Grassland rehabilitation significantly increases soil carbon stocks by reducing net soil CO₂ emissions

Abstract

Restoration of degraded grasslands through improved management is among the possible sustainable solutions to compensate for anthropogenic soil carbon (C) emissions. While several studies have shown a positive effect of rehabilitation on soil C, the impact on soil CO2 emissions is still uncertain. Therefore, this study aimed at quantifying the impact of grassland rehabilitation on soil CO2 emissions in a degraded grassland, South Africa. Commonly used rehabilitation practices were considered, that is rotational grazing (RG), livestock exclosure with fertilizer application (EF) and annual burning (AB), all being compared with traditional free grazing (FG). A total of 2880 in situ measurements of CO2 emissions were performed over 2.5 years under field conditions simultaneously with aboveground biomass, soil temperature, water content and soil organic C (SOC) to understand the changes in C fluxes. The RG performed the best under degraded grasslands by decreasing net CO2 emissions (per g of C) by 17% compared to FG, while EF increased emissions by 76% and AB had similar emissions to FG. The lower net emission under RG is associated with an increase in SOC stocks by 50% and aboveground biomass by 93%, after three years of implementation. Soil CO2 emissions were correlated positively to aboveground biomass and topsoil temperature (r = 0.91 and 0.60, respectively), implying a high effect of grass cover on soil microclimate and microbial activity. These results suggested RG as a potential cost‐effective nature‐based soil management strategy to increase SOC stocks into degraded grassland. However, long‐term trials replicated in different environments are still required.

Role of biochar toward carbon neutrality

“…Recent attempts have been made to reduce organic carbon loss from soils for climate change mitigation, whose measures include crop residue incorporation (Lupwayi et al 2022;Zhu et al 2022a), organic matter stabilization with clay and metal oxides (Baumann et al 2022;Di et al 2022), fertilizer application (da Silva et al 2022;Gasser et al 2022;Qiu et al 2022;Thakur et al 2022;Zhang et al 2022b), reduced or conservational tillage (Ferrara et al 2022;He et al 2022a;Islam et al 2022), rotational grazing (Abdalla et al 2022;Dong et al 2021), silvopastoral system (Aryal et al 2019;Valenzuela Que et al 2022), and ecological restoration (Howson et al 2022;Wang et al 2020b;Zhao et al 2022). Among them, application of biochar is a promising one due to simultaneous achievement of waste management, nutrient delivery, contaminant immobilization, and climate change mitigation.…”

Soil health and ecosystem services

“…Land degradation from agricultural practices results in significant loss of soil carbon stock. Grassland accounts for nearly 70% of global agricultural land, and its mismanagement has led to the loss of approximately 300 GtC in grassland soil (Abdalla et al, 2022). Peatland represents one of the most carbon rich and fertile soils on earth, storing 30% of global soil carbon; but drainage and intensive cultivation has resulted in a huge loss of peat (Matysek et al, 2022).…”

“…Sustainable agricultural practices, such as rotational grazing in grassland and residue return in cropland, can significantly reduce net CO 2 emission and increase soil carbon stock (Abdalla et al, 2022; Islam et al, 2022). The wastage of peat can be regulated by careful water‐table management, but it also causes trade‐offs among respiratory loss of carbon, CH4 emission and plant productivity (Matysek et al, 2022).…”