Some farmers won't have to worry about tip abortion or poor pollination this year in Indiana. They got crops in early enough that they got a break on weather, with their pollination occurring before the longest-hottest streak in over 70 years set in. Many others, however, weren't as fortunate.
Where there are problems, crops consultants and others are talking about various types of yield loss. In some cases pollination may have been affected, and kernel set throughout the cob may not be as precise as usual. What most people are talking about, however, is tip dieback, caused by abortion of corn kernels. The ear pollinates and fills the butt kernels first, them moves toward the tip. If conditions are rough by the time it reaches the point where it should fill those end kernels,. The plant may opt to preserve the kernels it already has so it can produce viable seed. It doesn't know that commercial corn won't be replanted. To the corn plant, its' job is to make as many babies as possible, not ot produce as much yield as possible.
Calculating yield in the field is the way to see how much tip die back and aborted kernels can affect corn yields. The formula for figuring relative yield is based on the one used in the Purdue University Corn and Soybean Diagnostic Field Guide, produced annually by the Purdue Crop Diagnostic and Training Center.
The basic formula to estimate yield of standing corn in the field is to mark off 1/1000th of an acre. In 30-inch rows that's roughly 17 feet, five inches. Nest record the number of harvestable ears per 1/1000th acre. Some people to prefer to do two rows side by side to get a larger sample size. This entire procedure should be repeated at several locations selected randomly within the field to produce a field estimate.
On every 5th ear, count the number of rows of kernels and number of kernels per row. Multiply the two numbers to get kernels per ear. Average your ear counts for kernels together. Then multiply average number of ears by acreage number of kernels per ear. In older versions fo the guide, the instructions said to divide by 90. The 2011 edition suggests different factors based on different conditions. For example, divide by 75 to 8 for good conditions, 85 to 90 for average conditions, and 95 to 105 for poor conditions.