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

Abstract

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 178.2kg CH4ha−1 and 4.18 and 10.11kg N2Oha−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 3.88kg N2Oha−1. Compared to the GWP (7.66 and 8.85MgCO2ha−1) and GHGI (0.52 and 0.63MgCO2Mg−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.