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Replanting reduced: Seed treatments give soybeans edge

The risk associated with early soybean planting is not nearly as great as many of you may believe. I admit we need more work in the area of soybeans' ability to withstand cool temperatures, seedling survival after exposure to cold temperatures, cold tolerance among varieties, seed coatings, etc. However, history has proven the risk is much greater with later plantings.

Emergence this spring was not as fast as some would have liked. This was due to a combination of cool temperatures and lack of moisture in many areas. Ironically, the planting dates (mid-March) that have been questioned the most experienced the fastest emergence.

Where planting was delayed due to concerns about future weather or dry soil conditions, planting did not resume until mid- to late April. Mid-April is by no means late, but it is probably surprising to many that the earliest dates had the least trouble emerging.

Some feel that delayed emergence makes young seedlings more susceptible to seedling disease. This could happen, but where a good broad spectrum seed treatment is used in conjunction with high-quality seed, we have not observed this to be true.

However, we have observed pre-emergence herbicides delay emergence. This occurs during a big rain at cracking causing slow growth of seedlings, which may set the plant up for pythium.

Avoid this by applying pre-emergence materials early enough to get a rain prior to emergence, essentially eliminating any injury problems.

Since we started using a broad spectrum seed treatment centered around a pythium material, replanting has been reduced significantly. Seed treatments are nothing more than insurance, but they make a big difference when needed.

Are seed treatments needed in all cases? No, but they are too inexpensive to play a guessing game as to when you should or should not use them.

Many of our early plantings were so early that we could have planted without a seed treatment.

I am not willing to take this chance, but I want you to understand that some stands have been achieved prior to any potential activity from seedling disease because it was too cool and free moisture was not available during emergence. I point this out to make you aware that nothing is absolute and exceptions exist in almost every scenario.

I am not suggesting you eliminate a pythium-based program — I just want you to understand why we utilize seed treatments. If you are having consistent stand problems, use of the proper seed treatment can help.

Many believe “once stressed, always stressed.” This all depends on what caused the stress. Just because a seedling takes two to three weeks to emerge does not mean it was stressed.

Slow emergence in April cannot be compared to delayed emergence in June. High temperatures are what cause problems on later plantings; this is not a problem on early plantings.

Planting seed that are of marginal quality is a problem you will live with all season long.

For this reason, it is important to know the quality of your planting seed. Plant high-quality seed first and plant marginal-quality seed under more optimal conditions.

Another question that has surfaced is “if seedlings are slow to emerge, they are predisposed to other diseases.”

As a whole, most of the late-season foliar diseases that we used to caution you about are no longer a problem in the early planting arena. I have read that SDS has been a factor in the Midwest, but that is there, not here.

I will bet you that if they have more SDS on early plantings it is due to excellent yield potential on early plantings versus later plantings.

SDS is a Midwest problem primarily. Sure we see it here, but only when we have an excellent yield potential due to good growing conditions.

Unless it is an extremely susceptible variety, SDS is an excellent indicator of good yields. If it is observed at a higher incidence in the Midwest, I bet the pattern is probably the same. Based on our observations, slow emergence on early plantings will not contribute to a higher degree of SDS. If it happens, it is due to higher yield potential.

Many have expressed concern about possible cold weather damage, but as of late April we had not experienced any temperatures that caused any alarm.

Planting early is risky, as is planting late, but in a dryland setting you can better maintain your yields early versus late.

You should be aware that all planting systems carry a certain degree of risk: seedling disease, cutworms, hail, flooding, drought, saturated soil conditions just to mention a few. We may at some point push planting dates too far, but it will be no riskier than anything else we do. We may have a field that might experience freeze damage (not frost), but it will not affect the entire crop, due to variability in planting dates.

Those of you who have been utilizing this system for several years probably have a better grasp of this scenario. If you do have problems in the future it will be nothing more than a replant situation (in some fields, not all), and this is a practice we are used to doing more often on later plantings than early.

As you continue to fine-tune this system on your farm, keep one point in mind. If you have to err, err early not late.

Alan Blaine is the Mississippi Extension soybean specialist. e-mail: [email protected].

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