Effect of nitrogen inhibitors on nitrous oxide emissions and pasture growth following an autumn application in a volcanic soil.

Erika Vistoso1*, Marta Alfaro1, Surinder Saggar2, Francisco Salazar1

A range of technologies is available to reduce greenhouse gas emissions from agricultural systems. Among these, applyingN transformation inhibitors is promising in reducing nitrous oxide (N2O) emissions in both arable and pastoral soils.A completely randomized block design with six replicates was used to quantify the effect of urease (UI) and nitrification (NI) inhibitors on N2O emissions and pasture production from permanent pasture in an Andisolafter autumn-applied urea. The N2O emissions were measured periodically for 8 wkwithPVC stationary chambers. Mineral N, DM yield, N concentration, and N uptake were analyzed. Our results show that adding fertilizer (40 kg N ha-1) significantly increased N2O emissions by 281% over the control treatment (P <0.05) and adding N inhibitors to fertilizer N resulted in a 10%-29% reduction in emissions. Both inhibitors initially reduced nitrate-N production in the Andisol (Osorno series) either by slowing urea hydrolysis or the nitrification process. Increases in pasture yield (8%-13%), N concentration (7%-9%), and N uptake (46%-56%) were measured by addingN inhibitors with urea. Emission factors, measured under field conditions in Chile after autumn- applied urea and N inhibitors (applied alone or combined), were very low (0.052%-0.114%) compared with values reported in the literature and the Intergovernmental Panel on Climate Change(IPCC)default value (1%). Using these technologies could contribute to Chile’s nationally established goal of a 20% reduction in greenhouse gas emissions by 2020.

Keywords: Andisol, emission factor, urease inhibitor, nitrification inhibitor, urea.
1Instituto de Investigaciones Agropecuarias INIA, Casilla 24-O, Osorno, Chile. *Corresponding author (evistoso@inia.cl).
2Landcare Research, Private Bag 11052, Manawatu Mail Centre, Palmerston North 4442, New Zealand.