An Iowa State Agronomy professor urges farmers to wait until November until applying anhydrous ammonia to their fields.
As many farmers begin to wrap up harvest, they might already be thinking about fall fertilizer application.
Iowa State Agronomy Professor John Sawyer says you need to wait until soil temperatures are 50 degrees or cooler.
“What we’re trying to do is to keep the applied nitrogen in the ammonium form. Nitrification is the process of converting ammonium to nitrate as a biological conversion and that happens more rapidly with warmer temperatures. If the soil is cold, the conversion is slow and the ammonium will stay as ammonium longer,” Sawyer said.
Sawyer says application works the best when the soil is moist.
“We like to have moisture there for the ammonia to be absorbed into the water. That helps limit the movement of ammonia at application. The flip side of that is if it is really wet we’ll get smearing as the knife goes through the soil and we have ammonia coming back up the knife track so we like to have good soil conditions. We have untreated soil crumbling back over that knife track to trap any ammonia that tries to get to the soil surface,” Sawyer said.
He again says to be conscious of applying anhydrous until cooler weather and also says pay attention if soil conditions are not right. Sawyer says other factors are just as important as moisture content. They also include depth of injection and soil coverage, especially with dry soil or coarse textured soil. He says anhydrous ammonia has been successfully injected into sandy soils at rates over 200 lb N/acre. Sawyer adds there is no real limit or maximum application rate when applying anhydrous ammonia into the soil.