Greenhouse Gas Emissions as Influenced by Nitrogen Fertilization and Harvest Residue Management in Sugarcane Production

Abstract

Core Ideas Application of urea led to higher N2O emissions than urea–ammonium nitrate in sugarcane. Residue retention led to higher N2O and CH4 emissions irrespective of N source. Both N source and residue management did not affect CO2 emissions. Sugarcane (Saccharum spp.) is a major row‐crop in the southern United States with high rates of N‐fertilizer application and unique harvest‐residue management. A 2‐yr field experiment was conducted to investigate different N‐fertilizer effects (urea and urea ammonium nitrate, UAN) and harvest‐residue managements (residue‐retain, RR, and residue‐burn, RB) on greenhouse gas (GHG) emissions from soils under sugarcane production. In 2012, a split‐plot design experiment was conducted with residue managements as main‐plots and N‐sources as sub‐plots. In 2013, two experiments were conducted to investigate UAN effect under RR and RB, and N‐source effect under RB on GHG emissions. Nitrogen was applied at 135 and 157 kg ha‒1 in 2012 and 2013, respectively. Soil GHG emissions were monitored using a closed chamber method. Results showed the majority of N2O emissions occurred within 4 wk after N‐application. Average N2O emissions from urea‐treated plots were 1.43 to 1.67 times higher compared with UAN for 2 yr. Urea had a N2O emission factor of 3.52 and 4.45% under RB and RR, respectively, whereas UAN had 1.67 and 2.46% under the same residue management. Higher N2O emission under RR treatment was supported by 15 to 20% more water‐filled pore space (WFPS) in soil than RB plots, which also increased CH4 emissions. Higher correlation was found between N2O emission and WFPS in 2012 compared with 2013 (r2 = 0.52 vs. 0.36) because a majority of the rainfall in 2012 was received within 3 wk following N application. Nitrogen sources had no effect on CH4 and CO2 emissions.