Soybean harvest losses typically range from 1 to 2 bushels per acre under good harvest conditions representing approximately 2-4% of total potential yield, according to Joe Gleim et al. and Gary Huitink. Although this may seem insignificant, harvest losses can be much higher when soybean plants are short with low hanging pods, lodged, have green or tough stems, or contain brittle pods due to harvest delays. This article provides information about the causes of soybean harvest losses and practical recommendations for reducing them.
Total harvest losses come from three sources: pre-harvest losses, gathering losses and separating/cleaning losses. Gathering losses occur whenever loose soybeans, detached soybean pods or pods attached to uncut or cut stems are not picked up by the combine and left in the field.
Pre-harvest losses refer to all losses that occurred in the field prior to harvest. There are several causes of pre-harvest losses but the most common are hail damage after the plants have reached physiological maturity and harvest delays caused by a variety of factors.
Separating/cleaning losses happen inside the combine where the beans are threshed from the pods and all or most of the chaff (stems, threshed pods and leaves) is discharged from the back of the combine. Separating/cleaning losses typically occur when the amount of plant material entering the combine exceeds its separating and cleaning capacity. Common causes are very high yields, excessive ground speeds, slug (uneven) feeding, and wide headers that are not properly matched to the capacity of the combine. Worn or damaged separating parts and improper combine adjustments can also cause separating and cleaning losses. Most combines are equipped with grain loss monitoring technology designed to detect changes in separating and cleaning losses.
Gathering losses account for nearly 90% of total losses, according to Gary Huitink. Because gathering losses are responsible for most of the total harvest losses, most of the recommendations provided in this article are focused on reducing gathering losses.
Crop conditions that increase gathering losses
Shattering
Shatter losses occur when harvest operations cause the pods to open and loose beans fall directly on the ground or on the grain table but fail to enter the combine. Shawn Conley and Laura Lindsey identified drought conditions during the growing season and repeated wetting and drying cycles occurring after the beans initially dry to 13% moisture as frequent causes. Low moisture levels in the seed (less than 11%) at the time of harvest is also an indicator that shattering is likely to occur. Spider mite feeding has also been shown to make soybean pods more brittle and prone to shattering. Photo 1 shows volunteer soybean plants sprouted from unharvested beans.
Lodging
Lodging occurs when the plant stems cannot hold the plants upright and they lean or fall over. This can increase harvest losses and slow harvest operations. Abundant rainfall or irrigation water applications during the vegetative growth stages are the primary environmental conditions leading to lodging according to William Kranz and Jim Specht. These conditions produce taller plants that have longer internodes. Lodging causes harvest losses because the cutter bar rides over leaning plants leaving uncut plant parts in the field. The following management practices can reduce the potential for lodging to occur:
Planting varieties resistant to lodging .
Planting at low to moderate seeding rates.
Maintaining adequate potassium soil test levels.
Avoiding applications of nitrogen fertilizer or livestock manure prior to planting soybeans.
Green stem syndrome
Green stem syndrome is a condition that causes the plant stems to stay green even after the pods and seeds are fully mature and have dried to acceptable moisture levels for harvest. Although certain viruses and foliar fungicide applications have been associated with green stem syndrome, the most frequent cause is physiological according to David Holshouser. Dry conditions existing during pod set and early seed development followed by adequate rainfall favor the development of green stems. The plant leaves produce more carbohydrates through photosynthesis than the reduced number of developing seeds can utilize, causing them to remain in the stem.
Farmers don’t like harvesting plants with green stems because they significantly slow harvest operations, increase fuel costs and can cause the combine to become clogged with green plant material. Delaying harvest causes the pods to undergo repeated wetting and drying cycles, making them brittle and prone to shattering.
Source: msu.edu
Photo Credit: istock-ds70
Categories: Michigan, Crops, Soybeans