Every growing season provides us with an opportunity for learning, and 2019 was certainly no exception to this rule. Although we need to be cautious about relying too strongly on variety performance from a single year, especially one as unique as the one we have just gone through, there are always agronomic lessons that we can take to heart. In my recent ILSoyAdvisor webinar, I discussed several things that we learned or confirmed in 2019.
Image 1: Single pass post-herbicides on large weeds
are often ineffective.
Proper weed management is critical
With this year’s excessively wet spring, many growers chose to forgo their pre-plant herbicides when fields were finally fit for planting. In most cases, the “pre-plant” herbicide was applied within a few days after planting and was still effective. However, when driving around the countryside, it was easy to identify fields where the first herbicide wasn’t applied until the weeds were too large to control effectively (Image 1).
There were also a few scattered fields where growers seemed to give up on weed control altogether (Image 2). Presumably, in a situation like this, the grower made the decision not to protect a late-planted crop that wasn’t expected to yield well. Although it is understandable to try to reduce inputs in a challenging farm economy, favorable late season conditions allowed many June-planted beans to yield in the 60-bushel range. It is a pretty safe assumption that the yield loss in the pictured field is over 10%. A strong herbicide regimen could have easily been paid for by the yield that would have been gained from effective weed control. A neglected field will also result in weed challenges for many seasons to come.
Image 2: Late-season herbicide was still profitable,
even on June-planted soybeans. The above field did not
benefit from a strong herbicide regimen.
Although earlier planting gives us the best chance to maximize yield, later planting can still yield surprisingly well.
Generally, we see highest yields in soybeans from planting dates around April 20, with a gradual drop-off throughout May. Typically, the yield loss accelerates as we enter June. However, in 2019 we saw less of a difference in yield between early and late planting dates. There were two reasons for this unusual yield response. The first was that conditions were uncharacteristically poor in April and throughout May. This led to severely reduced stands and slow growth of emerged plants. Although seed treatments allowed early plantings to still survive and produce an acceptable crop, untreated seeds planted into these conditions yielded much less (Figure 1). This graph is from a single location but illustrates a wider trend that growers across the state observed in 2019. The second reason for the relatively small yield gap between early and late plantings was the very favorable late season conditions that allowed June-planted soybeans to reach their full potential.
Figure 1: 2019 Soybean Yield Response to Seed Treatment vs. Planting Date
Fungicide applications to soybeans can pay off, even in late plantings.
This year, June-planted beans didn’t encounter much disease pressure. Environmental conditions were not conducive to disease development and very little was observed in fields. Despite this, we did see a significant response to fungicide in our trials (Figure 2). Across three locations and a range of populations, we saw a 5+ bu/A increase in yield with an R3 fungicide application.
Figure 2: Soybean Yield Response to Fungicide in 2019
It is important for growers to remember not to make large changes to their operations based on the results of one year. What made good agronomic sense in 2018 will still make sense in 2020, despite the feeling of maybe waiting too long to plant in 2019 or other rearview mirror analyses. Variety performance results should be taken with a grain of salt since we will most likely not encounter another year exactly like 2019. As outlined above, that doesn’t mean that there was nothing to learn. I would like to reiterate the top three things that I learned or confirmed this past year:
  1. Weed management is essential to produce a high-yielding crop.
  2. If environmental conditions or other circumstances force late planting, don’t give up on the crop.
  3. Fungicide applications can result in a significant return on investment, even in later planted soybeans.

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About the Author: Jason Carr

Former Soy Envoy and current soybean technical product manager with Bayer Crop Science, Jason Carr evaluates new soybean germplasm and assists independent licensees with identifying varieties that fit their operations. Previously, he led agronomic research projects with corn and soybeans focused on creating tailored solutions for growers. Prior to that, he spent a decade in soybean breeding with Monsanto and led a team developing numerous commercially successful varieties in RM groups 2 and 3. Carr holds a master’s in molecular genetics and a bachelor’s in natural resources and environmental sciences from the University of Illinois.