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Pro Farmer Midwest Crop Tour: Soybeans Get Double Stress

00:00AM Sep 05, 2008
Beans don't like wet feet in the spring and early summer, and they really don't like a dry August. This year, the Midwest bean crop got the dreaded "double dose.” And the stresses associated with it were evident on each day of the Pro Farmer Midwest Crop Tour.

We consider the Crop Tour a discovery process designed to give crop scouts an inside look at soybean yield potential. That's why we count pods. Unfortunately, we're still struggling to find that "silver-bullet” correlation between pod counts and final yield for each tour state and for the national average bean yield. But there are bits and pieces of evidence we collect along the way that tell the story of each year's bean crop.

Getting samples
We count plants in a 3' section of row in each bean field we sample, and we pull three plants from each field to count pods in order to determine a pod-per-plant average. Those are the key numbers we use to calculate the number of pods in a 3'x3' square. How-ever, there's another reason we count those plants and pods.

When counting plants, crop scouts get down inside the canopy of the bean field. That's where the real story of the bean crop is written. That close examination at ground level gives scouts a chance to catch disease pressure; pulling plants gives them a good chance to assess soil moisture by the dirt that clings to roots; counting pods gets their eyes in the right spot to find leaf diseases, insect feeding and those aphids that cling to the underside of leaves. And putting fingers on those pods automatically gets scouts to assess pod fill.

It's an amazing process! Inexperienced, nonfarming crop scouts catch on to this simple process very quickly. And when they spot something in one field they didn't see in the last one, it generates all kinds of questions to the farming scouts that travel every route. Those questions alert the in-the-know scouts on the route that something is up in the field and they need to take a closer look.

As I said, it's a discovery process on Crop Tour. As scout directors of the tour, we do our best to point others in the right direction to let that discovery process work.

Stress factors
Two issues are impacting the Midwest bean crop from Columbus, Ohio, to Columbus, Nebraska: The wet spring caused late planting and it's now too dry.

Some crop watchers like to think a late-planted bean crop can catch up to a nor-mal development pace later in the season. Well, the bean plant does catch up…but conditions have to be nearly perfect to allow the bean seed inside the pod to catch up to normal.

Beans from a late-planted crop typically are smaller than those from a timely planted crop—it's really that simple. Because a bushel of beans is determined by weight and not by some specific number of beans, the bigger the bean, the higher the yield; the smaller the bean, the smaller the yield. Seems obvious enough, but that fact appears to be forgotten in a late-developing year as the plant's appearance gives the impression of development while seed size lags behind.

August weather is always important in determining a bean plant's ability to make a "big bean.” We've said for years that if scouts have mud on their boots during Crop Tour, it's easy to underestimate yields. Well, the opposite is also true: If scouts don't get any mud on their boots, it's easy to overestimate yields.

Unfortunately, this year's bean crop is late in developing and there wasn't much mud on scouts' boots this year.

Top Producer, September 2008