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Soybean planting brings questions

With planting time fast approaching, some last minute questions have surfaced ranging from seed treatments to when to stop planting Group 4s.

From a seed treatment standpoint there are two concerns:

  1. Should I use a seed treatment?
  2. What should I use?

First, keep in mind we have experienced a major shift in our planting window. A seed treatment is needed when planting early with the potential for cool, wet conditions, or later under wet, hot conditions.

When planting under optimum conditions we rarely see a benefit unless seed quality is poor.

Ninety-nine percent of the time, if you lose a stand of soybeans it is due to pythium not rhizoctonia.

Use the proper seed treatment to control (primarily) pythium. This will be either Apron or Allegiance. You can broaden the spectrum by adding materials such as Vitavax, Maxim or Quadris.

Captan and Thiram are seed protectants only. Once the seed coat cracks they are finished (very short-lived).

If I was going to gamble and save money, I would use a straight pythium product. With the cost of seed today, however, it is too inexpensive not to protect yourself with a good broad-spectrum mix.

Seed treatments make a difference. If they save you a replant in just one year that savings will pay for about 12 to 15 years of seed treatment costs.

As you look at your planting seed, if they are not pretty and shiny, they may already have some fungi on the seed coat. This is when materials such as Vitavax, Maxim and Quadris will help.

In the mid-1980s we had a bad fall, and germination percentages were lower than normal. We found that adding Vitavax increased germination by 15 to 30 percent. That led to the widespread use of Vitavax.

The fall of 2004 was no different. Due to a shortage of the best varieties and fall harvest weather, this is not the year to skimp on seed treatments. I encourage you to never take this chance, particularly if you are planting early on flat, heavy, poorly drained soils.

We have figured out why we replant, so why take the chance?

Seeding rates are another concern. With the recent increase in seed costs, I expect many will do a better job of setting planters.

Final populations of 130,000 to 150,000 plants per acre are adequate on early planting. As conditions improve, the number can be reduced (100,000 to 120,000). Many would be surprised at how low a population you can have and still attain excellent yields.

This hinges on several criteria, such as time of year, health of emerged plants, and plant uniformity.

Some research has shown the benefits of higher populations for ultra-early maturity groups and for suppressing weed populations. Given seed costs, however, I do not believe many will want to plant 200,000-plus seed per acre.

Some Mississippi soybean acreage was planted the first few days of March. This is extremely early, but we have seen success with these ultra-early plantings over the last three years.

One point many fail to realize is that as long as it stays cool, these seed are not going to emerge.

A good rule of thumb is to plant your corn first and then start on soybeans. Fifty degrees is the minimum germination temperature for corn, 55 degrees for soybeans.

Drainage is a big concern in the equation. Frosts are not as much of a concern as some believe, however, an extended freeze will cause problems on emerged plants.

Last year was an anomaly (as far as early planting was concerned), but yields support the practice, particularly dryland plantings.

Many have asked when to stop planting Group 4s. The answer is never.

If you have done your homework and selected a good high-yield variety, you will be better off planting that variety than swapping it for a Group 5. As you plant Group 4s later, you shift their maturity. They become a Group 5, maybe an early Group 5, but delayed planting shifts the maturity. Odds are you are going to swap for a Group 5, but I can guarantee you that the best yield potential Group 5s are gone, so why settle for picked over Group 5s when you already have a top-yielding Group 4? As you plant later, yields may decline, but that all depends on when it rains.

Alan Blaine is the Mississippi Extension soybean specialist. e-mail:

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