A few beans on the ground may not look like much, but small harvest losses can add up quickly across a Missouri soybean field.
By September, Missouri soybean growers have spent months protecting yield. They planted it, sprayed it, scouted it and watched the weather either cooperate or refuse to play along. Once the combine enters the field, most of the season’s decisions are behind them, but there is still money to make or lose in how efficiently that crop comes out of the field.
University of Missouri Extension estimates that four to five soybeans per square foot left behind equal roughly one bushel per acre. That may not sound dramatic until those beans are scattered across 500 or 1,000 acres. A loss that is hard to see from the cab can become a sizeable number by the end of harvest.
Start at the Header
Most soybean harvest losses happen at the front of the combine, which makes the header a good place to start when something does not look right. Mizzou Extension estimates about 80% of soybean harvest losses occur at the header.
Cutting height matters more than many growers might expect. Missouri research comparing cutter-bar heights found very little yield loss with a 2-inch cutting height, but losses climbed as the cutter bar moved higher. Researchers measured 0.3% loss at 2 inches, 2.6% at 4 inches and 9.5% at 6 inches.
Field conditions will determine how low a grower can safely cut. Rocks, rough ground, residue and uneven terrain all come into play. Short plants and low pods can make the decision even more important because a few inches of extra stubble may leave a surprising amount of the crop behind.
Lodging creates another challenge. A header moving too fast or set poorly for field conditions may push plants ahead, clip pods or fail to pick up plants lying close to the ground. In those fields, a little less speed may put more beans in the grain tank.
Moisture Can Cost You, Too
Soybeans can move through moisture levels quickly during harvest. Waiting too long may mean drier grain, but it can also increase shatter as pods become brittle and beans hit the ground before they reach the combine. Mizzou Extension also notes that harvesting very dry soybeans during periods of higher humidity can help reduce shatter losses.
Very dry soybeans bring another concern. Growers are selling pounds, and beans harvested well below standard market moisture carry less water weight across the scale. The field may yield the same number of beans, but those beans can weigh less when they are exceptionally dry.
Humidity changes during the day can also affect harvest conditions. A field that shattered badly during a hot, dry afternoon may behave differently later in the day as humidity rises. That makes harvest timing another management decision rather than simply a race to cover acres.
Check What the Combine Leaves Behind
Yield monitors tell growers a great deal, but they cannot replace getting out of the cab and looking at the ground.
Before the combine passes, check for beans that were already on the soil surface so natural losses do not get blamed on the machine. After the combine moves through, look for loose beans, intact pods, missed plants and beans coming out the back. A quick count across several spots can tell you whether the loss is insignificant or worth making an adjustment.
If losses are higher than expected, change one thing at a time. Ground speed, reel position, cutter-bar height, rotor or cylinder settings, fan speed and sieve settings can all affect harvest performance. MU Extension recommends making one adjustment at a time so growers can identify which change actually improves performance.
Conditions will change throughout the day, and settings that worked in the morning may not work as well several hours later. That is one reason a few minutes spent checking behind the combine can be worth more than trying to gain another acre or two per hour.
By harvest, growers cannot change the rain that fell, the heat that arrived at pod set or the disease pressure that showed up in August. They can still control how much of the crop they worked all season to produce makes it into the bin.
