Management-induced changes in soil organic carbon on global croplands

Abstract

Abstract. Soil organic carbon (SOC), one of the largest terrestrial carbon (C) stocks on Earth, has been depleted by anthropogenic land cover change and agricultural management. However, the latter has so far not been well represented in global C stock assessments. While SOC models often simulate detailed biochemical processes that lead to the accumulation and decay of SOC, the management decisions driving these biophysical processes are still little investigated at the global scale. Here we develop a spatially explicit data set for agricultural management on cropland, considering crop production levels, residue returning rates, manure application, and the adoption of irrigation and tillage practices. We combine it with a reduced-complexity model based on the Intergovernmental Panel on Climate Change (IPCC) tier 2 method to create a half-degree resolution data set of SOC stocks and SOC stock changes for the first 30 cm of mineral soils. We estimate that, due to arable farming, soils have lost around 34.6 GtC relative to a counterfactual hypothetical natural state in 1975. Within the period 1975–2010, this SOC debt continued to expand by 5 GtC (0.14 GtC yr−1) to around 39.6 GtC. However, accounting for historical management led to 2.1 GtC fewer (0.06 GtC yr−1) emissions than under the assumption of constant management. We also find that management decisions have influenced the historical SOC trajectory most strongly by residue returning, indicating that SOC enhancement by biomass retention may be a promising negative emissions technique. The reduced-complexity SOC model may allow us to simulate management-induced SOC enhancement – also within computationally demanding integrated (land use) assessment modeling.

Contributions of plant breeding to soil carbon storage: Retrospect and prospects

“…In Canada, soil organic C stocks in the surface 20 cm were estimated to increase at a rate of 10.6 Tg C yr −1 between 2005 and 2015, primarily due to increasing crop yield and associated residue inputs (Fan et al, 2019). In addition, Karstens et al (2020) estimated that the increase in crop productivity led to an increase in global cropland soil organic C stocks between 1975 and 2010, at a rate of 0.11 Pg C yr −1 . This study used harvest index values that varied based on crop yield, and root:shoot ratios that were held constant for each species.…”

“…Factors such as grain drying costs, field operability, labor constraints, crop genetic availability, and marketing practices, appear to more strongly impact farmer decision‐making than thermal availability (Abendroth et al., 2021). While increased crop residue return is expected to increase soil organic C, this will not be the case if the residues are instead harvested for fuel, feed, or material use (Karstens et al., 2020). The potential for cover crop breeding to overcome barriers to cover crop adoption will only be realized if farmers are willing to pay for improved seed.…”

“…In addition, Karstens et al. (2020) estimated that the increase in crop productivity led to an increase in global cropland soil organic C stocks between 1975 and 2010, at a rate of 0.11 Pg C yr −1 . This study used harvest index values that varied based on crop yield, and root:shoot ratios that were held constant for each species.…”

A global dataset for the production and usage of cereal residues in the period 1997–2021

“…NO 3 − ) 23 , 27 . Currently, crop models, which are a common tool for such assessments, typically assume a globally uniform fraction of crop residues left on the field 28 – 31 , and assess changes in crop residue management relative to this uniform baseline 32 – 34 (although some models do have inbuilt ways of estimating crop residue return 35 – 37 ). Incorporating our dataset into regional and global modelling will thus lead to better identification of areas that are hotspots for environmentally harmful losses (e.g.…”

A Scientometric Analysis of Research Trends and Knowledge Structure on the Climate Effects of Irrigation between 1993 and 2022

“…Although the number of publications on CEI was not abundant in the stages of knowledge germination and knowledge accretion, the milestone papers on land management changes and irrigation experiments assisted in the development of various research topics during the knowledge prosperity period. For example, the global map of irrigation areas [72], and the irrigation cooling effects studies [18] play an important role in evaluating and constructing global hydrological models, ecosystem models, crop models and climate models by considering agricultural management measures or human land management [24,[81][82][83] activities. Ecology, earth, and marine can be considered the most influential disciplines of research in this field, and they have been influenced by earth, geology, geophysics and plant, ecology, zoology.…”