With the ongoing heat and drought conditions in much of Kansas, many corn growers are trying to decide if their corn crop is worth keeping for grain harvest or if it should be harvested for silage or left in place for residue benefits.
Where tassel, silking, and pollination are complete, or nearly complete, producers can begin to get some idea of what the potential yield might be. To get a reasonable yield estimate, corn should be in the milk, dough, or dent stage. Before the milk stage, it is difficult to tell which kernels will develop and which ones have been aborted.
Producers can get some estimate of the success of pollination by examining ear silks. With successful pollination, the exposed silks should be turning brown and should easily separate from the ear when the husks are removed. Silks that have not been successfully pollinated will stay green, possibly growing to several inches in length (Figure 1). Unpollinated silks also will be connected securely to the ovaries (the undeveloped kernels) when the husks are removed.
Figure 1. Long silks primarily reflecting floral asynchrony. Silks that have not been successfully pollinated will stay green. Infographic by Ignacio Ciampitti, K-State Research and Extension.
Estimating corn yield
Yield estimates can be made using the yield component method. This method uses a combination of known and projected yield components of corn to calculate an estimate of the potential yield. It is “potential” yield because one of the critical yield components, kernel size, will not be known until physiological maturity. Before then, one can use only an estimate of predicted yield based on what you think the grain filling period might be like (e.g. favorable, average, or poor). Estimating potential corn yield using yield components uses the following elements:
Ears per acre: (30-inch rows)
Kernels per ear:
Kernels per acre:
Kernels per bushel:
Bushels per acre:
If these estimates are close to correct, the field in this example is probably worth taking to grain harvest provided it is still living and likely to keep filling grain. Past experience indicates that this method of estimating yield usually provides fairly optimistic estimates. Use a larger number for kernels per bushel if you want the process to be a bit more “pessimistic.”
See the June 25, 2018 Agronomy e-Update Issue 699 , “Management options for stressed corn”, for the range of yields that might lead to a decision to chop the crop for forage or maybe even leave it in place for the value of the residue.
More information on stressed corn and related topics:
Further details on corn growth and development can be found at: http://www.bookstore.ksre.ksu.edu/pubs/MF3305.pdf
Links with further discussions on the yield estimation:
Ignacio Ciampitti, Crop Production and Cropping Systems Specialist