Growing conditions for corn and soybeans are quite variable across Minnesota. In south-central Minnesota most of the corn and soybeans were planted by mid-May and have emerged, with some of the early planted corn being 12-15 in. tall by the beginning of June. Overall the warmer and wetter conditions that existed in May across the state have been quite favorable for crop development; however, many locations have been impacted by excessive heavy rainfall events and severe storms during the month.
There are large areas of southwest, south-central and central Minnesota that lost portions of some fields due to excessive rainfall amounts during May, which has resulted in some replanting. There were reports of soybean emergence problems in portions of fields that were planted in mid-May, and then followed by intense rainfall events that caused some soil crusting following planting. Strong winds and blowing dirt on several occasions during May, as well as several hailstorms, also caused some crop damage in portions of the region.
Most farmers have discontinued replanting corn, except for severe crop-loss situations, due to the late planting date. In southern Minnesota, corn planted after June 5 has only about 50-60% of the expected yield potential, compared to corn planted in late April or early May. Soybean yield potential is also reduced with planting after June 1, but not as severely as corn, until very late June. 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% with only a 20% 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% 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 and the health of the remaining plants in the field.
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% of the total acres in an insured farm unit, whichever is less. The maximum replant compensation in Minnesota is $45.44/acre for corn and $37.65/acre for soybeans. The crop insurance replant provision can only be exercised once on the same crop acres, and some farm operators already used the replant option following heavy rains in early May, and thus could not use the replant provision again in late May, following another round of excessive rainfall. Producers should contact their crop insurance agent for more details on replant provisions.
Another concern that is developing as a result of the warm, wet spring, along with the excessive May rainfall amounts, is the loss of available nitrogen (N) for the 2012 corn crop. Much of the nitrogen fertilizer for the 2012 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 N 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 N losses increase substantially during heavy rainfall events early in the growing season, such as occurred in May this year. Many growers will likely need to consider supplemental N applications in order to maintain normal crop development. Producers should contact their agronomist or crop consultant for further considerations regarding additional nitrogen for the 2012 corn crop.
Editor’s note: Kent Thiesse is a former University of Minnesota Extension educator and now is Vice President of MinnStar Bank, Lake Crystal, MN. You can contact him at 507-726-2137 or via e-mail at firstname.lastname@example.org.