Considerations for In-Season Nitrogen Applications
Nitrogen is a backbone of corn production. It is crucial for amino acids, chlorophyll, protein and therefore, yield. Careful management is needed as we head into a season of possible record input cost. If in-season application of nitrogen is in your plan, there are three main goals: 1) apply at the right time, 2) apply at the right rate, and 3) use a trusted nitrogen stabilizer on urea based products. Aiming for these goals will help reduce volatilization and maximize the N that is available to the crop.
Apply at the right time
It is key to put nitrogen products on before the crop needs the nutrient. Corn begins a large uptake of N between V8 to V14 as it starts to set the number of potential kernels and quickly adds plant height. To stay ahead of that, many universities and studies suggest that the optimal window for most in-season applications is between V4 to V6. If weather conditions get in the way, shoot for earlier rather than later. We never want the crop to think it is hungry for N! In a perfect world where weather conditions didn’t work against us, we would like to have 0.25-0.5 inches of rainfall within two days of application. If that rainfall isn’t on the horizon, add a nitrogen stabilizer to your application.
Add a stabilizer
Nitrogen stabilizers can come in different forms but the important group for in-season application is products containing urease inhibitors. Urease inhibitors help protect urea fertilizers from a process called volatilization. This is when nitrogen is lost to the atmosphere in the form of ammonia gas. This can be a leading cause of loss to in-season fertilizers as they are more likely to sit on top of the soil surface. N loss through volatilization is hard to quantify but is more likely to happen in fields with high N rates, insufficient rainfall, high temperatures, high amounts of crop residue, wet soil, and high soil pH. The addition of urease inhibitors can’t stop volatilization completely but can significantly slow the process and give more time before a rain or incorporation.
Apply at the right rate
When choosing to apply, the right rate is key to profitability. At the time of this writing, the local UAN price is $670/ton for 32%. That math works out to $1.05/unit N. It is an amazingly high price given historical values. It is important to apply a rate that is as close to what that crop actually needs. Take into consideration historical yield of the field, current yield potential and anything that may be limiting the field. Extra N will not save a crop that has been severely limited by issues such as drought or poor planting conditions. Use nitrogen rate calculators such as the CORN NITROGEN RATE CALCULATOR at http://cnrc.agron.iastate.edu/ to help understand the economics of different rates.