The corn has moved into the R3 (milk) stage in most fields. A few later planted full-season hybrids are late R2, and some early planted, early CRM hybrids are late R3 (full roasting ear), but most are just entering R3. There is a chart below showing days in each stage, but this is always relative to temperature and sunshine, not calendar days. These cool morning temps and sunny days (if we can get rid of the smoke) are great considering the dryness we are experiencing, but it also helps slows this crop down, allowing more kernel retention at the end of the ear. This is the first step at this point. Those very last kernels that were pollinated at the end are easily aborted with any stress and we see “tipback” or “nosing” (the article below explains more). Some hybrids will always show this tipback regardless if conditions are perfect or not. Some hybrids may fill to the tip and some may not, either way, just because you see this (or don’t see this), does not mean the crop is in trouble. Many hybrids will still add kernel depth later, that is why a little moisture and some bright sunny and cool days would be ideal to help us finish this crop. All of our fields could benefit from slowing down. Going quickly to tassel and then a nice slow grain fill with moisture and sunshine helped us get those big kernels in 2020 to boost yields.
Yield estimations – As we start going into the fields this time of the year, it is much easier to make kernel counts. 16 around and 34 long is a very common number. (Early on it is fun to count to 44 long, but the smoke has taken some of those tips away). Assuming a harvestable ear count in 17′ 5″ of about 32 ears, gives us 16 X 34 X 32 = 17,408 Now the big variable – how many kernels in a bushel. This is what we have been trying to get a handle on for many years now and what we have learned is that the environment and the hybrid play a big role. For many, using 90 gives you a good estimate. 17,408 / 90 = 193.4 bu/ac
We have been doing our dry down study for many years to watch how hybrids not only dry down, but also to collect data regarding kernel factors. Below is a table with the last couple years summaries by hybrid so you can see the estimate for each one individually.
Look at P0306 and P0157 genetics. Look at how much variation we have seen in 4 different growing seasons. Using 85 or 61 is the difference between 205 bu/ac and 285 bu/ac. That can be a big swing. That is why we don’t get too excited about what we are counting until it is in the bin. While it is fun to try and see what’s out there, each hybrid is going to be different and how the season finishes will determine the factor we use.