Digging deeper: A holistic perspective of factors affecting soil organic carbon sequestration in agroecosystems

Abstract

The global magnitude (Pg) of soil organic carbon (SOC) is 677 to 0.3-m, 993 to 0.5-m, and 1,505 to 1-m depth. Thus, ~55% of SOC to 1-m lies below 0.3-m depth. Soils of agroecosystems are depleted of their SOC stock and have a low use efficiency of inputs of agronomic yield. This review is a collation and synthesis of articles published in peer-reviewed journals. The rates of SOC sequestration are scaled up to the global level by linear extrapolation. Soil C sink capacity depends on depth, clay content and mineralogy, plant available water holding capacity, nutrient reserves, landscape position, and the antecedent SOC stock. Estimates of the historic depletion of SOC in world soils, 115-154 (average of 135) Pg C and equivalent to the technical potential or the maximum soil C sink capacity, need to be improved. A positive soil C budget is created by increasing the input of biomass-C to exceed the SOC losses by erosion and mineralization. The global hotspots of SOC sequestration, soils which are farther from C saturation, include eroded, degraded, desertified, and depleted soils. Ecosystems where SOC sequestration is feasible include 4,900 Mha of agricultural land including 332 Mha equipped for irrigation, 400 Mha of urban lands, and ~2,000 Mha of degraded lands. The rate of SOC sequestration (Mg C ha year ) is 0.25-1.0 in croplands, 0.10-0.175 in pastures, 0.5-1.0 in permanent crops and urban lands, 0.3-0.7 in salt-affected and chemically degraded soils, 0.2-0.5 in physically degraded and prone to water erosion, and 0.05-0.2 for those susceptible to wind erosion. Global technical potential of SOC sequestration is 1.45-3.44 Pg C/year (2.45 Pg C/year).

Managing for soil carbon sequestration: Let’s get realistic

“…Smith et al () estimate 1.6 Pg C/year as the maximum potential for enhanced agricultural management to mitigate CO 2 emissions to the atmosphere, whereas Zomer, Bossio, Sommer, and Verchot () estimate potential storage of 0.90–1.85 Pg C/year in croplands. At 2.45 Pg C/year, a recent new estimate by Lal () is slightly more optimistic. A separate analysis by scientists organized by the Nature Conservancy suggests that better soil management, within economic constraints, might store 0.41 Pg C/year, about 16% of the technical potential and only a small fraction (~4%) of our current fossil fuel emissions (Griscom et al, ).…”

Changes in Storage and the Stratification Ratio of Soil Organic Carbon under Different Vegetation Types in Northeastern China

“…Previous studies on SOC changes responding to different management practices mainly focused on the topsoil due to the higher SOC concentration and the sensitive responses of SOC to environmental changes at this soil depth [32]. However, many more studies reported that focusing on subsoil would give an accurate estimation of changes in SOC concentration and storage [33,34]. Our study showed that the SOCS at 0-20 cm depth in the LEY, PUC, ECH, SUA, and CHL treatments accounted for 60.567%, 62.669%, 54.627%, 58.668%, and 57.467%, respectively, of total SOCS at the 0-50 cm depth (Table 3).…”

Organic amendment additions to rangelands: A meta‐analysis of multiple ecosystem outcomes

“…Interest in organic amendment application to rangelands has been increasing in parallel to soil health efforts in croplands, bolstered by growing interest in using these materials to restore degraded rangelands, a need that may expand as global changes increasingly challenge these lands (Huang et al, ). However, practices seeking to increase soil C might be less effective on untilled rangelands than on croplands, pastures, or restoration sites such as abandoned mines, since prior soil disturbance of most cropland, pasture, or restoration sites would decrease soil C pools, enabling greater proportional increases in soil C pools following amendments (Lal, ; Larney & Angers, ). In general, the efficacy and outcomes of this practice on rangelands are relatively poorly studied, and the potential for negative environmental consequences are higher in rangelands than croplands due to their starkly different ecology and management context, as detailed below.…”