Turf Response to Reduced Rates of Polymer Coated Urea.

Although N is beneficial and essential for life, it is also a common atmospheric pollutant as nitrous oxide (N₂O) and ammonia (NH₃)—contributed largely from N fertilization. Turfgrass is the irrigated and fertilized crop with greatest acreage in the USA. Fall and spring applied N fertilizer trials were conducted over two years in an effort to determine if various slow and controlled release N fertilizers were equivalent to traditional urea and to determine if a reduced rate of controlled release N could be used for improved N use efficiency. An unfertilized control was compared to sulfur coated urea (SCU), polymer and sulfur coated urea (XCU), polymer coated urea (Duration 75 or 125; DR) at 50, 75, and 100% (full) rate, and urea either applied at all once or split monthly. Urea, SCU, and XCU resulted in significantly increased biomass growth and verdure shortly after application, but diminished with time showing that the release of N was not spread evenly over the course of each study. The DR applications did not immediately increase growth and verdure in the spring applied study, but eventually evened out with the other fertilizer materials--resulting in reduced mowing requirement at the expense of verdure initially. The fall applied DR performed equivalent to the other fertilizers in the fall applied N study in terms of verdure, but resulted in less overall biomass growth (reduced mowing requirement). The DR is effectively applied as a controlled release fertilizer at reduced rate (50%), although it likely needs to be mixed with urea or another product that provides a short term release of N. Previous results show that DR has less gaseous N loss to the atmosphere, which explains the improved N use efficiency observed in this study.