Nitrogen supply and greenhouse gas emissions from a Black Vertosol amended with urea and ENTEC® urea

Constance M.Coverdale1, Alice R. Melland2, Diogenes L.Antille2

1 University of Southern Queensland, Toowoomba, QLD, 4350, Australia, [email protected]

2 University of Southern Queensland, National Centre for Engineering in Agriculture, Toowoomba, QLD, 4350, Australia

Abstract

The Australian cotton industry currently has an average nitrogen (N) use efficiency of 25% and is aiming to improve this to 40%. Improving the timing and rate of soil and fertiliser N supply can help meet this target. This research compared the soil and fertiliser mineral N supply after application of urea and ENTEC® urea (which contains a nitrification inhibitor). Greenhouse gas emissions of nitrous oxide, methane and carbon dioxide were also compared. Data were collected by conducting a 60 day aerobic incubation of pots of a Black Vertosol soil under a constant air temperature (25oC) and soil moisture range (>75% field capacity). The two N fertilisers were applied at 600 kg/ha N and were compared with an unfertilised control. Soil nitrate and ammonium concentrations and greenhouse gas fluxes were measured on up to nine occasions throughout the incubation. Mineral N supply from ENTEC® urea continuously increased over 60 days whereas the mineral N supply from urea peaked by day 14. The ENTEC® urea treatment also yielded 73% lower nitrous oxide emissions than the urea treatment. In the field, if N fertiliser was applied at cotton planting, the N supply from ENTEC® urea may better coincide with peak plant demands than urea.