Parts of the upper Midwest experienced below-freezing temperatures during the last few days of May. In this week’s #AskTheAgronomist, Latham Precision Agronomist Phil Long covers how to evaluate frost damage in corn and soybeans.
Soybean stands can suffer from a wide variety of problems that will reduce population. Hail, diseases, insects, cold soil temperatures at planting, compaction, and planter failures can all affect the stand individually and in combination.
Stand reductions almost never occur evenly across the field. Here are some basic steps to help evaluate soybean stands and decide if re-planting is necessary.
Take 10 stand counts in the area with the worst damage and 10 counts in the part of the field that was not affected or affected just slightly. At each point, measure off 10 feet of row and count the number of live, viable plants. Then calculate the average of your 10 points and compare them to the table below to see how many plants per acre you have remaining.
A stand of 100,000 evenly distributed plants generally gives you optimum yield. As the growing season progresses, however, it is much more difficult to establish a good stand. A stand of 75,000 on May 15 is inadequate, but you might be better off leaving a stand of 75,000 plants if it is July 1.
Planting soybeans on or before June 1 averages 95% of expected yield. In a five-year Latham Seeds’ study, there was no significant yield difference in soybeans planted before May 15. Planting dates included late April, early May and mid-May. We did not see yields drop to 85% or lower until after June 15.
Our results are similar to studies done by university researchers. If you farm below the line from Watertown, SD through the Twin Cities and over toward Green Bay, Wisc., I recommend staying with soybeans in your normal maturity until mid-June. After June 15, consider the precipitation expected in late June and early July because the biggest threat to establishing a late soybean crop is lack of rainfall. If you are north of that line, you may need to switch to an earlier variety a week or so sooner.
“In farming, you only get one chance every year, so it’s worth it to do it right the first time.”
That statement is so very true. Below are a few things to keep in mind to optimize your corn and soybeans yields:
Soil Moisture. Working ground when it is too wet leads to slabbing and clodding of the soil, so areas within fields dry at different rates. A kernel of corn imbibes, or takes in, about 30% of its weight in water during germination. When kernels in a row are exposed to varying amounts of soil moisture, their germination rates and emergence will vary from plant to plant. The result is uneven emergence, poor early growth and potentially severe stand loss. Soybeans need more water at germination, taking in about 50% of seed weight on average. As with corn, good seed-to-soil contact is critical, so avoid cloddy conditions.
Soil Temperature. Corn germinates best when soil temperature is close to 50° F. Approximately 120 growing degree units (GDU’s) are required for corn to emerge. During periods of cool temperatures, it can take several days to achieve those GDU’s. Once a corn seed germinates, it can exist for about 14 days on the energy that is contained in the endosperm. Under ideal conditions, the seed will emerge and develop a root system in much less than 14 days. Most researchers agree that soybeans emerge best when the soil temp is 55° F or warmer. Avoid planting soybeans if the temperature is below 55° and a cold rain/weather event is expected within 24 hours after planting.
Planting depth: Soybeans respond best when planted at 1¼ to 1½ inches deep and should never be planted deeper than 2 inches! Remember, a soybean seedling must push that cotyledon through the soil as it emerges. The soybean seedling requires much more energy than a corn seedling with its narrow coleoptile (shoot). Target depth when planting corn is 2.5 inches. Planting corn shallow is as bad as planting soybeans too deep because nodal roots will not develop properly and “Rootless Corn Syndrome” may result.
Soybean inoculant: Old-timers say if soybeans have been planted in a field within the past four to five years, then an inoculant is not necessary. However, recent studies and more advanced inoculant formulations show otherwise. Using inoculants in light, sandy soils, as well as weather-stressed (flood, drought, etc.) fields have shown increased plant health and improvements in overall yield. Consider running side-by-side trials on your farm to see if inoculants will work for you.
Problems like sidewall compaction, surface crusting, herbicide injury, seedling insects and seedling diseases can all lead to delayed plant and root development. These, and many others, can all cause uneven emergence and poor stands in corn and soybean. That’s why it’s important to control what you can to set up your crops for success!
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XtendFlex soybeans, which were approved for global sale in September 2020, will be an important tool to manage resistant weeds. The combination of tolerance to dicamba (XtendiMax®, Engenia® and Tavium®), glyphosate (Roundup®) and glufosinate (Liberty®) herbicides offers a unique triple option of choices to control a wide range of grasses and broadleaf weeds in soybean fields.
Farmers who have used Roundup Ready 2 Xtend® soybeans are generally happy with their yields but desire better weed control options. Most farmers with whom I’ve visited believe they must wait as long as possible to apply the post-emergence dicamba products with the Xtend system. This application was later than ideal, resulting in weed escapes and even off-target movement of the dicamba herbicide to neighboring soybean fields that weren’t tolerant to that herbicide.
Using the XtendFlex system will allow farmers to apply dicamba herbicide earlier. They can spray either pre-emergence or early post-emergence when weeds are at labeled heights and are most sensitive to the herbicide. This should also greatly reduce the likelihood of off-target movement of dicamba to nearby sensitive crops.
Another benefit of the XtendFlex system is that farmers can apply Liberty herbicides up to the R2 stage of growth if there are any weed escapes. It is still highly recommended that weed management programs start with a pre-plant or early pre-emergence residual herbicide like Warrant®, Authority® or Sonic®. Regardless of which herbicide you use, please read and follow all label recommendations.
At press time, Latham Hi‑Tech Seeds will have seven XtendFlex soybeans available for spring 2021 planting:
All of these XtendFlex releases carry strong Soybean Cyst Nematode tolerance. Contact your Latham Dealer or RSM for current availabilities.
Variable rate (VR) seeding in corn has been a frequent topic of conversation for years, but now that conversation is shifting to VR seeding soybeans. Before planting VR seeding soybeans, we must change the way we think.
When your yield potential goes up in a corn field, we increase population. When corn yield potential goes down, we decrease population. Makes sense, right? It’s the opposite for soybeans. When yield potential increases, lower your planting rate in a soybean field. When your yield potential decreases, increase the planting rate. Our trials to date have shown the most return on investment in lower-yielding environments where population was decreased.
Why invest more in a geography where yield potential is less for soybeans? There’s good reason! Percent germination in soybeans is one big reason.
When you plant tougher areas in the field, you’re not going to achieve 100% of your germination rate. Now think of your high yielding areas in your field… There is a much greater chance you will achieve close to 100% germination there. High-yielding areas typically have better soils and drainage, so it makes sense to plant more seed in low-yielding areas to increase the germination rate.
We enjoy sitting down with farmers and talking about whether VR planting is right for them. Our Data Forward™ team is here to help you get comfortable with implementation. Phil Long and I love to do On-Farm Trials in your own fields, so this could be a good starting place for farmers wanting to experiment with lower seeding rates. We can experiment on a smaller scale while placing learning blocks throughout the field. Using learning blocks and on-farm research allows us to compare different zones of a farmer’s field and to also compare to previous years.
Imagine the savings if we can drop soybean planting populations by even 20,000! The savings from reducing planting rates from 160,000 to 140,000 can then be invested into seed treatment or something else that protects yield and helps you achieve optimal germination. This allows farmers to continue to achieve higher yields while lowering planting populations.
Give your Precision Agronomy Advisors a call today! Let’s start a conversation about conducting on-farm research.
Phil Long tackles both the corn and soybean seed size discussion in the videos below. Tune in to learn if seed size matters on your farm!
XtendFlex soybeans, which were approved for global sale in September 2020, will be an important tool to manage resistant weeds. The combination of tolerance to dicamba (XtendiMax®, Engenia® and Tavium®), glyphosate (Roundup®) and glufosinate (Liberty®) herbicides offers a unique triple option of choices to control a wide range of grasses and broadleaf weeds in soybean fields.
Farmers who have used Roundup Ready 2 Xtend® soybeans are generally happy with their yields but desire better weed control options. Most farmers with whom I’ve visited believe they must wait as long as possible to apply the post-emergence dicamba products with the Xtend system. This application was later than ideal, resulting in weed escapes and even off-target movement of the dicamba herbicide to neighboring soybean fields that weren’t tolerant to that herbicide.
Using the XtendFlex system will allow farmers to apply dicamba herbicide earlier. They can spray either pre-emergence or early post-emergence when weeds are at labeled heights and are most sensitive to the herbicide. This should also greatly reduce the likelihood of off-target movement of dicamba to nearby sensitive crops.
Another benefit of the XtendFlex system is that farmers can apply Liberty herbicides up to the R2 stage of growth if there are any weed escapes. It is still highly recommended that weed management programs start with a pre-plant or early pre-emergence residual herbicide like Warrant®, Authority® or Sonic®. Regardless of which herbicide you use, please read and follow all label recommendations.
At press time, Latham Hi‑Tech Seeds will have seven XtendFlex soybeans available for spring 2021 planting:
All of these XtendFlex releases carry strong Soybean Cyst Nematode tolerance. Contact your Latham Dealer or RSM for current availabilities.
Does varying seed size can have effect germination and emergence? Tune in to find out! #AskTheAgronomist
:39 – Topic Introduction
2:05 – Local seed production
2:45 – Germination and emergence
6:15 – Planting date
10:30 – Establishing high yield