Temperature Sensitivity of Soil Organic Carbon Mineralization under Contrasting Long-Term Fertilization Regimes on Loess Soils

To evaluate the temperature sensitivity of soil organic carbon decomposition (Q 10 ) following long-term contrasting fertilization regimes on loess soils and analyze its relationships with environmental factors. Long-term experiments involved three fertilization regimes, i.e., control (no nutrient input, CK), chemical fertilizers (CF), and organic manure plus chemical fertilizers (MCF), which were applied to investigate Q 10 by incubation experiment at different temperatures for a rain-fed cropping system in the Loess Plateau. Compared with CK, applications of CF and MCF significantly increased soil organic carbon (SOC) contents by 12% and 78% across sites. The Q 10 values ranged from 1.64 to 2.69, 1.97 to 2.93, and 2.09 to 3.12 for CK, CF, and MCF, respectively, across all sites, and the Q 10 values at 15-25°C were higher than those at 25-35°C. Applications of CF and MCF yielded the similar Q 10 values that were markedly greater than the values from the CK by 24% and 29%, on average. In addition, the mean Q 10 values of labile organic carbon and stable organic carbon were 1.28 and 3.65 across treatments and sites. Long-term applications of CF and MCF also markedly increased Q 10 of labile organic carbon by 10% and 39%, and of stable organic carbon by 34% and 34%, respectively, relative to CK. The variation of Q 10 was closely related to clay content, SOC and its pool sizes, and climate conditions. Long-term application of MCF significantly enhanced SOC relative to the CF, but with the similar Q 10 values for these two fertilization regimes. These results suggest that continuous application of MCF has great potential for less proportional SOC decomposition than the CF under global warming. Thus, the MCF is recommended as the nutrient management practice on loess soils.