If you're still uneasy about your soybean stands, get out your kid's hula-hoop and head to the field. Roll it in at least five locations. Know the inside diameter of the hoop, and count the number of plants inside the hoop at each location. Average them together.
At this late date, you can go pretty low and still decide to save the stand instead of tearing it up and replanting. There are cases of reaching more than 50 bushels per acre with varieties of two decades ago planting this late, but they are few and far between.
Shaun Casteel, Purdue University Extension soybean specialist, says that soybeans have a tremendous ability to compensate. As long as stands are relatively evenly spaced and you can control weeds, soybeans can branch out and sources more than you might think.
Here's information based on the Purdue University Corn & Soybean pocket Field Guide. You can get is in paperback or as an app for iPads.
The soybeans in the hoop pictured come out to about 140,000 plants per acre. The Guide indicates 100% yield potential, even if you were hoping for more plants. In fact, you have to drop below 120,000 before you lose any yield potential at all. In 30-inch rows, you can still achieve 100% of yield at 80,000 plants per acre.
This may surprise you. If you're looking at only 40,000 plants today, you can still expect 87% of your yield based on a number of trials that went in to making the table. If you were hoping for 50 bushels per acre, that's still better than 43 bushels per acre.
Related: Soybeans Will Overcome Thin Stands
The alternative would be to replant. The Guide says that if you replant June 30, you can only expect 70% of normal yield, even with a full stand. That 50 bushel goal now becomes 35 bushels per acre, and may vary up or down slightly depending upon where you're in the state.
Leave 40,000 now or replant? The numbers are clear – leave it.