Broadcast N – How to do it better

Surface spreading of nitrogen (N) fertilizer in the fall can lead to major N losses. Broadcast N should be incorporated and/or include urease and nitrification inhibitors to reduce those losses. 

The better option for fall is banding into the soil – preferably as late as possible but not so late that the soil is too cold to reseal around the band. Banding helps to slow down the conversion of N fertilizers such as urea (46-0-0) or anhydrous ammonia (82-0-0) into nitrate, which is vulnerable to leaching and denitrification. Furthermore, banding also helps to reduce volatilization and the amount of N immobilized by soil microbes. 

Before banding, consider soil moisture. Banding in wet soil conditions will increase ruts, and wet soils can also increase losses if the soil does not close well over the band. Banding in dry soils can also increase gassing-off losses because soil does not provide a proper seal on the band. 

Another option is anhydrous ammonia (NH3), but this has the potential for significant volatilization losses if shallow application is made in dry, sandy or lumpy soils. If the surface soil is very dry and sandy, place the ammonia deeper (4” or so) to moisture to aid in retention and conversion to ammonium. The greater depth also gives the ammonia gas more opportunity to react with water and the soil before it diffuses through the pores to the surface. Also make sure the injection channel is sealed. If the soil is very lumpy with large pores, this will reduce contact and increase rate of movement of ammonia gas to the surface. Under these conditions, a granular or liquid form of N may be a better selection, but even with these forms it is important that the fertilizer is covered with soil. In general, the best management practice for NH3 is deep injection under moist conditions with good slot closure, and ideally into cool soil temperatures – below 10°C, but not frozen.