Do you feel that? It’s the squeeze of too much to do with too little time. As the calendar days tick away, many farmers are moving at lightning speed to apply fertilizer, kill weeds and get seeds in the ground—but can you cut out one of those steps? You might be able to apply fertilizer after planting with no yield drag—but you need to plan ahead to have the fertilizer and equipment you need. John Sawyer with the Department of Agronomy at Iowa State University shares the best options for sidedressing nitrogen, in order from most to least preferable:
Injected anhydrous ammonia, UAN or urea
Broadcast dry ammonium nitrate, ammonium sulfate or urease treated urea
Surface dribbled UAN solution between rows
First, know the difference between anhydrous ammonia and urea and what inherent risks or advantages each provides.
“[Anhydrous ammonia] can be a fickle form of nitrogen as product can easily be lost if, when knifed in, the soil is damp and clumpy or very sandy as the knife openings might not fully close which allows anhydrous ammonia to escape into the air,” says Davis Michaelsen, editor of Pro Farmer Inputs Monitor. In addition, there are human and environmental safety concerns with this form of nitrogen. All said, anhydrous is still the most popular form of nitrogen for many farmers as it’s quickly available for plants. For those considering alternative forms, due to anhydrous shortages or its cost, urea is another widely used, effective nitrogen source. “Urea is available in granular, prilled or liquid form,” Michaelsen explains. “In its granular form, urea can be surface applied, but must be incorporated to avoid nitrogen lose. Losses of up to 50% have been observed when dry urea has been spread over moist ground.” If you decide to inject nitrogen, in any form, wait until you know where the rows are—either just after emergence or with GPS equipment, Sawyer says. This avoids “burning” the plants with nitrogen applications “It’s easiest to inject the row middle and there is no advantage in attempting to place the band close to the row,” he adds. “Corn roots will reach the row middle at a small growth stage. Injected nitrogen can also be applied between every other row—it provides an equivalent response as when placed between every row.” It’s also important to note you might see plant responses from broadcasting urea or ammonium sulfate. “It might cause some leaf spotting or edge browning where fertilizer granules fall into the corn whorl,” Sawyer says. “The chances of this happening increases with larger corn. As long as the fertilizer distribution is good and not concentrated over plants, the leaf damage should only be cosmetic.”