Plug holes in your soybean regime

Wait to increase soybean yields? Then imagine putting the crop’s maximum yield potential — around 100 bushels per acre today — in a bucket, a bucket with six or seven holes in it, advises Karen Corrigan, of McGillicuddy Corrigan Agronomics.

To figure out how to harvest more of that yield potential, figure out which hole is leaking the most beans in your operation and address that issue first.

Holes that she often sees include:

1. Using poor seed

Good cheap seed does not exist. It is a myth perpetuated on the Internet. It doesn’t pay to skimp up front and limit your yield potential from the beginning. Buy seed from a reliable source that tests its seed for germination and vigor.

2. Choosing the wrong variety

Each variety has characteristics that will help or hurt it in extreme environments or high populations. If you have a tough field or are planning on pushing your populations, be sure to tell your seed representative so he or she can make sure you put the right varieties on the fields that will give them the best potential for success.

If iron chlorosis is an issue, be sure to select a variety that is more tolerant.

3. Planting in compacted soils

“Soybeans have tap roots, but those roots are not indestructible. They need to be able to grow straight down without any obstacles,” Corrigan says.

A soil density layer will force the root to exert energy looking for an adequate area to continue moving downward. Also, the vascular activity of the plant can be disrupted when roots kink.

4. Underfertilizing

Although soybeans are generally not fertilized, they do use a fair amount of potassium and phosphorus. Forty-five bushels of soybeans use as much potassium as 200 bushels of corn.

5. Failing to inoculate

Soybean plants produce their own nitrogen, but only if they have lots of large, healthy rhizobia bacteria on their roots. Inoculating seed correctly increases the likelihood that the rhizobia population is high enough.

It’s especially important to inoculate if the field has been in a non-legume for three or more years; is coming out of the Conservation Reserve Program; or has any soil conditions that would inhibit rhizobial growth, such as high pH.

“Inoculants are alive — so don’t kill them before you put them into the soil. Use new stock. Don’t freeze or thaw the jug. Don’t heat it or subject it to direct sunlight. Make sure that your seed treatments are compatible with the inoculant,” she advises.

6. Not controlling weeds early

Controlling weeds in the first two to four weeks after planting is crucial to high yields. Volunteer corn is also a big problem.

In Iowa State University trials, one volunteer corn plant per 10 feet of row reduced yield 1.3% compared to a treated check. Generally, there are many more than one plant per 10 feet of row, particularly when there are clumps of volunteer corn. In University of Minnesota trials, soybean yields fell 1% for every 75 clumps of volunteer corn per acre.

7. Planting too late

Plant the soybeans as early as you can without freezing them off. Research indicates that the longer soybeans flower the more pods they are likely to set. Soybeans are indeterminant and make fewer critical decisions early in their life cycles. Pod and seed set decisions come later.

Soybeans can withstand cool, gray weather early on that would adversely affect corn. Soybeans germinate and emerge best when planted between 1 and 1½ inches deep. If it is early, plant closer to 1 inch deep. If it is later, plant closer to 1½ inches deep. It is best to plant into moisture, but do not wait so that emergence is delayed. Soybeans that emerge within seven days will have a better start, be healthier and have a higher yield potential than those that take three weeks to emerge.

It is better to plant soybeans in soils that are 65 degrees F than it is in soils that are 50 degrees F.

8. Not stopping soybean aphids

Begin scouting in late June to early July, no later than the R1 growth stage for soybean aphids. Growth stage R1 to R4 (beginning flower to full pod) is when control of soybean aphids is most important.

9. Letting soybean cyst nematodes spread

If you have any areas that look as if they are infected with SCN, send in soil samples to test for SCN. Take all steps to keep fields from being infested and to keep from spreading SCN to new fields. SCN does not move on its own. It moves with soil, on equipment and by tillage. Be cautious if you buy equipment from an infested area.


This article published in the February, 2010 edition of DAKOTA FARMER.

All rights reserved. Copyright Farm Progress Cos. 2010.