So how is the soybean crop faring in Illinois? The USDA has its annual yield predictions coming out in August and September and this week the Pro Farmer Crop Tour will make its predictions for each state. These recent rains will sure help—as we all know “August rains make grain.” It is probably fair to say that soybean yield will be above average even though parts of the state may have suffered some setbacks from too much rain or not enough rain.

I remember hearing Bryce Anderson from DTN speak at ISA’s soybean summit in Rockford last March. He stated that spring would come early and be warm and dry until mid to late April. Then it would turn wet and moisture would be ample through June and into July. Corn would pollinate just fine but soybeans would be hit by a dry August. Much of this was based on the El Niño / La Niña cycle. Well, it turned out that two-thirds of the prediction were true—through July which was drier and hotter than expected. Corn yield may have been hit by signs of tip-back, but recent rains will help the soybean crop.

If you remember back to late March and early April, planters took to the field early due to a warm and dry early spring. Planting got off to a fast start and corn went in early with soybeans. Then conditions changed and it turned cool and wet like Anderson predicted. Temperatures dropped. Fields stayed wet. Growers struggled to plant and even had to replant. Of course, cool and wet conditions can exacerbate seedling diseases and SDS. Growers were finally able to get planted by the end of May for the most part. Wheat matured early and double crop soybeans were planted early. But in July, conditions were hot—a week of hot weather followed by a week of moderate weather along with high humidity. Finally, conditions moderated in August, turned more pleasant and were favorable for producing high yield soybeans.

Now, as we enter the downside of the soybean season with moderate conditions, when will the crop mature? The USDA’s crop progress report posted August 15 has 93 percent of the soybeans blooming and 78 percent setting pods. And the crop condition report had 80 percent of the soybeans being in good to excellent conditions. Recent rains will help the crop along and finish off strongly.

Soybeans are hitting the R5 stages (pod fill) now and developing and filling seeds. This stage is characterized by rapid seed growth or seed filling. At about R5.5 the plant attains its maximum height, node number and canopy development; the plant’s ability to contribute N (via N fixation) begins to drop rapidly; and seeds begin a period of rapid growth. At the same time the plant starts to recycle nitrogen and mobile nutrients from leaves and stems. This continues until about R6.5 at which time about 80 percent of the total seed dry weight is done.

At R5 it takes about 35 days to reach R7 (plants yellowing and shedding leaves with one mature colored pod) and another 10 days till R8 or maturity (leaves shed, plants brown and 95 percent of pods reach mature color). Then it’s just a matter of monitoring beans till they drop to 14 percent—then have at it with harvest.

If your crop is at R5, you are probably looking at October 1 to 8 to begin harvest. Of course a warm and dry September could speed that up or a cool and wet September could slow that down.

Agronomist Dr. Daniel Davidson posts blogs on agronomy-related topics. Feel free to contact him at djdavidson@agwrite.com or ring him at 402-649-5919.