A Tale of Two Cornfields.

A look at some corn in August.

First the bad news. Here is a look at a typical ear from Over East (the field with the hail damage.) The obvious thing to notice is the huge amount of tip-back on this ear. The plant has basically "cut off" these kernels from the nutrient supply in response to its loss of leaf area. Tip-back is quite normal and something you actually want to see in the field. It usually isn't so pronounced, however. Why do you want to see it? Tip back is the final adjustment the plant makes based on the stress it is undergoing in the field. A little bit of tip back is evidence of a healthy plant population. Remember our goal is yield per acre, not yield per plant. A field that has minimal tip back is an indication that the plant population is too low and that there is yield potential not being realized. The excessive tip back on this ear indicates the severity of the leaf loss from hail.

Here are a couple of examples of ears which took direct hits from hailstones. The damage is pretty self explanatory.

Another problem which the direct strikes create in addition to the primary damage to the ear itself is a separation of the husk surrounding the ear. On this ear you can see the beginnings of a infection of the ear due to the direct exposure to water and air.


Now lets look at some good corn. Here is a typical ear from home. Notice the tip-back on this ear. Perfect.


Here is a look at two different ears which set on a different number of kernels. The corn plant determines the amount of kernels per ear at a very early stage (between v6 (i.e. 6 leaves on the plant, or ) and v8( this is when the plant is between say 6" and 2' tall.)) Various reasons exist for the number of kernels the plant set, including genetics, nutrients, moisture, population etc. etc. Basically the little plant "makes a decision" about the environment it is in and "plans" accordingly. As you can see, the cob above has 16 rows, while the cob below has twelve. While there is no magic number, generally the more rows the better. I like to see most ears in the field at either 16 or 18. As you can see, however, the plant can still make some pretty good corn off of a smaller ear too. Look at the size of the kernels on the ear below!
Looking down at the leaves we can see some of the results of our fertilizer program. Of course you remember that I played around with some manure this spring. Unfortunately, it looks like I either underestimated the amount of available Nitrogen from the manure or that this field wants to yield more than I "gave it credit for." With the nice "cool" summer we had it may just be the latter. This yellowing pattern on the lower leaves is a classic indicator of Nitrogen deficiency. It is caused by the plant mining nitrogen from the older leaves in order to support grain fill. This late in the season, there is pretty much nothing that can be done. How much yield is being lost? It's anybody's guess, but we may be able to get a good idea once we talk to the neighbors after harvest.