by Wayne Flanary, Regional Agronomist, CPAg, CCA
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Early planted corn is in the dent stage. This is known as the R5 stage. This occurs approximately 35 to 40 days after silking. Corn in this stage is starting to form hard starch at the top of the kernel. This can be seen as a line across the top of the kernel.
The impact of the hot weather may have reduced yields by the ear tip kernels aborting. These kernels start to form but the plant realizes because of the hot dry weather, it cannot continue to fill all of the fertilized kernels, so it will put its resources to filling those which it feels it can handle given the stress conditions.
Once corn has reached the dent stage, stress only affects the weight of individual kernels. The kernels are far enough along that abortion of kernels will not occur.
Later planting of corn can be in the dough stage which kernel abortion can occur. Examine corn ears for grain fill. If the tip kernels are white and never started turning to yellow kernels, the kernels were not pollinated.
As for soybeans, we are in a critical time for yield. During first half of August, we are creating pods and filling seed within pods. Most blooming that occurs now with Group III soybeans will create few pods.
The soybean plant reaches the maximum height and weight. It will now redistribute its weight and nutrients to fill seeds within pods. This is known as R5 stage and this is when there is one-eighth of an inch size bean in one of the four uppermost nodes of the plant.
This is critical stage for soybean yield. Soybeans need water and nutrients for pod and seed fill.
Rain has been timely for many counties whereas others have been impacted by the high temperatures combined with the wind. Soybeans and corn wilted during this time causing plants to adjust to handle the stress.
At this point, corn yields will be good in many areas where timely rains provided soil moisture and for soybeans, the weather will be critical for yields.
For more information, contact Wayne Flanary at 660-446-3724 or Heather Benedict at 660-425-6434, Regional Agronomists, University of Missouri Extension.