Estimating Harvest Losses in Cereals – Don’t Just Rely on the Grain Loss Monitor!


Winter wheat and fall rye harvest is underway in Manitoba. Since final yields aren’t determined until the crop is in the bin, attention now has to be focused on the harvest operation. Grain loss at harvesting time is a direct loss of income. The more grain saved, the greater the returns. The following information comes from 2 articles: ‘Grain Harvest Losses’ by V. Hofman with edits by Dr. J Wiersma & T. Allrich (University of Minnesota) and ‘Estimating Harvest Loss’ by G. Carlson & D. Clay (South Dakota State University).

Grain harvest losses result from shattering of the standing grain, shattering during windrowing (swathing) or direct combining, picking up the swath with the combine, and threshing, separating and cleaning within the combine. Estimates of acceptable losses for small grains such as wheat, barley and oats are placed at 3% of total yield (total yield equals harvested yield plus harvest losses).

It is usually very difficult to reduce total losses below 1 to 2% so the operator must decide on the value of the crop, the cost of combining and the time available for combining or climate conditions. Some harvest loss is unavoidable in order to get harvesting done in the time available with an end goal of cleaned harvested grain.

Estimating Harvest Losses.  Advancements in engineering have greatly improved harvest operations. Combines have various types of monitoring equipment available, including grain loss monitors, to help alert the operator to any potential problems.  A grain loss monitor is a good guide in selecting travel speed for varying conditions such as size of windrow and moisture conditions. A grain loss monitor must be calibrated to provide an acceptable grain loss reading. If the combine is used on different crops, the monitors are not only useful in limiting maximum speeds and losses, but can be used to properly feed the combine for optimum capacity.

However, a grain loss monitor is not a substitute for careful machine adjustments and good old fashioned monitoring, i.e. getting out of the combine to estimate losses. Or even better, when your local retail agronomist comes out with cold beverages, put him/her to work to estimate harvest losses.

A simple and rough estimate of grain loss requires the use of a one-foot square frame. A rough estimate of how much grain is left behind in a harvested field can be done with a few simple steps:

  1. Pick a typical area of the field after the combine has passed.
  2. Place a 1 ft by 1 ft (inside dimension) box on the ground and count the kernels found within the box. To improve accuracy, three counts (one behind the left side of the header, one behind the centre of the combine, and one behind the right side of the combine) are better.
  3. A one (1) bushel per acre loss equates to 20 wheat kernels/ft2, 14 barley kernels/ft2 and 10 oat kernels/ft2. Keep in mind that this is a ‘fudge factor’ but for the purpose of rough field estimation is an adequate estimate. There are more accurate ways to estimate harvest losses which take into consideration the width of windrower cut and combine cylinder.

If losses are on the high end, some investigation is warranted to try and identify the source of loss.  Is the crop shattering prior to the arrival of the combine (to check for losses that occurred prior to the arrival of the combine, i.e. shattering, use the method above in the unharvested areas of the field)? Are there header losses? Or are the losses due to less than perfect threshing/separation of grain within the combine?  Finding the answer may help to adjust the harvest operation and maximize the amount of grain going into the bin!

Good luck with #Harvest16!

Submitted by: Pam de Rocquigny, Provincial Cereal Crops Specialist, Manitoba Agriculture

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