Effects of ridge-furrow mulching on soil CO2 efflux in a maize field in the Chinese Loess Plateau

Ridge-furrow mulching system (RFMS) is widely used in arid and semi-arid areas, but its effect on soil respiration (R-s) and its components, including heterotrophic (R-h) and autotrophic respiration (R-a) are still poorly understood. In this study, CO2 flux from the soil of furrows and ridges was measured across different RFMS practices (i.e., three different ridge/furrow ratios) and conventional flat planting (CK). A trenching method was used to estimate the contribution of R-h to R-s. Compared with CK, RFMS significantly increased soil temperature of the ridge, promoted soil moisture of the furrow, and enhanced microbial diversity at the early crop growth stage, resulting in increased R-s and its components. The ridge soils exhibited much higher R-s (3.43 mu mol s(-1)) than the furrow soils (2.98 mu mol m(-2) s(-1)) under all three RFMS practices. The contribution ratios of R-h to R-s across the different practices ranged from 50.4% to 59.6%. Soil temperature rather than soil moisture explained the seasonal variation of R-s and its components for both CK and RFMS. Nonetheless, high R-s and R-h values in RFMS did not induce a decline of soil organic carbon during the two-year experimental period. Improved root growth in RFMS practices may provide more exudates to the soil, thus offsetting soil carbon decomposition. Compared with CK, RFMS with ridge/furrow ratios of 40:70 cm, 55:55 cm, and 70:40 cm, significantly increased soil CO2 emissions by 10.6%, 19.6%, and 20.4%, respectively, while increasing maize yield by 26.1%, 36.4%, and 50.3%, respectively. Carbon emission efficiency (CEE) was significantly higher in RFMS than in CK in both years. This study suggests that, due to its high CEE, RFMS with a ridge/furrow ratio of 70:40 cm could be a highly promising strategy for sustaining crop productivity while minimizing environmental impacts.