Soil CO2 emissions from a cultivated Mollisol: Effects of organic amendments, soil temperature, and moisture

A field experiment was conducted to examine the influences of long-term applications of maize straw and organic manure on carbon dioxide (CO2) emissions from a cultivated Mollisol in northeast China and to evaluate the responses of soil CO2 fluxes to temperature and moisture. Soil CO2 flux was measured using closed chamber and gas chromatograph techniques. Our results indicated that the application of organic amendments combined with fertilizer nitrogen, phosphorus and potassium (NPK) accelerated soil CO2 emissions during the maize growing season, whereas NPK fertilization alone did not impact cumulative CO2 emissions. Cumulative CO2 emissions were higher from soils amended with pig manure relative to those with maize residue. Cumulative CO2 emissions during the growing season were 988 and 1130 g CO2 m−2 under applications of 7500 and 22,500 kg ha−1 pig manure combined with NPK, respectively, which were 42 and 63% higher than the emissions from the control (694 g CO2 m−2). The applications of 2250 and 4500 kg ha−1 maize straw combined with NPK marginally increased soil CO2 emissions by 23 and 28% compared with the control, respectively. A log-transformed multiple regression model including both soil temperature and moisture explained 50–88% of the seasonal variation in soil CO2 fluxes. Cumulative soil CO2 emissions were affected more by applied treatments than by soil temperature and moisture. Our results suggest that the magnitude of the impact of soil amendments on CO2 emissions from Mollisols primarily depends on the type of organic amendments applied, whereas the application rate has limited impacts.

► Applications of organic amendments plus NPK accelerated CO2 emissions from Mollisols.
► The model log(f) = a + b T log(W) explained 50–88% of seasonal variation in CO2 flux.
► Soil CO2 emission was affected more by applied treatments than by soil micro-climate.
► Organic amendment type has larger impact on CO2 emissions than the application rate.