Take the same hybrid- any hybrid. Pick your favorite one if you like. Then go to the field and plant it over a wide range of planting rates. Say you vary planting rate form as low as 16,000 to as high as 40,000 seeds per acre. Even accounting for some seed that doesn't emerge, you will still have a wide range of conditions in terms of plant stand within the field. Some parts of the field will be more than twice as thick as other parts of the field.
Next go into that field just before harvest, say next September, and pull ears from various locations. Pull some from where there are 16,000 plants per acre, then maybe pull some where the populations is 26,000 or 30,000 plants per acre. Be sure to pull ears form the same hybrid at the highest population that you find in the field.
"You may be surprised by what you see," says Dave Nanda, president of Bird Hybrids, Tiffin, Ohio. "If you bring these ears out of the field, lay them on the bed of your pickup and ask your neighbor which hybrid he likes best, based on the ears, he may never suspect that each and every one is the same hybrid- with identical genetics."
That's because environment plays such a huge role in corn development and performance in any one location in any one year, Nanda says. Not only will the ears at 16,000 to 24,000 likely be longer, since there was less competition from neighboring plants, but they may also have more rows of kernels per ear. He notes that's because when the plants were making the decision as to how big of an ear to make, including how many rings of kernels to put on the ear, the plant senses fewer neighbors and decided it could support a bigger ear.
Conversely, when plants are crowded, ears will likely be shorter, even in hybrids that aren't known to flex as much. There may also be fewer rows of kernels per ears. These varying traits and shapes and lengths of ears will likely give the appearance that the ears didn't come from the same hybrids\.
Which population yields the most is a different proposition, Nanda acknowledges. Most trials during the past year indicated somewhere around 28,000 to 30,000 actual plants per acre produced the best yields last season.