The push for higher yields may mean you need to think about more than just lime, phosphorus and potassium when you design your fertilization program for corn. Barry Fisher, a conservation farming specialist with the Natural Resources Conservation Service in Indiana, says it's time that no matter what tillage system you're in, you ought to think about micronutrients when you think about corn nutrition.
Zinc, boron, manganese and sulfur are just some of the micronutrients that some are adding today in their quest for higher yields. Sulfur has only recently made the list. For many years in the central Corn Belt, enough utility plants burned coal with sulfur emissions to satisfy the needs of the crop. However, now that plants have been required to add scrubbers to remove sulfur when coal burns, sulfur levels have declines significantly in many areas.
Some people rely on soil tests for deciding whether to use such micronutrients as zinc or boron. However, historically, these tests have not been as accurate for micronutrients as for the major nutrients, including phosphorus and potassium. Fisher says there's another way to monitor micronutrient nutrition that might make sense in many operations.
"One way to do it is by pulling tissue samples in the summer while corn is growing," he says. "These tissue samples seem to be reliable for many of these nutrients in this category."
If you're going to take tissue samples, you may want to work with a spoils consultant, or someone who has experience in pulling and preparing tissue samples. As with soil testing, it's garbage in, garbage out. The testing will only be valuable if it is done correctly. Most labs that process soil samples can also do tissue samples during the growing season.
Taking tissue samples to see what nutrients are present, or which might be deficient, is preferable to adding in a mix of micronutrients that you might not need. The only way to know if you need micronutrients is to monitor their uptake and usage in the [plant. That is what tissue sampling is designed to help you figure pout.