Mississippi Soybeans: 9 Planting Time Decisions

©Debra L Ferguson Stock Photography

Soybean producers are faced with making decisions about planting date and planting time inputs every year.

This blog contains most of the information you will need to prepare for and conduct planting. I have listed what I consider the main issues that should be considered at planting time, and have linked to resources that contain pertinent information about these subjects. Please bookmark these links for use during the next couple of months so that you will have access to any of the sources and their information with one or two clicks.

1. Soybean Maturity Group (MG).

SOYMAP is a new tool that can be used to determine the soybean MG that best fits a particular planting date at a specified Midsouth location. Both the tool and a video that explains its use are available through the above link.

Guides for choosing soybean variety MG for the states of ArkansasMississippi, and Tennessee have been published.

2. Varietal sensitivity to Metribuzin.

With the continual evolving of herbicide-resistant (HR) weeds, preemergent (PRE) residual herbicides are increasingly being used as a component of weed control programs to control and/or delay the development of HR weeds and to introduce multiple modes-of-action. Many of these herbicides are mixes that contain metribuzin.

Varietal sensitivity to metribuzin exists, especially when varieties are planted on coarser-textured soils with low organic matter following PRE application of metribuzin. Thus, producers need to ensure that their selected varieties are tolerant of metribuzin in situations where metribuzin-containing residual herbicides will be used. See results from the Varietal Screening for Metribuzin Sensitivity.

AgFax Weed Solutions


3. Nematode-resistant varieties.

Click here for information about the nematode pests that may affect soybeans grown in the Midsouth. Information about resistance in current varieties is available from Midsouth states’ variety trial results, extension service personnel, crop consultants, seed dealers, and originating seed companies.

4. Planting date.

Early planting is now the norm in the Midsouth as indicated by results from the most recent NASS survey, which showed that producers in Arkansas, Louisiana, and Mississippi had planted an average of 38%, 55%, and 51% of their soybean crop by May 7 over the last 5 years. In some years when weather permits, a significant acreage of soybeans is planted in mid-April in these states. Click here for early-planting tips.

The decision of just how early to plant soybeans should be based on the safest early planting date at a particular location to avoid cold injury to emerging seedlings. Click here for a table that gives the estimated dates of the last spring frost (36°) and freeze (32°) based on 90%, 50%, and 10% levels of probability at indicated Mississippi locations.

Click here to access the NOAA-NCDC site that provides the same data for other Midsouth states. These data should be used as a guide for choosing a safe early planting date for the latitude of the intended planting site.

Remember, early-planted soybeans will usually take up to 4 days longer to emerge compared to soybeans planted a month later, so this extra time should be factored into a projected planting date to avoid a spring cold event that may damage emerging seedlings. As a producer, you must decide the level of risk you are willing to take when considering the earliest safe planting date in relation to air temperature.

Additional information that should be considered when selecting a planting date is provided in a white paper on this website.

5. Seeding rate.

There is no perfect seeding rate for all planting conditions. However, estimates for optimal soybean plant populations provide a reasonable starting point for most conditions in the Midsouth.

The University of Illinois developed a seeding rate calculator (see also Calculate your soybean seeding-rate needs that is available for the PCAndroid, and iPhone/iPad platforms). Using these tools takes the guesswork out of this important calculation.

7. Seed treatments.

The most important point to remember about seed treatments is that a product that is effective against both seed- and soil-borne fungal pathogens is the only seed treatment product that should be used in all situations since these pests are the ones most likely to reduce emergence and lessen the likelihood of attaining an acceptable stand.

Click here for information about fungicide seed treatments that should be used to protect against the prominent pathogens that will affect emergence of soybeans.

Seed companies often apply a predetermined product to their seed. These products will likely contain all seed treatment pesticides (fungicides, insecticides, nematicides) that are currently available for sale by those companies.

Also, these “cadillac” treatments will usually be priced much lower than their individual components if they were applied separately; however, they will still cost $12-$15/acre. A quality broad spectrum seed treatment fungicide will only cost about $3/acre, so there is still a significant difference in these prices.

Consider the following points when deciding whether or not to use seed treatment pesticides in addition to fungicides.

  • Most only provide limited protection for the first 30 or so days from planting–thus their use for other than achieving a stand may not be cost-effective.
  • They will only result in slight to no yield increases, and thus may not be cost effective, especially on sites that are not known to have a significant presence of the targeted pest.
  • They offer little to no help in achieving an intended stand.
  • They offer no enhancement on sites that have not been determined to have the targeted pest(s).
  • Pathogen-specific products such as ILeVo (specific against SDS pathogen) should only be used where there is evidence that this disease has caused prior yield loss.

This, then, leads to the conclusion that broad spectrum seed treatment fungicides are the only seed treatment products that should be used in essentially all cases because their use will virtually guarantee achievement of the desired stand on most sites that will likely have soil-borne fungal pathogens such as Pythium.

This is especially important for early soybean plantings where failure to achieve a stand will cause a loss of the early planting yield advantage.

7. Handling bulk planting seed.

Today’s high cost of planting seed makes this step in the planting process a money-saving issue. Click here for valuable tips on how to avoid damage to seed during the handling process.

8. Disposal of treated seed.

As environmental stewardship becomes more important and necessary, the guidelines outlined here and in the linked articles should be followed.

9. Iron deficiency chlorosis (IDC).

Iron Deficiency Chlorosis occurs to some extent in soybeans that are grown on the high-pH soils in the Black Belt region of east Mississippi. This deficiency can cause moderate to severe yield reductions. The best strategy for managing IDC is to select a soybean variety with tolerance.

Ratings of tolerance to IDC made by the originating company (if available) are likely the best source for selecting tolerant varieties. Ratings against IDC of several varieties grown in East Mississippi can be found in the above-linked IDC article.


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