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

•Polymer coating urea halved the GWP and improved crop yields.•Polymer-coated urea reduced CH4 emission significantly.•Nitrification inhibitors reduced N2O emission significantly.•N2O emissions accounted for 27–37% of total GWP over whole rotation.•N2O emissions and CH4 consumptions were notable during fallow period.

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 (CK), 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 CK 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.