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Grain Fill Will Determine Last 10% or More of Yield

Grain Fill Will Determine Last 10% or More of Yield
Crop Watch 2014: Choose factors that best represent kernel fill when estimating yields.

The year has been favorable in many areas for corn so far. Included in that general statement are areas where it's been slightly too dry, areas where there was ponding and lost stand early, but many areas that have received just the right amount of moisture.

All areas have experienced a cool summer. Cooler than normal, wetter than normal summers tend to produce more corn, and often more corn than USDA estimates in its first crop report this week.

Crop Watch 8/8: Field Check Finds Most Corn Ears Filled to the Tip

Crop Watch 2014: Choose factors that best represent kernel fill when estimating yields.

Where conditions have been favorable so far, the final leg to top yield is grain fill, notes Dave Nanda, consultant for Seed Consultants, Inc. "How deep kernels fill and the amount of starch packed into kernels can affect yield," he says. It can also affect test weight, with fuller, plumper kernels usually weighing more per bushel of volume than lighter or chaffy kernels more likely in drier conditions.

The Purdue University Corn & Soybean Field Guide, 2014 edition, features a method to estimate corn yields on pages 42 and 43. Be sure you use the 2014 edition. Here's why.

In earlier editions, as far back as 2003, the Guide used a formula where number of ears per acre times number of kernel rows times number of kernels per row were all multiplied together, then divided by a factor. The factor was based upon an average number of kernels per bushel. Earlier versions of the Guide always used 90 as the factor. If you use smaller numbers, you get higher yields. If you use bigger numbers, you get lower yields.

Crop Watch 8/4: A Field with Two Corn Hybrids: How to Figure Out Which is Which

Pick right factor: Which factor you should use as the divisor to estimate yields may be unclear now. It may depend on weather conditions throughout August.

The 2014 edition recognizes that modern hybrids can often vary on kernel fill, with many producing full kernels if conditions are right. So it lets you choose the factor for the formula. If you believe the fill will be excellent, you can use 75, or even a lower number, to divide by. If it is average, stick with 75 to 80. If grain fill is poor, use 85 to 90.

If grain fill is excellent and you use lower numbers, you will estimate yield at 20 to 30 bushels per acre more than if you use the standard factor of 90, now reserved for situations with very poor grain fill.

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