Nitrogen fertilizer in combination with an ameliorant mitigated yield-scaled greenhouse gas emissions from a coastal saline rice field in southeastern China

Coastal saline rice fields play an increasingly important role in rice production and associated greenhouse gas (GHG) emissions. However, few studies investigated the influences of nitrogen (N) fertilizer and soil ameliorant on GHG emissions simultaneously in this region. Thus, a field experiment was established to study the effects of different N fertilizers and soil ameliorant on global warming potential (GWP) and yield-scaled GHG intensity (GHGI) after accounting for carbon dioxide (CO2) equivalent emissions of methane (CH4) and nitrous oxide (N2O), agrochemical inputs, and farm operations along with agronomic nitrogen use efficiency (NUE) during the rice season of 2016 in a coastal saline paddy in Lianyungang, China. The experiment was initiated with four N treatments (N0, no N; Nu, urea; Nm, organic-inorganic mixed fertilizer; Nw, organic fertilizer made from wheat straw) and two ameliorant (A) treatments (A0, no ameliorant; A1, 22.5 kg ha−1 ameliorant). The results showed that three N fertilizers significantly increased the CH4 emissions, N2O emissions, GWP, and grain yield by 42.2% (p < 0.001), 57.1% (p < 0.001), 49.8% (p < 0.001), and 58.9% (p < 0.001), respectively. NuA1, NmA1, and NwA1 treatments obviously reduced the yield-scaled GHGI by 21.3%, 16.3%, and 12.4%, respectively, relative to the corresponding NuA0, NmA0, and NwA0 treatments. Overall, although three N fertilizers would increase the GWP, combining an ameliorant amendment with N fertilizer can effectively reduce the yield-scaled GHGI and meanwhile increase the grain yield, particularly the NmA1 strategy.