Biocrust as a nature-based strategy (NbS) to restore the functionality of degraded soils in semiarid rainfed alfalfa (Medicago sativa L.) field

Abstract

Biological soil crust (BSC) establishment as a nature-based strategy (NbS) may restore the functionality of degraded soils in semiarid agroecosystems. However, this issue is little documented. To address this issue, a BSC-inoculated (broken-skin inoculation, moss) field experiment was conducted in a semiarid alfalfa (Medicago sativa L.) field in 2018 and 2019, with the treatments as follows: 1) conventional flat planting (control), 2) flat planting with BSC inoculation (BSC), 3) ridge-furrow planting (RF) and 4) sectional ridge-furrow planting (SRF). The result showed that compared with the control, alfalfa biomass was evidently increased in BSC, RF and SRF treatments at the second growing season. Relative to the control, the BSC treatment harvested the highest soil total porosity, mean weight diameter, and macroaggregate proportion (>2 mm) (p < 0.05; significantly greater than RF and SRF). Also, the BSC inoculation remarkably improved soil microbial biomass carbon (C) & nitrogen (N), soil organic C and total N by 46%, 35%, 16% and 29% respectively, also significantly greater than RF and SRF (p < 0.05). This phenomenon was tightly correlated with the optimized soil C fractions as affected by the BSC inoculation, since dissolved organic C, oxidizable organic C, particulate organic C, light fraction organic C and heavy fraction organic C were promoted by 17%, 29%, 13%, 40% and 14% in the BSC treatment respectively, relative to the control (p < 0.05). Therefore, the BSC inoculation significantly improved soil quality in alfalfa field. This outcome was closely associated with the increased soil cohesion and microaggregate proportion, and decreased soil C-N ratio under the BSC. The optimized physiochemical properties boosted C mineralization and the utilization of soil C & N by microbial organisms. Therefore, the BSC establishment can act as a promising NbS to conserve the degraded soils in semiarid agroecosystems.