Banded urea placement did not affect nitrous oxide emission from furrow-irrigated Vertisols

Episodic nitrous oxide (N2O) emissions from Vertisols used for furrow-irrigated cotton production mainly occur in response to early season irrigation events. This study evaluated the impact of N fertiliser placement and timing strategies on N2O emissions from Vertisols under cotton production in northeast Australia. We compared N2O emissions in two experiments during the 2015-16 summer. Each experiment consisted of two site-years of data from different commercial cotton paddocks. Experimental comparisons were: (1) all N fertiliser applied pre-plant vs split-N application and (2) applying pre-plant N fertiliser into the irrigated vs non-irrigated side of the plant bed. Where all N fertiliser was applied pre-plant, 46-96% of total N2O emissions occurred in response to the first irrigation. Where N application was split, 33-34% of total N2O emissions followed the in-crop N applications, 2-7 times more than from the same irrigations where no in-crop N was applied (all pre-plant). Splitting N application between pre-sowing and in-season applications gave no difference in cumulative N2O at one site but increased total N2O loss at the other (99 vs 63 g N2O-N/ha). Changing the placement of the pre-sowing N fertiliser band from the non-irrigated to the irrigated side of the hill changed the source location of N2O emissions but the not the cumulative N2O loss. Varying the timing and placement of pre-plant N application affected the spatial and temporal intensity of soil N2O emissions, but generally not the overall total loss of N2O.

Automated summary

This study evaluated the impact of different nitrogen fertilizer application methods and timings on N2O emissions from Vertisols in northeast Australia. The results showed that split-N application significantly reduced total N2O emissions.