Watch Temperatures Before Making Nitrogen Applications

Apply to early and risk big N losses.

Published on: Sep 14, 2009

Once harvest gets underway, thoughts will run to tillage and perhaps fall fertilization. A practice many still like to get done in the fall is applying anhydrous ammonia to meet N needs for fields going to corn. But if you apply when soil temperatures are still too high, you may risk losing a sizable portion of the N, and still not have enough N around to meet the needs of the corn crop next summer.


One year ago Dave Nanda, a consultant, saw big N losses that resulted in lower yields where N was applied over the top, even in the spring, instead of sidedressed in the Corn Illustrated plots. However, the amount of rainfall that came after the N application and before sidedressing was extreme, about 20 inches. But he makes the point that N is very volatile, and can be lost if you don't treat it properly.


It can be more vulnerable in fall applications on wet soils. Nearly every agronomist today recommends applying it with N-serve if you're going to apply N in the fall. N-serve, around for some 30 years, is made by Dow AgroSciences, and helps keep N in forms for a longer period that are less likely to be lost than if no N-serve was applied with the fertilizer product.


New kid on the block from Dow AgroSciences is Instinct, also a nitrogen stabilizer. However, Chris Berry of Dow AgroSciences, explains it's for liquid UAN solutions and their application, or for manure applications. Its not meant to replace N-Serve in anhydrous ammonia applications. In fact, Instinct, just recently labeled and approved, uses the same active ingredient as N-Serve.


It's biggest impact is likely to be in the spring when broadcast liquid N solutions are sometimes vulnerable for loss. That's the market it's designed for, Berry says.


Meanwhile, most agronomists say don't apply N in the fall as anhydrous ammonia until soil temperatures are 50 degrees F or lower, and likely to stay there. Some say this should be at the four inch depth, others go so far as to say the six-inch depth.

Nearly all agree there are also parts of the country where N should not be fall applied. If you live in a location where the soil temperature is expected, based on historical data, to rise above 50 F at some point in every month of the year, then your best bet is to not fall apply anhydrous ammonia, no matter how tempting it might be in terms of relieving spring workload. The risk of N loss is just too great. This takes in portions of southern Ohio, southern Indiana and Illinois and points in the Corn Belt that lie along that latitude.