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Estimating Wheat Yield (07/13/17)

For early-planted wheat, there are several methods for estimating yield based on yield components.

Estimating Wheat Yield

For early-planted wheat, there are several methods for estimating yield based on yield components. One used by the Wheat Quality Council’s spring wheat tours for many years estimates yield using the number of spikes per area, the number of kernels per spike, and kernel weight. Since kernel weight cannot be precisely determined until harvest, the formula described below uses a historic average to estimate kernel weight prior to harvest. The value 0.142 is a constant that incorporates kernel weight and unit conversion factors. Since small differences in the numbers used in the formula can result in large differences in estimated yield, multiple samples taken from representative areas of the field will improve the accuracy of the yield estimate.

 Bushels/acre = (spikes per 3 ft. of row X spikelets per spike X kernels per spikelet X 0.142)

Row spacing (in.)

To calculate the values for this formula:

  1. Count the number of spikes in a three-ransomfoot length of row. Do not count small heads that will not significantly contribute to yield. If the crop was air seeded in bands or paired rows, count the number of spikes from the entire width of the band, or both rows in the pair.
  2. Count the number of spikelets in six or more randomly selected spikes. Omit the top and bottom spikelets because they contribute little to yield.
  3. The number of kernels per spikelet can be determined by hand threshing the head, counting the number of kernels, and dividing the number of kernels by the number of spikelets. Previous experience has shown that 2.3 kernels per spikelet gives an accurate yield estimate.  If the crop has experienced stress, use 2.1 kernels per spikelet.
  4. Determine row spacing by measuring the distance between several rows or bands of wheat. Most double disc drills are set at 6, 7, or 8 in. row spacings. The width of air seeded bands can vary significantly. To determine the row spacing of the bands, measure the distance between the edge of one band to the same edge of the adjacent band.

 

Examples from research plots in Prosper:

Winter wheat

(113 spikes in three foot row X 15.3 spikelets per spike X 2.3 kernels per spike X 0.142)/(7 inch row spacing) = 81 bu/acre

 

Spring wheat earliest planted (4/13/17)

(94 spikes in three foot row X 14.3 spikelets per spike X 2.3 kernels per spike X 0.142)/(7 inch row spacing) = 63 bu/acre

 

Spring wheat latest planted (4/22/17)

(93 spikes in three foot row X 12.3 spikelets per spike X 2.1* kernels per spike X 0.142)/(7 inch row spacing) = 48 bu/acre

*This assume fewer kernels will fill per spike due to stress.

Joel Ransom

Extension Agronomist for Cereal Crops

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