Nitrous oxide emissions in response to straw incorporation is regulated by historical fertilization

The incorporation of crop straw with fertilization is beneficial for soil carbon sequestration and cropland fertility improvement. Yet, relatively little is known about how fertilization regulates the emissions of the greenhouse gas nitrous oxide (N2O) in response to straw incorporation, particularly in soils subjected to long-term fertilization regimes. Herein, the arable soil subjected to a 31-year history of five inorganic or organic fertilizer regimes (unfertilized; chemical fertilizer application, NPK; 200% NPK application, 2 x NPK; manure application, M; NPK plus manure application, NPKM) was incubated with and without rice straw to evaluate how historical fertilization influences the impact of straw addition on N2O emissions. The results showed that compared to the unfertilized treatment, historical fertilization strongly increased N2O emissions by 0.48- to 34-fold, resulting from increased contents of hot water-extracted organic carbon (HWEOC), NO3-, and available phosphorus (Olsen-P). Straw addition had little impact on N2O emission from the unfertilized and NPK treatments, primarily due to Olsen-P limitation. In contrast, straw addition increased N2O emissions by 102-316% from the 2 x NPK, M, and NPKM treatments as compared to the corresponding straw-unamended treatments. These results indicated that N2O emissions in response to straw addition were largely regulated by historical fertilization. The N2O emissions were closely associated with the depletion of NO3- and decoupled from change in NH4+ content, suggesting that NO3- was the main substrate for N2O production upon straw addition. The stoichiometric ratios of HWEOC to mineral N and mineral N to Olsen-P were key factors affecting N2O emissions, underscoring the importance of resource stoichiometry in regulating N2O emissions. In conclusion, historical fertilization largely regulated the impacts of crop straw incorporation on N2O emissions via shifts in NO3- depletion and the stoichiometry of HWEOC, mineral N, and Olsen-P. (C) 2020 Elsevier Ltd. All rights reserved.