As we move toward fall fertilization season and planning for spring 2012, the question of nitrogen (N) stabilizers comes up. Can we apply a material with our N fertilizer to protect it from loss? SDSU Extension Soils Specialist Ron Gelderman and SDSU Extension Field Specialist Mark Rosenberg offer some tips.
Timing and placement is key when applying additives
Nitrogen in the form of urea can be lost through ammonia volatilization when surface applied. Eventually all forms of nitrogen will convert to nitrate and are subject to leaching or denitrification losses. For growers to obtain a bigger bang for their applied N buck, different N materials and N additives may be used, but timing and placement is the key.
Nitrogen materials applied in the fall should be delayed until after soil temperatures are below 50° F. As of Oct. 16, soil temperatures at the 4-in. depth were still ranging from 51° to 57°. In addition, N should be either incorporated with tillage or, with no-till, it should be injected into the soil. If this is not possible or practical, N applications should be delayed until late winter or early spring, and there is no snow cover. At these times conditions are usually cool and moist and do not favor ammonia volatilization.
If surface N applications need to be made later in the spring, a urease inhibitor should be considered with the application. For coarse textured soils in eastern South Dakota and medium textured soils in southeastern South Dakota, which have a profile full of water, growers should consider use of a nitrification inhibitor with spring N applications.
Effective urease and nitrification inhibitors are discussed in a new publication "Nitrogen Extenders and Additives for field crops" and can be found online.