July 6, 2015 By Dave Nanda, Director of Genetics and Technology for Seed Consultants, Inc.
June 2015 has been a very wet month in most of the Corn Belt setting new records in many places. Some of the corn fields I have visited recently are showing N-deficiency symptoms. Nitrogen is one of the most important elements needed by all green plants for chlorophyll production and for photosynthesis. Urgent action is needed in some fields to save this crop.
• If lower leaves of your corn crop are getting yellowish, starting in mid-rib and moving towards edges, there is a good chance it is a sign of N-deficiency.
• Should you apply additional nitrogen? It depends on how, when and how much nitrogen you have already applied? Did you apply it in the fall and use a nitrogen stabilizer? What form of nitrogen did you use? Do you generally sidedress?
• Some people have suggested soil testing before sidedressing. Well, that may be OK if you had plenty of time, but in my opinion, these tests during the growing season are not reliable, especially with lot of rains we have experienced in June this year.
• Even tissue tests and optical sensors developed so far are not dependable in predicting the needs of corn plant. You are trying to rescue your crop and based on your soil type, planting date and yield potential, you should apply adequate amount of nitrogen when signs of N-deficiency are apparent.
• You need to have a total of 0.8 to 0.9 pound of N per bushel of expected yield. Corn plants need nitrogen now, before tassel emergence when it is growing fast. So don’t waste a lot of time doing testing at this time and apply a realistic amount of N as soon as possible.
• You can also use foliar applications of nitrogen to supplement the amount you need later, if necessary, but make sure your crop is not suffering from lack of this essential nutrient if you want to harvest a good crop!