Wet weather not only caused planting delays and replants, but also has impacted the soybean crop.
Based off the most recent planting progress report, Illinois’ soybean crop is about 85 percent planted as of June 4, which is close to being on track from last year and the five-year average (Figure 1).
Figure 1. Soybean planting progress in Illinois.
Over the past month many environmental challenges have caused several fields to either be planted late or replanted. Some growers have abandoned their proposed corn crop and switched to soybeans. Walking fields over the past few weeks, several things have caught my attention: Herbicide interactions, stand establishment and early growth.
With cool, wet soil conditions after soybean planting, young plants have once again shown symptoms of protoporphyrinogen oxidase (PPO) herbicide burn (Figure 2). Burn occurs when soybeans are planted along with a PPO herbicide, followed by excessive rainfall. In this situation, the hypocotyl and cotyledons are exposed to the herbicide and can be burned.
PPO herbicide burn is more common during the cool/wet soil conditions we are experiencing this year. I have seen this issue in a lot of fields over the last 10 years during wet springs, and most of the time there is no economic impact. The field needs a little time to metabolize the herbicide and recover.
Figure 2. PPO damage on emerging soybean seedlings.
On a more positive note, I have been impressed with the quality of weed control that we are getting for waterhemp and other weed types, considering the environment that the herbicides have been placed into.
Like corn, soybean emergence and stands were impacted by planting date, soil temperatures, soil moisture and overall soil condition. In some areas, we could see a clear line where planting stopped one night and started again the next morning. This indicates how much heat was given to the seed before the coming rain event. In some cases that extra day was the difference between keeping a stand and replanting.
Emergence through the soil crust was more of a struggle in fields with low organic matter and in fields that may have been tilled a bit excessively, creating fine soil particles. These issues reduced the stand count. In most cases, replant was necessary, either the full field or just low areas where water held on too long. Since most soybeans are treated now, I came across very few issues where a disease alone reduced the stand.
My advice: Always take a stand count to estimate your stand while noting its consistency. Remember, a final stand of 100,000 per acre will maximize yield. However, if there are gaps or missing spots, take the time to fill them in.
I have been watching several early planting fields (last week of April), and have been very pleased with the emergence and early vigor expressed by the plants. These observations support the consideration of planting soybeans earlier in the growing season. On the other hand, some of the later-planted fields are still struggling to emerge in some areas due to soil crusting. While out scouting soybean fields, observe the growth stage of the soybeans and track growth progress.
Over the next few weeks, it will continue to be important to scout soybean fields for pest and weed pressures and nutrient deficiency, as they can prevent a field from maximizing production. Tissue sampling is an agronomic tool that is becoming increasing popular to help understand soybean plant needs and whether the soil can supply the demand. It’s important to be proactive and communicate with your laboratory for sampling supplies and protocols.
CCA Todd Steinacher is an agronomist at AgriGold. He works with growers to better manage their nitrogen and weed control needs, along with understanding the best way to estimate cost to generate a strong ROI. He is a 2017 Illinois Soybean Association CCA Soy Envoy.