Effect of polymer-coated urea on nitrous oxide emission in zero-till and conventionally tilled silage corn

Abstract

Little is known about nitrous oxide (N2O) emission from silage corn (Zea mays L.). Studies have shown that controlled-release N fertilizers have the potential to reduce N2O emissions, compared with conventional N fertilizers. This 2-year field study compared N2O emissions from urea fertilizer and a slow-release polymer-coated urea (CRU) applied to silage corn on soils managed with conventional tillage (CT) and zero tillage (ZT). The study was conducted on a silty loam soil in the cool, moist climate of south coastal British Columbia, Canada, taking year-around measurements from static chambers. Over 2 study years there was a significant interaction between N sources and tillage methods; under CT there was no significant difference between CRU and urea (557 vs. 447 g N2O-N ha-1 year-1, respectively), but under ZT, emissions from CRU were significantly higher than from urea (968 vs. 381 g N2O-N ha-1 year-1, respectively). Annual emissions of N2O-N ranged from 0.09 to 0.65% of applied N fertilizer. The CRU also had significantly greater emissions than urea per unit N uptake and plant yield under ZT, while there was no significant difference between N sources under CT. The results do not indicate that NO3- release from broadcast CRU matches corn growth or reduces emission of N2O.