Doane Daily Cotton Commentary

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Soybean

Soybean Replant Decisions

Angela Thompson

Corn and Soybean Ext. Specialist

Jackson, Tenn. (May 15, 2008) – I have had several calls this week about replanting. We knew that our seed quality was not great this spring and cool/wet planting conditions have all contributed to erratic emergence and seedling mortality.

• For fields planted less than 2 weeks ago, I strongly encourage folks to wait until next week, after temperatures warm up, before they make their replant decisions. Seeds that have sprouted but not emerged can still contribute to a stand.

• If a field was planted more than 2 weeks ago, and there are not enough living seedlings either above or below ground, replanting should be considered.

Make sure to accurately estimate the viable plants in a field, taking into account both stand and uniformity of stand. Fortunately, a soybean plant can compensate for a thinner stand by producing more branches and pods per plant and research plots have had some impressive yields with stands of 80,000 or below in good rainfall years.

Maturity Groups

Maturity Group 4 and 5 soybeans with 2 remaining uniform stands of 90,000 to 100,000 plants or more should be kept.

Maturity Group 3 soybeans should be left alone when uniform populations exceed 110,000 (data indicate a MG3 can yield well with even lower populations but only in a good rainfall year or under irrigation).

Skippy Beans

When beans are “skippy” only in spots, consider spot replanting instead of driving over beans to “add to” the population of an existing stand. Populations can be estimated by two different methods.

Regardless of the method used, make counts in areas that are truly representative of the field:

Method 1. Hula Hoop method:

Works great for drilled beans; check 4 to 5 locations per field
 

Table 1. Hula Hoop method for determining drilled soybean populations.

Method 2. Count Number of Plants in 1/1000th of an acre (this also works for corn and other crops):

Works well for planter seeded rows and is pretty accurate; Number counted X 1000 will give per acre population; Make at least 5 counts per field.
7 inch rows = count number of plants in 74’ 8 inches of row (reconsider the hula hoop for easier estimating drilled bean populations).
• 15 inch rows = 34’ 10 inches
• 20 inch rows = 26’ 2 inches
• 30 inch rows = 17’ 5 inches
• 36 inch rows = 14’ 6 inches