Large Urea Granules for Broadcast Application for No-till Cropping - University of Alberta, Ellerslie, AB

It is generally accepted in the Canadian prairies that the use of so called “double-shoot” air-drill planting equipment capable of planting and 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 fertilizer. In order to speed up planting operations and allow more acres planted between fill stops, numerous farms are instead applying urea as a broadcast surface application prior to planting. The urea is broadcast on the soil using pneumatic fertilizer application trucks capable of speeds up to 25 mph making it is easy to quickly cover large areas of crop land in a day. These broadcast urea applications can be made either in the late fall or early spring. 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 urease and nitrification inhibitor additives available that can reduce over-winter losses of applied urea. Research in the 1980's also showed increased fertilizer use efficiency resulted from using large granule urea (0.5 in. diameter) compared to regular size urea (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, that were broadcast applied to no-till fields in the late fall, or the early spring, for spring planted barley. All the broadcast treatments were compared to the industry accepted standard of one-pass planting described above.

Generally the fall or spring broadcast applications resulted in crop yields similar to the side-banded one-pass planting treatment. During the four years of this study, there was little advantage observed to using the urease and nitrification inhibitors. There was little difference between the surface fertilizer applications using regular-sized urea compared to large granule urea. This does not mean that the urease and denitrification inhibitors did not work, however in the four years of measurements at this site, the weather conditions were not conducive for large ammonia volatilization or denitrification losses.