Battle for the Belt: Season 3, Episode 4: Ultra – Early Soybean Planting & Weed Control

Season 3, Episode 4 of Battle for the Belt is now available:  https://www.youtube.com/watch?v=nDs6iQhBe7s

In Episode 4 of Battle for the Belt, learn about a soybean planting date and weed control study from Lucas Dias Mendonca, a MS student in Horticulture and Crop Science, conducted at the Western Agricultural Research Station.

At the beginning of the field season, there are many tasks to accomplish before and just after planting. When considering ultra-early planting (prior to April 15), one management practice that needs careful consideration is weed control. In ultra-early planting situations, we often see a reduction in soybean plant population and slow canopy closure due to cold soil and air temperatures, resulting in more competition from weeds. Weeds, such as giant ragweed, can grow more quickly than soybean, especially when the weather is wet and cold (Figure 1)., competing for sunlight, water, and nutrients. Another concern is the influence on pre-emergence herbicide efficacy. Early applications in cold, wet conditions could lead to inconsistent weed control or crop injury from soil applied residual products.

Lucas’ research project compares various herbicide programs for weed control and yield implications in ultra-early planted soybean. In this study, there are two planting dates, “ultra-early” and “normal” occurring in late March/early April and mid-May, respectively. There are six herbicide treatments (Table 1). This research takes place in two fields at the Western Agricultural Research Station, one with a Crosby soil type and the other with a Kokomo soil type, to evaluate potential soil interactions. The target weeds for control in this study are giant ragweed and annual grasses, primarily yellow and giant foxtail.

Table1. Herbicide program treatments for the 2025 growing season. (In 2024, dicamba was used instead of 2,4-D.)

Preliminary results from the 2024 growing season indicate that we cannot rely on pre-emergence herbicides for season-long weed control. Multiple POST applications were necessary to provide weed control in the ultra-early plating date. Applying a residual with the POST improves weed control. For the ultra-early planted soybean, the weed control program that resulted in the highest soybean yield was an early POST application of dicamba + glyphosate followed by a late POST application of glufosinate + glyphosate + s-metolachlor. For the normal planting date, high soybean yields was achieved across several weed control programs.

We are repeating this study for the 2025 growing season, with the first planting date on April 14^th and application of pre-emergence herbicide on April 17^th (Figure 2). Final results from this study will be available in 2026! This study is funded by the Ohio Soybean Council.

Field Updates

The northwest location was able to plant the second planting date of Battle for the Belt last week! The soil dried down enough to plant and average soil temperatures were in the mid-40s (Table 2). Corn and soybean planted on the first planting date (March 27) have not yet emerged, as the temperatures have not been warm enough (Table 3). This location needs about twenty more growing degree days for emergence to occur. Corn and soybean planted on the first planting date (also March 27) at the Wooster location have not emerged yet either. Planting date two occurred on April 18^th with optimal planting conditions! The Western location was able to plant their first planting date on April 18^th (Table 2). Previously, the western location had been too wet to plant, but fortunately had optimum soil conditions for planting last week.

Table 2. Average soil temperature and air temperature for planting date two at the Northwest Agricultural Research Station and Wooster Campus and planting date one at the Western Agricultural Research Station.

Table 3. Precipitation, soil temperature, average air temperature, and cumulative GDDs at the Northwest Agricultural Research Station and the Wooster Campus. Weather data retrieved from: https://weather.cfaes.osu.edu/.

As a recap, this research project includes five planting date windows, 1) Ultra early = late March to early April; 2) Early = mid to late April; 3) Normal = early to mid-May; 4) Late = late May-first week of June; and 5) Very late = mid to late June.

Keep following the ‘Battle for the Belt’ this growing season to learn more and get further updates! You can find the full video playlist of Battle for the Belt on the Ohio State Agronomy YouTube channel.

Authors: Taylor Dill, Laura Lindsey, Osler Ortez, Lucas Diaz Mendonca, Maria Kessler, Diego Mirand Tosta, Alyssa Essman