Modifying nitrogen fertilizer practices can reduce greenhouse gas emissions from a Chinese double rice cropping system

Practical nitrogen fertilizers are required that simultaneously increase yield and reduce greenhouse gas (GHG) emissions from rice (Oryza sativa L.) paddies. A field experiment was conducted to measure methane (CH4) and nitrous oxide (N2O) fluxes in situ during two double rice-winter fallow rotations (2012-2014) under five different nitrogen fertilizer treatments: traditional urea (CM), polymer-coated controlled release urea (CRU), urea with N-Sever nitrapyrin (NU), urea with 3,4-dimethylpyrazole phosphate (DMPP), and urea with effective microorganisms (EM). The results revealed that GHG emissions ranged between 77.2 and 178.2 kg CH4 ha(-1) and 4.18 and 10.11 kg N2O ha(-1) averagely over the whole rotation, and significant differences (P < 0.05) among treatments and seasons were found. N2O emissions accounted for 26.6-36.9% of total GWP, and significant N2O emissions were observed during the winter fallow period, ranging from 3.1 to 3.88 kg N2O ha(-1). Compared to the GWP (7.66 and 8.85 Mg CO2 ha(-1)) and GHGI (0.52 and 0.63 Mg CO2 Mg-1 grain) from CM in 2012 and 2013 rotation, respectively, CRU achieved the highest reduction (48.5% for GWP and 55.4% for GHGI) in 2012, NU achieved the highest reduction (37.6% for GWP and 43.1% for GHGI) in 2013, and other treatments also realized different levels of decrease. Thus, controlled release urea, nitrification inhibitor or effective microorganisms might be effective fertilization options for low-carbon rice production with high yield. (C) 2015 Published by Elsevier B.V.