Long-Term Organic and Inorganic Fertilization Effects on Greenhouse Gas Emissions and Soil Nutrient Stoichiometric Ratio in Rice-Rice-Fallow Cropping System

Abstract

Due to continual rice cultivation, greenhouse gases flux from paddy soil under organic and inorganic fertilization has received considerable attention. Long-term usage have a negative impact on greenhouse gas fluxes and soil nutrient stoichiometry, while assuring environmental safety remains uncertain. As a result, the study was done to estimate the effect and relationship among GHGs emission, net ecosystem carbon budget (NECB), soil nutrient stoichiometric ratio in rice-rice-fallow cropping system. There were five treatments chosen: CK (no fertilizer); NPK (inorganic nitrogen, phosphorus, potassium fertilizer); M (manure); PKM (inorganic PK fertilizer, manure); NPKM (inorganic NPK fertilizer, manure). Both PKM and NPKM fertilization raise soil C: N (carbon-nitrogen), C: P (carbon-phosphorus), N: P (nitrogen-phosphorus) ratios in soil compared to CK, while decreased N: K (nitrogen-potassium) ratio and boosting grain yield by 59–86%. The fallow season unrecompensed 9 to 13% of annual CH4 emission and then early rice elevated its proportion to 55% to 62%, whether late rice covered rest 38 to 45%. Compared to control, annual N2O emissions increased from (52-73) % to (103 to 115) % with PKM and NPKM fertilization in rice and fallow season. In case of early rice, C: P ratio and GHGI was negatively correlated with CH4 and N2O emission whether yield and CH4 have strong positive association with GWP. However, late rice season, GHGI was negatively correlated with CO2 and CH4 emission whether N2O have strong positive association with GWP. CO2 and N2O emission levels were greater in late rice rather than early rice in this experiment. However, CH4 emissions from early rice contributed more to annual GWPs, resulting in higher C equivalent emissions but a lower carbon efficiency ratio of rice output. The TOPSIS research suggested that PKM followed by NPKM was better than NPK and M fertilization in terms of yield and environmental sustainability.

Keywords: Greenhouse gases flux, Net ecosystem carbon budget, Carbon efficiency ratio, soil nutrient stoichiometry