Share:

**ears per acre**, number of **kernels per ear**, and average **weight per kernel**. Though the first two components may be evident three weeks after silking, the weight per kernel is unknown until five or six weeks later. This is because kernel depth and density (test weight) continue to increase until black layer. Consequently, early estimates have to account for kernel weight by using a broad average. This kernel weight component contributes most to yield estimate variability, especially if growing conditions deviate from normal after the estimate, or a hybrid's intrinsic kernel weight is much higher or lower than average.

**a variable field can be split into two or more fields** if the borders of non-uniform areas are clear and the size of each part can be easily determined.

**General Procedure** (see details below.)

- Sampling Intensity:
- In uniform fields, conduct 5 to 8 individual samples, or about one sample for every 10 to 15 acres.

- In non-uniform fields, conduct 8 to 12 individual samples, or about one sample for every 6 to 10 acres.

- In uniform fields, conduct 5 to 8 individual samples, or about one sample for every 10 to 15 acres.
- Choose each sample location at random.
- For each sample, measure 1/1000 acre.
- Count
**number of ears**in each 1/1000 acre sample. - Count
**kernels per ear**on 3 ears from each 1/1000-acre sample. - Average the
**number of ears**across all sample locations of the field. - Average the
**kernels per ear**across the 3 ears of each sample and across all the sample locations of the field. - Multiply
**number of ears**x**kernels per ear**x 1000. - Divide the answer from step 8 above by number of kernels per bushel to get bu/acre (at 15.5% moisture).
*See step 9 in section below for more explanation.*

**Sampling Intensity**should be commensurate with the purpose of the yield estimate and time available. Determining if a field is uniform or non-uniform and whether to split a field into two or more fields will have a large impact on the accuracy of the overall field estimate.**Choose a sample location.**Use a pre-determined method to avoid bias when picking a sample spot in the field. For example, walk 20 paces into the field and begin exactly there.**Measure 1/1000 acre.**Use a tape or pre-measured rod to measure 1/1000 acre. For**30-inch rows,**1/1000 acre = 209 inches (**17 feet 5 inches**).For other row widths, divide 6273 by the row width. For example, for 36-inch rows: 1/1000 acre = 6273/36 = 174 in. = 14 ft. 6 in.

**Count number of ears per 1/1000 acre.**If there are two ears per plant, count them both. But do not count “nubbin” ears that have less than 5% of the kernels of normal ears.**Count kernels per ear on three ears from each 1/1000 acre sample.**Pick the three ears using a pre-determined procedure to avoid bias. For example, take the 5th, 15th, and 25th ears. Do not use nubbin ears that were not included in the ear counts. (For greater accuracy, you may sample and count kernels on more than 3 ears. For example, use five ears or six ears.)

It is likely easiest to count number of rows and number of kernels per row and multiply to arrive at kernels per ear. With irregular ears such as pinched ears or drought-stressed ears, you may need to adjust that process. Do not count aborted kernels that will contribute little to yield.**Average the number of ears across all sample locations of the field.**Simply add the number of ears in all samples (from step 4 above) and divide by the number of samples.**Average the number of kernels per ear.**Simply add the number of kernels from all ears for which kernels were counted (from step 5 above) and divide by the number of ears for which kernels were counted.**Multiply number of ears x kernels per ear x 1000.**Multiply the average number of ears by the average number of kernels/ear (from steps 6 and 7 above). Multiply this number by 1000 to get number of kernels per acre.**Divide the answer from step 8 by number of kernels per bushel.**For example, the broad average for number of kernels per bushel is 90,000. Divide the answer from step 8 by 90,000 to get average bu/acre for the field (at 15.5% moisture).*90,000 may not be the best number to use – see section below to help determine the best number.*

Univ. of Illinois. 2005. Estimating corn yields (an online calculator.) Illinois Agronomy Handbook.