Soybean Harvest Considerations

 

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 beginning to turn and in some shale areas were already a mature brown coloration. 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, more than 5 times that of corn. So dry down is quick. The data also suggested about 12 days after pod maturation 13% moisture was noted over the study period. For more information visit Iowa State University, 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. Figure 1 is a picture of our crop teams’ soybean planting date study. Same variety, same seeding rate, same pest management program, the only variable was the date of planting in these plots from March 28 to May 28. 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 versus varieties that tend to layover 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 (Table 1). 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.

 

 

Harvest Delay	Year 1	Year 2	Year 3	3-year Average
None	4.1	6.7	7.5	6.1
2 Weeks	5.0	9.9	9.2	8.1
4 Weeks	6.3	16.1	12.1	11.5
6 Weeks	6.8	18.1	19.9	13.9
Average	5.6	12.7	11.4	9.9

Source: University of Wisconsin

 

If you assess the discount for bringing soybeans in a little wetter than normal there will be some cost drop in the beans. In Table 2, 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.

 

 

 

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 go to 5 inch height of cut and that jumps to 10% loss. The following suggestions will help keep these losses to a minimum.