Creeping bentgrass and bermudagrass golf course greens are capable of absorbing urea through the leaf (foliage). Arkansas researchers found most of the nitrogen in the form of urea is absorbed within 4 hours with the greatest increase within the first hour. However the efficiency in which the nitrogen was absorbed was inconsistent varying from 32 to 69 percent for both creeping bentgrass and bermudagrass. There were no consistent seasonal trends that could account for the wide range. In addition, the researchers found that as you increased the rate of nitrogen efficiency decreased.
For maximizing nitrogen foliar efficiency uptake by the plant using urea recommendations would include i) the application rate should be low (<0.5 g N m-2) and ii) wait several hours to maximize foliar uptake before applying water (irrigation). Then apply water to wash any unabsorbed urea remaining on the leaf surface into the soil may provide for a second chance uptake by the root system.
Stiegler, C.J., M.D. Richardson, and D.E. Karcher. 2011. Foliar nitrogen uptake following urea application to putting green Turfgrass Species. Crop Science 51: 1253-1260.