Estimating Your Corn Yield

This means the starch content of the kernel is increasing and the kernel is hardening from the outside in. This is actually a process that we can watch happen by watching the “milk line” of the kernel move from the top of the kernel to the tip. When dent stage starts it typically takes a 12-18 days for the milk line to finally finish at the tip of the kernel. Folks who chop silage typically are looking for the ½ to ¾ milk line stage to chop, as this indicates the proper moisture of the crop to be stored.
 
This stage is also a great stage to start estimating yield because 3 of the factors have been set for a while now;  the kernel rows, kernels per row, and the number of harvestable cobs in an acre. But waiting until now will give you a good idea of the 4^th factor as well, which is test weight. Because the weather has been quite favorable during grain fill in most of our area, this will change the factor we use for test weight, and you will see that in my calculation shortly.
 
The first thing to do is count the number of cobs in 1/1000^th of an acre. To do this on 30” rows, mark off a row area of 17’ 5” for 22” rows mark off 23’ 9” once done count the number of harvestable ears in that row space, this will give you your total plants per 1/1000^th of an acre. You may want to do this in several different areas and get an average. Don’t be surprised if there are less ears than the population you planted at, with the dry weather during spring/early summer, corn emergence was variable due to lack of moisture. Once you have your average number of ears, get 3-4 average ears and count the number of kernels per row and rows per cob. Get an average count again and now comes the calculation.
 
Your field produced 31 ears that were 16 around and 37 along
 
# Ears * # kernel rows * Kernels per row = # of Kernels
31*16*37 = 18,352 kernels
 
The fourth factor is test weight, typically we use a factor of anywhere from 80-95 to account for test weight (80,000-95,000 kernels per bushel) because of the weather conditions we will use a slightly better that average test weight. I will use 85 for the factor. Take your # of kernels and divide by the test weight factor.
 
# of kernels / test weight factor = bushels per acre
18,352 / 85 = 215.9 bushels per acre

Jackson Gregory 
Belgrade Cooperative Agronomist