HOW TO ESTIMATE YOUR CORN YIELD BEFORE HARVEST.

To get an ESTIMATE of your corn yield, follow these procedures in at least 5 random areas of the field and then average the results:

1) Count the number of ears in 1/1000 acre. (17' 5" in 30" rows; 14' 6" in 36" rows; 13' 9" in 38" rows; 13' 1" in 40" rows.)

2) Figure the average number of kernels per ear on at least 3 ears in the 1/1000 acre chosen (No. rows x kernels per row). Do not count the small kernels at the tip of the ear and avoid bias in your selection by choosing the 5th, 10th, and 15th ear.

3) Estimated yield = (No. Ears in 1/1000 acre x kernels per ear average x 0.01116). For example if 25 ears were counted in the 1/1000 acre chosen and an average of 650 kernels per ear were found from the 3 ears chosen, the estimated yield would be 181.35 bushels per acre.

4) Average the results of the 5 random areas chosen.

* This method usually underestimates the yield of heavy test weight corn.

A BIG MISTAKE MANY PEOPLE MAKE IS JUDGING YIELD DIFFERENCES BETWEEN HYBRIDS BY EAR SIZE.

Often side by side corn hybrids are judged on the appearance of the plant or the size of the ear. What determines yield is the number of kernels produced per acre and the weight of those kernels. The only way to accurately estimate yields between two or more hybrids planted in the same field is to weigh each hybrid. This can be done across the scales, with a weigh wagon or with a combine monitor that measures mass flow. Monitors that measure volume will not be as accurate if test weight between hybrids differs significantly.

DON'T STOP IRRIGATING YOUR CORN TOO SOON!

Many growers have been lead to believe that the crop is made after corn reaches the dent stage. We still have about three more weeks of work left to do! The potential yield at first dent is only about 75 percent complete. Don’t leave money on the table. Continue to apply enough water to take the corn through the black layer stage. Kernels will accumulate weight until the black layer stage is reached. The black layer can be identified by scraping the surface layer off the base of the kernel on the flat side opposite the germ. The kernels on the butt of the ear will reach black layer last.

UNFILLED EAR TIPS MAY BE CAUSED BY POOR POLLINATION, ABORTION OF KERNELS, OR THE GENETICS OF THE HYBRID.

Distinguishing between the three causes of unfilled ear tips allows us to understand what happened. Remember, unpollinated ovules will simply be blank while aborted kernels are shrunken remnants of kernels.

1) Barren ear tips mean that the ovules were never fertilized. Silks from the ear tip are the last to emerge from the ear. Drought stress or extremely cool, cloudy weather may delay emergence of these silks until pollen shed is complete. In addition, certain insects may clip silks interrupting the pollination process or silks may dry out due to drought and high temperatures causing the silks to be non-receptive to the pollen.

2) Kernel abortion occurs in the blister or early milk stages. Kernels on the ear tip are very sensitive to stress. It is not unusual to see these kernels abort since they are the youngest and the farthest from the incoming food source. Occasionally, kernels may abort in 2 or 3 columns that run the entire length of the ear. Basically, any kind of stress that reduces the photosynthate supply may cause kernel abortion.

3) Genetics of the hybrids may also play a part in unfilled ear tips as some hybrids will not fill to the tip even in a non stress year, while certain hybrids most always fill to the tip.

COMMON SMUT IN CORN IS CAUSED BY THE FUNGUS USTILAGO MAYDIS.

This disease is very easy to identify, as it forms tumor-like galls which may vary considerably in size. The fungus overwinters in corn residue or in the soil. It is not unusual to see smut in a few scattered plants every year, however, yield losses from this disease are usually minimal. Injury from insect feeding, hail, sand blasting, etc. may promote smut damage as this allows entry for the fungus. Also, excessive nitrogen, unbalanced fertility and corn grown where heavy applications of manure have been applied may promote common smut. Common Smut is usually worse where stinkbugs have moved in from nearby wheat fields with damage being highest along the edges of fields. Smut spores are spread by wind, insects and animal manure. All above ground parts of the corn plant are susceptible to damage from common smut. Young plants infected by the fungus may be killed or have barren or smaller ears while infection in older plants usually results in loss of the ear.