How to measure combine losses

August 28, 2013 - Issue 22

Combine loss pan, dropped_opt

Canola growers can lose up to 5 bushels or more per acre if the combine isn’t adjusted properly. Here are tips to limit those losses.

Step 1. Measure losses

Electronic loss monitors give you an idea whether losses are going up, but may not accurately tell you how many bushels per acre are thrown over. To calibrate loss monitors and to measure true losses out the back of the combine require a drop pan. Click here for an article with more detail on drop pan options.

How to take a sample

1. Disengage the chaff spreader and straw chopper and move them out of the way. That way, all straw and chaff drops straight down over the pan. This is important for calculations. Also, with the spreader off, the person holding the pan isn’t pelted with straw and seeds and dust if using a throw or stick pan.

2. Drop the pan, throw the pan, or hold the pan. When using the stick pan, the ideal is to move the pan into position upside down so it doesn’t gather any losses ahead of time. To position the pan, walk behind and to the side of the rear wheels and extend the pan so it’s in front of the chaff and straw discharge area. Once the pan is in position, quickly flip it over and stop walking. Stand still until the combine passes over the pan. With this procedure, you get the same result as though you’ve dropped or thrown the pan on the ground, but the handle gives you far more precision when it comes to placement. A long handle helps keep you out of the dust.

3. Remove the straw and chaff and preserve only the seed. A screen works. Another method is to put the collected sample in the bottom of a deep pail and stick a blower or old hairdryer into the pail. Chaff and straw will blow out and leave the seed behind.

How to calculate loss per acre

1. Measure the seed in the pan, by weight or volume. You need a scale that can measure in increments of 0.1 of a gram. You can also use volume or make a visual estimate. For more on these options, click here for a link to the Combine Seed Loss Guide.

2. Calculate based on one square foot. If your pan is two square feet, for example, divide the weight by 2 to get the total for one square foot.

Combine seed loss CF table_opt3. Determine the concentration factor for your combine. This is a ratio of header or swather width and combine discharge width. For example, if the swather is 30 feet and the discharge width is five feet, then the CF is “6.” See the table to the left to calculate your CF.

4. Plug these numbers into the Weighing Method table below to get losses in terms of pounds per acre. For example, if the loss per square foot (cleaned) amounts to 6.2 grams and the combine CF is 6, this converts to a loss of 100 pounds per acre — or two bushels per acre.

5. Take another sample before moving on to steps 2 and 3.

Combine seed loss Weight conversion_opt

Step 2. Determine whether those losses are acceptable

Combines running efficiently will lose some grain. If your target is zero losses, you’ll probably end up running too slow to get the job done in a timely fashion, risking shattering losses and cost increases that will outweigh any reduction in grain loss.

With canola, a three to five bushel/acre loss is fairly common. On a 40 bushel/acre canola crop, a three to five bushel loss represents 7.5% to 12.5% of the potential yield. Reducing those losses can provide a significant boost in profit. A properly adjusted combine going at a reasonable ground speed should be able to achieve a 0.5 to one bushel/acre loss.

Step 3. Steps to reduce loss

See the top 10 list in this issue of Canola Watch.

Link to:

Canola Watch