Farm Progress

Take these things into considerations before replanting corn or soybeans after field flooding.

Kent Thiesse, Farm management analyst and vice president

June 15, 2018

4 Min Read
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As has become typical in recent years, heavy rainfall events have occurred during the first two weeks of June, leaving some farm operators with difficult decisions with regards to replanting crops. Many locations in southern Minnesota and northern Iowa received several inches of rainfall during that period, which lead to considerable standing water and drown-out damage in fields. In addition, there was hail in some areas that damaged crops, which could also result in replant decisions, especially with soybeans.

Most producers will likely not be replanting corn at this late date, except for livestock producers who can use the corn as silage or high-moisture corn. Based on university research, corn planted in southern Minnesota during the period of June 5-10 has only about 50-60 percent of the expected yield potential, compared to corn planted in late April to early May. Corn planted later in June has even less yield potential. Soybean yield potential is also reduced with planting after June 1, but not as severely as corn.

Early varieties of soybeans that are planted in mid-June in southern Minnesota have a realistic yield expectation of 30-40 bushels per acre, compared to normal yields of 50 bushels per acre or higher. By late June or early July, the soybean yield expectations drop to 20-30 bushels per acre. The yield potential of late planted soybeans is highly variable, and is very dependent on favorable weather conditions in August and early September, as well as having a later-than-normal first frost date. It is best to consult with an agronomist or seed representative before finalizing crop replant decisions.

University research has shown that corn stands can be reduced up 50 percent with only a 20 percent reduction in yield potential, provided that the stand reductions are fairly uniform. Similarly, soybean stands can be reduced by up to one-third, with only a 10 percent or less loss of yield potential. It should be noted that there is a lot of variation in these results in actual field conditions due to gaps between plants in the row, and the health of the remaining plants in the field. Unfortunately, drown-out damage usually affects only a portion of the field, and that area is usually a total loss.

Another factor affecting replant decisions is Federal Crop Insurance policies, which allow producers some compensation for replanting following crop losses from heavy rains, hail or other natural causes. To qualify for replant compensation, farmers must have a loss area of at least 20 acres, or 20 percent of the total acres in an insured farm unit, whichever is less. The crop insurance replant provision can only be exercised once on the same crop acres. Some farm operators may have already used the replant option following poor emergence in May, and thus could not use the replant provision again in June, following the excessive rainfall.

A majority of farmers in the Upper Midwest insure their corn and soybeans with a Federal Crop Insurance policy using enterprise units, which group all acres of a given crop in a county together for calculating potential crop loss and insurance indemnity payments. By comparison, a crop insurance policy with optional units insures crops down to individual sections within a township. The reason more farmers choose enterprise units is to get higher insurance coverage levels at a lower premium cost. However, many times producers fare much better with optional units, as far as potential crop insurance indemnity payments, when dealing with more localized crop losses resulting from heavy rains or hail.  

Crop producers in the Upper Midwest who are facing either prevented planting or crop replant situations should contact their crop insurance agent for more details on the prevented planting and replant options with various crop insurance policies. The USDA Risk Management Agency (RMA) has some very good crop insurance information and fact sheets available online.

Nitrogen loss?

Another concern developing in some areas is the loss of available nitrogen for the 2018 corn crop, due to excessive rainfall and continual saturated soils. A large amount of the nitrogen fertilizer for the corn crop was applied last fall or early this spring, prior to corn planting. The very warm temperatures early this spring likely caused much of the soil nitrogen to convert to the nitrate form much earlier than when the nitrogen is needed by the corn crop. Once in the nitrate form, the soil nitrogen losses increase substantially during heavy rainfall events early in the growing season, such as has occurred in recent weeks. Some growers may need to consider supplemental nitrogen applications in order to maintain normal crop development.

Even though parts of southern Minnesota, northern Iowa, and southeast South Dakota have been dealing with delayed planting and excessive rainfall, which has slowed early season growth, many portions of the region have had very favorable growing conditions. As of mid-June, a large majority of the U.S. corn and soybean crop is rated in good-to-excellent condition. Long-range weather forecasts for late June across the Upper Midwest call for warmer temperatures, together with a bit drier weather pattern, which should greatly improve crop growing conditions in many of the areas that have been facing challenges in recent weeks. 

About the Author(s)

Kent Thiesse

Farm management analyst and vice president, MinnStar Bank

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