As producers gear up for planting soybeans, many related management decisions have already been made; e.g., seed of selected varieties have been secured, the appropriate seed treatment has been or soon will be applied, and row spacing and seeding rate are set.

However, near or at planting time, there are other management decisions that warrant extra attention based on the desired planting date, selected weed management program, and soil properties of the production site.


Earliest Safe Soybean Planting Dates

Early planting is now the norm in the Midsouth. 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.

An article on this website contains 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. These data should be used as a guide for choosing a safe early planting date at indicated Mississippi locations.

Remember, soybeans will usually take 7 to 10 days or longer to emerge when planted early, 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.

Guidelines for Using Preemergent Herbicides

Management of glyphosate-resistant (GR) weeds in soybeans has become paramount. Preemergent (PRE) residual herbicides are increasingly being used as a component of weed control programs to control and/or delay the development of GR weeds. Details for using residual herbicides to control herbicide-resistant (HR) weeds is explained in a general concepts article on this website. Guidelines for using residual herbicides to control GR marestail and GR Palmer amaranth are presented in additional articles.


Metribuzin-Tolerant Soybean Varieties


Metribuzin is a very efficacious residual herbicide, with activity on broadleaf and some annual grass weeds. It offers a unique herbicide mode-of-action for soybean weed control. Several of the residual herbicides listed in the above articles 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, or on clay soils when the highest rate is used for enhanced control of certain weeds.

Thus, producers need to ensure that their selected varieties are tolerant of metribuzin in situations where metribuzin-containing residual herbicides are used. A link to a list of these varieties is in a blog on this website.

Strategies for Managing Iron Deficiency Chlorosis

Iron Deficiency Chlorosis (IDC) 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 of private varieties to IDC made by the originating company are likely the best source for selecting tolerant varieties. Thus, producers need to ensure that varieties that are selected to be grown on suspected IDC sites are tolerant of the conditions that result in IDC.

Composed by Larry G. Heatherly, Mar. 2013, larryheatherly@bellsouth.net