Managing corn to produce a net return is always difficult. When corn prices are below breakeven and tariff threats loom, it is downright troublesome. Can you afford to invest more in this crop? Or should the question be: When can you afford not to invest to produce enough bushels to increase gross income?
Dan Quinn, Purdue Extension corn specialist, and Mark Licht, Iowa State University Extension cropping systems specialist, share their opinions on how to handle tough situations regarding corn and nitrogen this year. Here are two real-world scenarios these agronomists encountered:
Scenario 1
We applied 180 pounds of N preplant on a tiled field. Spring rains were heavy. Corn is at V10 to V12, with firing already on lower leaves. What can we do?
Quinn: You can still apply nitrogen. The crop will still respond to additional N. Applications at V10 often do not provide additional benefits beyond earlier-season sidedress applications unless N loss conditions occur, and a rescue N application is required. However, the recommended way to apply N here would be with a high-clearance sprayer. Band N between rows or next to them.
I advise against a topdress application of dry N fertilizer. Applying 20% to 25% of the total recommended N now is typically adequate to help limit yield losses.
Licht: Leaf firing on lower leaves is an indicator of N deficiency. Don’t confuse this with natural leaf senesce of lower leaves as light penetration decreases to those leaves. If you see N deficiency, you have already lost some yield. Factor it into determining how much benefit you may get from a rescue N application.
Consider how fast a rescue application can be made. Newer corn hybrids take up N through pollination and even a little during blister stage. Come in with high-clearance equipment, with drop nozzles or Y-drops, to get UAN to roots faster without burning or damaging leaf tissue.
Scenario 2
We applied 120 pounds of N preplant. The stand is good. We were going to add 40 to 60 pounds of N at V12 as a planned midseason application. Cost of the application pass without fertilizer is $12 per acre. Should we do it? And if so, 40 or 60 pounds?
Quinn: In most cases, 120 pounds per acre isn’t adequate to achieve necessary yields and prevent N deficiencies later. Apply additional N because there is a high chance that even with the additional $12-per-acre application cost, it will be profitable. To figure total N to apply with this midseason application, use an N fertilizer recommendation tool, such as Purdue’s.
Match the required total N for your area with fertilizer price and corn price. This will give you a good estimate of the total N required for your area and the total amount of N to include in the midseason application.
Licht: High-yielding corn almost always requires more than 120 pounds of nitrogen per acre. Spring weather will drive additional N needs. A wet spring where N movement and losses are greater will lead to needing another 60 pounds per acre. Average spring precipitation may only require an additional 10 to 20 pounds of N per acre. As long as yield potential remains high, 120 pounds of N will not achieve target yield potential.