Lime Application Reduces Methane Emissions Induced by Pig Manure Substitution from a Double-Cropped Rice Field

The substitution of chemical fertilizers with organic manure plays a critical role in sustainable crop production. Nevertheless, organic amendments promote the global warming potential (GWP) in rice paddies due to increased methane (CH 4 ) emissions. Increasing evidence shows that lime application can reduce CH 4 emissions from acidic paddy soils; however, it is still not clear whether liming can reduce the GWP in rice fields under organic manure substitution. A two-year field experiment was conducted to investigate the impacts of pig manure substitution and lime application on grain yield, CH 4 and nitrous oxide (N 2 O) emissions in a subtropical double-cropped rice field in China. The experiment consisted of three treatments: CF (100% chemical nitrogen fertilizer), 1/2N + M (50% of the applied nitrogen substituted by pig manure, M represents manure), and 1/2N + M + L (lime amendment with 50% of the applied nitrogen substituted with pig manure, L represents lime). On average, 1/2N + M reduced rice yield by 5.65% compared to CF, while the lime application had no effect on rice yield. Mean cumulative CH 4 emissions were 218.8% higher in 1/2N + M than in CF, whereas 1/2N + M + L reduced CH 4 emissions by 36.6% compared to 1/2N + M. Neither pig manure substitution nor lime application affected N 2 O emissions. Consequently, 1/2N + M increased the GWP and greenhouse gas intensity (GHGI) by 214.6% and 228.3%, respectively, compared to CF. In contrast, 1/2N + M + L reduced the GWP and GHGI by 36.4% and 36.5% compared to 1/2N + M. Lime application can mitigate CH 4 emissions and GWP induced by pig manure amendment in double-cropped rice fields.