Charley Sprenger, Prairie Agricultural Machinery Institute
Today’s combines are well designed to minimize threshing losses when harvesting soybeans; however, there can still be significant losses at the header (accounting for 80% of the losses), particularly in Manitoba where the pods grow closer to the ground. Large combines currently being used in Manitoba will not be loaded to their threshing capacity in soybeans with headers used in canola and cereals. The header loss becomes the limiting factor to combine efficiency. Prairie Agricultural Machinery Institute (PAMI) has conducted several field-scale research projects to determine which factors affect header losses most in order to provide producers with management strategies for reducing risk by minimizing losses. Significant savings can occur if harvest losses are minimized.
Four variables, which may significantly affect header losses, are the type of header (draper or auger), the angle setting of the header (as per recommendations for a specific crop type), the use of an air system, and ground speed during harvest.
Type of Header (Draper or Auger)
Header type may make a difference in reducing losses. When properly adjusted (e.g. bean setting), a draper header has been shown to have less losses than an auger header (0.5 to 1 bu/ac difference). This is likely due to the conveying method; the draper allows a smoother flow of material to the feeder house and pods are less likely to shatter.
Angle Setting of the Header
Header settings are important for minimizing losses because of the proximity of the end of the bottom pod to the ground. An improperly adjusted draper header (e.g. when the same settings used for cereal crops are also used for soybeans) can have the highest losses (up to 1.5 bu/ac greater losses than when properly set to manufacturer’s recommendations). It is important to spend the time adjusting the header angle settings between crops to minimize losses regardless of the header type. One of the keys is getting the knife positioned between the ground at the lower tip of the bottom pod.
Use of an Air System
An air system has been found to have a significant effect on decreasing header losses for both header types. Losses can be reduced an average of 0.5 to 1 bu/ac when using an air system on either a draper or auger header. At a price of $10/bu, this can provide a savings of $5 to 10/ac. When trying to determine if an air system is worth the investment, consider that the payback area for an air system with an average capital cost of $16,500 would be 1,650 to 3,300 acres. This indicates that using an air system can provide substantial benefit in reducing losses.
Ground Speed During Harvest
The effect of ground speed needs to be weighed against the urgency of harvest. Ground speeds of 3 and 4 mph typically have lower losses than the higher tested speeds of 5, 6 and 7 mph with an average difference was 0.5 bu/ac. One of the studies, however, was inconsistent and found that there was no significant difference between losses at different speeds. It appears that crop and other environmental conditions are the likely causes of this varied result. This reinforces the recommendation that checking losses in each crop during harvest is the surest way to minimize them.
Assess Harvest Losses
Because of the many factors that can influence losses, it is important to understand header setup and operating effects. Producers can measure their header losses by counting the number of seeds on the ground in a 1 ft2 area. Stop randomly in the field and count between the header and the rear wheels of the combine; repeat a minimum of five samples randomly behind either side of the header to get a good picture of the losses. Four beans per ft2 = 1 bu/ac loss. Be sure to include loose seeds, seeds in pods, and seeds in pods on cut stubble or lodged stalked in your counts. Seed on cut stubble can indicate that the header is not cutting low enough. Lodging may indicate that the ground speed is too high and just pushing over plants.
The remaining factor that has been observed as having a potential impact on losses is the time of day that harvest occurs, which represents a combination of temperature and humidity. PAMI hopes to conduct another research project to address this remaining question that producers have. Hopefully, that will indicate if there is value in starting an hour later in order to reduce losses? Or, similarly, should the combine slow down more as harvest runs late into the night to reduce losses?
From all of these insights gained over several projects, producers can evaluate the value of a draper header, an air system and optimal travel speed for their operations, based on the return per acre of soybeans grown.