As of this writing, October 20th, over half of the soybeans and probably 75 percent of the corn remains to be harvested. The cool July weather that was pleasant from the aspect that we did not have any days with temperatures over 90 degrees meant that crop development lagged behind. We had some rain in August and September which helped finish what looks to be a pretty good harvest. Then came October. We have had an unprecedented run of cool wet weather that has really set back the 2009 harvest. The moisture was needed to recharge the soil moisture profile. But we are at a point now where we need to have some dry, warm weather to get the crop out of the field and get some tillage done yet this fall. We are not at a truly critical point just yet but it is fast approaching.
The big concern right now is getting the soybeans out of the field. Soybeans do not keep well in the field once they are mature. The recent weather that we have experienced, alternating dry and wet periods, can cause the soybean plants to start lodging and, in some cases, split the pods open. Once the beans are out of the pods and on the ground they are a total loss. On the other hand, because of the weather we have been experiencing, the soybeans have not been drying down in the field the way we have seen in recent years. Once we are past the middle of October they have to come out even if they are wet. We have to be cautious, if soybeans are harvested with moisture content over 13 percent, artificial drying is necessary.
So what do we do with wet soybeans? There are a couple of options. Soybeans with greater than 13 percent moisture are likely to mold under warm conditions. However, if the storage temperature is kept about 60 degrees, soybeans can usually be stored for at least six months (at 13 percent moisture) without mold problems. For storage in temperatures higher than 60 degrees or for periods of time lasting longer than six months, the recommended moisture content is 11 percent. Soybeans harvested at 11 to 13 percent moisture can be placed directly into storage bins equipped with simple aeration systems (perforated ducts or pads and relatively small fans).
Natural-air drying guidelines: Using unheated air to dry soybeans usually works well, but it's a slow process (two to six weeks, depending on initial moisture, airflow and weather). In southern Minnesota, we recommend using an airflow of 1 cubic foot of air per minute, per bushel (cfm/bu) to dry beans with 17 to 18 percent moisture, 0.75 cfm/bu for beans with 15 to 17 percent moisture, and 0.5 cfm/bu for beans with 13 to 15 percent moisture.
Low temperature drying guidelines: If cool, damp weather prevents soybeans from drying to 13 percent moisture, consider adding a small amount of heat to the natural-air dryers. However, do not heat the air more than 3 to 5 degrees or you will overdry the beans and possibly cause an increase in splitting. Research does show that exposing soybeans to relative humidity levels of less than 40 percent can cause excessive splitting. Another thing to remember is that we will see a lot of changing conditions throughout the days and weeks ahead. This makes it very important to monitor field losses behind the combine and adjust the combine accordingly. To estimate soybean harvest loss: To check for field losses, check an area of 10 square feet. 40 soybeans lost in this area will add up to one bushel of loss. The best way to get an accurate read is to look at several spots in the part of the field already harvested and measure off 10 square feet. Count the soybeans on the ground and divide by 40 to determine bushels per acre.