williams, Martin M

• Weed Management
• Early-planted Soybean
• Layered Residual Herbicide

Statement dc:rights

• Copyright 2023 Logan Miller

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/121533

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F121533