Measuring harvest loss – common questions

August 14, 2019 – Issue 20

Here are some common questions from canola growers who are wanting to measure their losses at the combine.

Why should I check for losses? Canola harvest losses can realistically be as high as five bu./ac., and are commonly around one to two bu./ac. This is anywhere from 10 to 50 times higher than average seeding rates. Not only does this reduce profit margin and yield, but it contributes significantly to the weed seedbank, creating volunteer issues for years to come.

The recommendation is to drop straw when checking losses. Is this necessary? For the most accurate measurement and to reduce sampling error, the chopping and spreading mechanisms should be removed or disengaged. Internal choppers do not need to be removed.

Some producers have concerns that lifting the chopping and spreading mechanism out of the way will impact airflow through the machine, and therefore change losses. It is certainly possible that it will to a small degree, but keep in mind that we are not looking for precision accuracy with loss checks (and losses are not static). The benefit of capturing all losses by dropping straw typically outweighs the issue of impacting airflow. We encourage producers to check both ways if they are not convinced of this.

There are certain set ups where it is nearly impossible, or too time consuming, to remove/disengage chopping and spreading mechanisms, like set ups with chaff spreaders, for example. When checking losses while spreading, multiple samples need to be collected and an average taken. Sample right and left of the stream, and right down the centre.

Keep in mind there is inherent risk with being behind the machine while it is chopping and spreading.

What is the ideal pan size? (Does it have to cover the whole discharge width?) Pans do not need to be exactly the width of discharge. Smaller pans can be used for more accurate diagnosis of where losses are coming from (right side, left side, rotor stream, chaff stream). The larger the catch area, the more representative the catch will be – as losses are not static across a harvested area. But the larger the collection, the more difficult it becomes to screen and separate the seed.

What is the best way to separate seed from chaff in the drop pan? This can be done by hand, but it can be time consuming. Canola screens or an airstream to lift chaff is best. Bushel Plus produces a blowing/screening device for this purpose.

How often throughout harvest do I have to check for losses?Checking once is better than not checking. Checking regularly is best. Ideally, check every time there is a significant difference in crop and / or environmental conditions and any time settings are adjusted. Do the most thorough checks and adjustments at the beginning of harvest.

Further reading:

Canola Watch