Although we are a bit of ways out from fall anhydrous application time, it will soon be here before we know it. Fall application can reduce soil compaction, but it also presents a great probability of nitrogen loss. Extension agronomist Angie Rieck-Hintz gave insight as to fall anhydrous do’s and don’ts for this season in an Iowa State University Extension article.

In order for organic nitrogen to mineralize, soil moisture is needed. This will allow the organic nitrogen to change to ammonium, while later becoming nitrate. Nitrate is the portion of nitrogen that is available for uptake, but it is also more susceptible to leeching and denitrification losses. “Applied anhydrous ammonia needs to change into ammonium by soil moisture so it can be available for uptake and held on the soil clay particles and organic matter as ammonium. If this process does not happen or happens slowly due to lack of soil moisture, much of the ammonia can be lost at injection because of limited knife track closure,” warned Rieck-Hintz.

Beware of applicating when soil conditions are questionable. If application causes cloddiness, air pockets, or fails to cover the knife track, it may be worth holding out and waiting for better conditions. Application under wet conditions can cause the knife track to smear and some ammonia to volatize because of inadequate knife track closure. “Don’t make a shallow application with the idea that any rain we do get will prevent volatilization. Keep application depth at your normal placement depth,” said the extension agronomist.

Apply anhydrous ammonia when soil moisture is 5 to 6 inches down to avert ammonia volatilization losses. Wait until soil temperatures average at least 50°F or before freezing to apply. “If soil moisture conditions are questionable, make a pass around the field. If you can smell ammonia, make adjustments to equipment or wait until conditions are more suitable,” said Rieck-Hintz.

Fall anhydrous application gives farmers the opportunity to spread out the workload, but it also comes with the risk of a greater loss of nitrogen. Farmers may want to consider a split application, applying some anhydrous in the fall and some in the spring. This presents a smaller amount of risk, but it still provides a head start once spring rolls around. Do what’s best for your farm’s workload capabilities and bottom line when it comes to fall anhydrous application.