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

Abstract

Ridge–furrow mulching system (RFMS) is widely used in arid and semi–arid areas, but its effect on soil respiration (Rs) and its components, including heterotrophic (Rh) and autotrophic respiration (Ra) 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 Rh to Rs. 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 Rs and its components. The ridge soils exhibited much higher Rs (3.43 μmol m–2 s–1) than the furrow soils (2.98 μmol m–2 s–1) under all three RFMS practices. The contribution ratios of Rh to Rs across the different practices ranged from 50.4% to 59.6%. Soil temperature rather than soil moisture explained the seasonal variation of Rs and its components for both CK and RFMS. Nonetheless, high Rs and Rh 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.