Long-term substitution of synthetic fertilizer by cattle manure: Effects on carbon footprint, carbon sequestration, and yield in a double rice system

The greenhouse gas (GHG) flux from rice crops under inorganic or organic fertilization has accumulated considerable interest due to ongoing agricultural intensification. However, impacts of substituting inorganic fertilizer with cattle manure or combining both on net greenhouse gas emissions (NGHGE), carbon footprint (CF), carbon sequestration, soil enzymes and sustainable grain yield in paddy soils are poorly understood. Treatments were CK (no fertilizers), NPK (synthetic fertilizers), M (full substitution of synthetic fertilizers by cattle manure), and NPKM (combined synthetic fertilizers with cattle manure). Results showed that M increased yield by 25.64 % in early rice and 27.24 % in late rice. The enzymatic activity like Acid phosphatase (AP), and β-1, 4-N-acetylglucosaminidase (NAG) increased in NPKM fertilization compared to M treatment. Carbon storage varied from 31.41 % to 62.38 % under M and NPKM. The contribution of NPK, M and NPKM fertilization for annual carbon sequestration rate was 20.62 %; 26.80 % and 40.21 % compared to CK, respectively. CH 4 emissions increased by 49.09 %, 13.61 %, and 8.96 % in early rice under MPKM, M, and NPK, respectively, while N 2 O emissions increased by 68.45 %, 31.90 %, and 19.83 % under the same treatments. For early rice, a strong positive association between NGHGE and methane (CH 4 ) emissions. In late rice, AK and soil pH were correlated negatively with GWP, rice yield, C, N, P cycling enzymes, N 2 O, and CH 4 emission, SYI, and CF. In summary, grain yield could promote while reducing carbon footprint by NPKM fertilizer with proper field management in rice season, where such cultivation is not yet practiced. Impacts on temporal greenhouse gas (GHG) emission characteristics, net GHG emissions, carbon footprint, and carbon sequestration under synthetic fertilizer substitution with cattle manure in a double rice system. NPK denotes synthetic fertilizers. NPKM represents combined synthetic fertilizers with cattle manure. GHGE is greenhouse gas emissions, and NGHGE denotes the net greenhouse gas balance. F-D indicates flooding until the ripening stage, followed by drainage. AWD indicates wetting and drying alternatively. CF represents the carbon footprint. The larger blue circles indicate a more sustainable yield index (SYI). CO 2 (carbon dioxide), CH 4 (methane), and N 2 O (nitrous oxide) emissions are presented. The white microbial structure represents colonies with mold bacteria. The size of the rectangles corresponds to the SYI, with larger rectangles indicating a higher SRI. The white circles with a “C” indicate carbon content. Bar graph showing C, N, and P-related enzyme activity under different fertilization regimes. AP; Acid phosphatase, BG; β-1,4-glucosidase, NAG; β-1,4-N-acetylglucosaminidase (NAG), LAP; L-leucine aminopeptidase (LAP). • NPKM fertilization reduced net GHG emissions in late rice seasons compared to early rice season. • For both rice season, M treatment increased C and P enzyme activities compared to other treatment. • M treatment reduced carbon footprint of area and yield scale (CF a and CF y ) in the double rice system. • NPKM fertilization increased the sustainable yield index (SYI) compared to other fertilization methods for both rice seasons. • Carbon storage and sequestration rates were higher under NPKM fertilization compared to other treatments.