Minimize Soybean Harvesting Loss and Maximize Cost Per Bushel

Over the last several years of working with what I consider the top soybean producers in Lebanon County I have learned the importance of timely harvest of soybeans. This week I noticed late group 2  beans were approaching harvest moisture. It has been my experience that once 95% of the pods turn brown about a week later it’s time to combine. Some recent work at Iowa State showed a 3.2% loss of moisture per day, which is more than 5 times that of corn. So dry down will occur quickly. The data also suggested about 12 days after pod maturation 13% moisture was noted over the study period. You can read more about the Iowa State dry down study at "How Fast do Soybeans Dry Down in the Field?"

Once moistures dip below 13%  a grower is essentially giving the mill soybean dry matter since they will correct the moisture to 13%. I still remember John Yocum referring to the fact that after the plants first reach harvestable moistures, dry matter losses occur simply by the alternating day night and heavy dew. It is important to consider the variety since some varieties will have slight differences in the pod integrity and not tend to split as the heavy dew at night can speed up this process. There are also impacts of erect varieties that might tend to dry quickly and delays in harvest may impact those, compared to varieties that tend to lay over and nestle protecting large fluctuations in dry down.

Numerous tests of soybean combine losses show that up to 12 percent of the soybean crop is lost during harvest. Harvesting losses cannot be reduced to zero, but they can be reduced to about 5 percent. Combines can be operated to reduce losses without affecting the harvesting rate. This guide describes the major sources of loss. Consider shatter losses of 2 percent acceptable. Average losses are 5 percent or more.

If you assess the discount for bringing soybeans in a little wetter than normal there will be realized return in both less shatter loss and more income. In the following table you will note the relative cost per bushel of soybeans to be around 30 cents. This is a cost that is easily overcome by the reduced harvest loss in the field at current market prices.  It appears that soybean dryer than 13% return about the same to management but this does not take into account the penalty of shatter loss in the field. You can check your own mills by changing the discounts and market price here. Simply download the soybean discount table.

Tips for keeping combine losses low

There are combine heads that force air back into the platform to assist in reducing harvest as well as other types of heads. However there are some simple rules to follow. I found the following excerpts from a Missouri article useful during harvest to capture the losses that may occur during harvest.  (Missouri Department of Agricultural Engineering)

Your best guide for correct combine adjustment is your operator’s manual.
Remember that more than 80 percent of the machine loss usually occurs at the gathering unit. The height of the cutter bar directly impacts what beans get into the bin.  If I were to harvest pods by hand versus as little as a 3.5 inch height of cut that would equate to a 5% loss just from the cutter bar height. Increase to 5 inch height of cut and that jumps to 10% loss. The following suggestions will help keep these losses to a minimum:

• Make sure that knife sections, guards, wear plates and hold-down clips are in good condition and properly adjusted.
• Use a ground speed of 2.8 to 3.0 miles per hour. To determine ground speed, count the number of 3-foot steps taken in 20 seconds while walking beside the combine. Divide this number by 10 to get the ground speed in miles per hour.
• Use a reel speed about 25 percent faster than ground speed. For 42-inch-diameter reels, use a reel speed of 11 revolutions per minute for each 1-mile-per-hour ground speed.
• Reel axle should be 6 to 12 inches ahead of the cutter bar. Reel bats should leave beans just as they are cut. Reel depth should be just enough to control the beans.
• A six-bat reel will give more uniform feeding than a four-bat reel.
• Complete the harvest as quickly as possible after beans reach 15 percent moisture content.
• A pick-up type reel with pick-up guards on the cutter bar is recommended when beans are lodged and tangled.

Finally, If you would like more reading on this I would direct you to navigate to this Agronomy Journal Publication that address this issue in more detail.