The farmers tending the Crop Watch ’16 field didn’t set out to plant 45,000 plants per acre. They used variable-rate planting, topping out in the mid-30,000s on what they believed were their most productive soils.
This year when corn emerged in the field, after weeks of very cold, wet weather after planting April 27, stands ranged from the high 30,000 plants per acre to 10,000 plants per acre or less. But since most of the field had stands of 25,000 plants or more, they left the corn. In late May, they spotted in seed where they thought stands were weak.
As a result, there are areas in the field where the stand is thicker than the original goal. It's only a few areas. However, Dave Nanda, crops consultant for Seed Consultants Inc., sponsor of Crop Watch ’16, found one of those spots. His stand count in early June was 45,000 plants per acre.
High population can be a stress in its own right. Then in late May and early June, the rains quit coming for a while. It didn’t take long for the areas where stands were thick to begin to show signs of moisture stress.
Corn rolled in a few spots with very high populations. Rolling is a defensive mechanism, and doesn’t mean plants are suffering to the extent that yield will be affected, Nanda says. Plants roll their leaves if moisture supply is on the edge to conserve moisture.
Soon after the top picture was taken, rains began to fall again on this field. It rained regularly, and in copious but not excessive amounts, through mid-July. The corn made a noticeable turnaround in spots where the stand was thick. Note improved plant health of the same corn, as shown in the bottom photo.
What will late-season bring?
Whether the corn stays healthy will depend on late-season weather conditions, Nanda says. There was ample moisture for good pollination, so the yield potential is there. The question is, what will happen during grain fill?
Corn plants still make an important decision during grain fill that impacts yield significantly, Nanda notes. They determine how plump kernels will become. If weather conditions remain good, the signal will be to keep filling kernels. If it turns dry and plants stress, the signal will be to cut back on filling kernels and finish as many viable kernels as possible.
“Yield where populations are high will depend on what happens during grain fill,” Nanda concludes.