Performing Yield Estimates
In late summer and early fall, many corn growers evaluate fields and make yield estimates either for corn storage or marketing purposes. Estimating yield can be difficult since weather conditions at various stages of growth can result in a highly variable crop appearance and differences in yield. Obtaining accurate yield estimates requires multiple samples throughout a field.
Estimate on a whole field basis
When conducting whole field yield estimates, the Yield Component Method is commonly used and is calculated by:
The number of kernels per bushel can be highly variable among hybrids and growing conditions. Typically, 90,000 kernels/bu is used as an average, though hybrid differences are known to vary by over 30%.
Perform estimates for each specific hybrid
Wyffels research has documented the number of kernels per bushel for each hybrid (listed on the chart, page 2). This factor has been updated with 2021 data with newly released hybrids. Not all hybrids have yield factor data available. Products from the same genetic family use the same yield factor. This factor can vary based on the growing conditions each year. Hot and dry conditions can cause smaller kernel size which increases kernels per bushel. These factors should serve as a good baseline for accurate yield estimates for each genetic family.
If seed set is scattered on the ear, the kernel size may increase thereby decreasing the number of kernels per bushel. In fields impacted by heat and drought or that have reduced stands, more samples will be needed to ensure reasonable representation of the entire field. This yield estimate is best done at least 2 weeks after pollination at the milk stage (R3) and beyond.
The exact number of kernels per bushel for each hybrid will vary each year based on crop conditions, but the differences between hybrids remain consistent. So, even in more variable conditions these serve as a great tool to see differences between hybrids when performing yield estimates.
Take Samples
Use the following protocol to ensure more accurate estimates.
1. Measure 1/1000th of an acre in one row (17’5” for 30-inch rows) and count the number of harvestable ears present.
2. Collect every 7th ear to get a representative sample.
3. Count and multiply the number of kernel rows around by the number of kernels in a row for each ear. For example: 16 kernel rows around x 34 kernels per row = 544 kernels/ear.
4. Average and record the kernel counts of at least 3-5 ears in each harvestable ear count to determine average ear size (kernels/ear) in that location. Do several harvestable ear counts across the field to represent all the conditions present. Ten or more locations may need to be sampled in a field that’s variable.
5. Plug in ear and kernel counts into the above formula to arrive at the estimated yield. Dividing by 90,000 kernels / bushel is an average that many growers use. For specific hybrids, use the factor listed below in the calculation.
This yield calculation uses actual harvestable ear counts, so low stand counts are accounted for in the estimation. An accurate ear count is very important for good estimates. Simply using the planting rate will overestimate yield.
Wyffels Yield Calculator
In order to make yield estimates easier and more efficient, Wyffels has developed an online yield calculator. The Wyffels Yield Calculator can be found on the Wyffels.com website under the Agronomy tab. This calculator has been pre-programmed with all of the specific hybrid factors for hybrids in the Wyffels lineup. To use the calculator, click this link.
What about Lodging?
If the field has evidence of root lodging, some additional calculation may be necessary to account for additional yield loss. Root lodging can reduce yields, but the stage of growth has an impact on the amount of actual loss. Root lodging at early vegetative growth stages (before V10-V12) may cause yield reductions of 0-5%. When root lodging occurs at R1 and beyond, yield reductions range from 10-30%. The actual yield lost by root lodging is impacted by weather conditions and other agronomic factors that occur after damage is present.
Stalk lodging can also cause yield loss. Some estimates indicate about 1/3 of stalk-lodged plants may be lost at harvest. Some of these losses may occur after a yield estimate is made. You may want to account for this possibility in your estimate.
Summary
Estimating yield can be difficult and variable. Increasing the number of ear samples and thoroughly covering the field will ensure the best estimates. Using the specific hybrid factor for each hybrid will help you fine tune estimates for your Wyffels products.