Large Urea Granules for Broadcast Application for No-till Cropping in Alberta Spring Wheat

It is generally accepted in the Canadian prairies that the use of so called “double-shoot” air-drill planting equipment capable of planting and side-banding fertilizer in one field operation is the most effective way to apply N fertilizer. Granular urea is the most widely used N fertilizer in this type of operation. The urea is sideband placed (1.5 in. to the side and 1.5 in. deeper) than the bottom of the seed furrow. However, handling all the urea at planting requires numerous stops to fill the separate air-drill tanks with urea, seed grain and starter P fertilizer. To speed up planting operations, numerous farms are now applying urea as a broadcast surface application prior to planting. Usually the spring timing of broadcast applications results in greater crop yields, and higher fertilizer use efficiency compared to fall applications due to less opportunity for denitrification or leaching losses of applied N. There are nitrification inhibitor additives available that can reduce over-winter losses of applied urea, and a urease inhibitor to reduce ammonia volatilization losses of surface-applied urea. Research in the 1980's demonstrated the potential for increased fertilizer use efficiency from large granule urea (0.5 in. diameter) compared to regular-sized urea granules (0.125 in. diameter). This research study was conducted to compare crop yields from regular and large-sized urea, with and without urease and denitrification inhibitors, broadcast onto no-till fields in the late fall, or the early spring, for spring wheat (one site near Acadia Valley, Alberta), or winter wheat (planted at two sites one near Acadia Valley and the other near Stavely, Alberta). All the broadcast treatments were compared to the commonly accepted standard of one-pass planting/fertilizing described above for wheat.

The fall or spring broadcast urea applications resulted in crop yields similar to the side-banded one-pass planting treatment. During the three years of this study, there was little yield advantage to using the urease and nitrification inhibitors. Also, there was little difference in yield between the surface applications using regular urea, compared to large-granule urea. This does not mean that the urease and denitrification inhibitors did not work, but while conducting this study, the weather conditions were not conducive for large ammonia volatilization or denitrification losses.