How does tillage intensity affect soil organic carbon? A systematic review

Abstract

Background: The loss of carbon (C) from agricultural soils has been, in part, attributed to tillage, a common practice providing a number of benefits to farmers. The promotion of less intensive tillage practices and no tillage (NT) (the absence of mechanical soil disturbance) aims to mitigate negative impacts on soil quality and to preserve soil organic carbon (SOC). Several reviews and meta-analyses have shown both beneficial and null effects on SOC due to no tillage relative to conventional tillage, hence there is a need for a comprehensive systematic review to answer the question: what is the impact of reduced tillage intensity on SOC? Methods:We systematically reviewed relevant research in boreo-temperate regions using, as a basis, evidence identified within a recently completed systematic map on the impacts of farming on SOC. We performed an update of the original searches to include studies published since the map search. We screened all evidence for relevance according to predetermined inclusion criteria. Studies were appraised and subject to data extraction. Meta-analyses were performed to investigate the impact of reducing tillage [from high (HT) to intermediate intensity (IT), HT to NT, and from IT to NT] for SOC concentration and SOC stock in the upper soil and at lower depths.Results: A total of 351 studies were included in the systematic review: 18% from an update of research published in the 2 years since the systematic map. SOC concentration was significantly higher in NT relative to both IT [1.18 g/ kg ± 0.34 (SE)] and HT [2.09 g/kg ± 0.34 (SE)] in the upper soil layer (0-15 cm). IT was also found to be significant higher [1.30 g/kg ± 0.22 (SE)] in SOC concentration than HT for the upper soil layer (0-15 cm). At lower depths, only IT SOC compared with HT at 15-30 cm showed a significant difference; being 0.89 g/kg [± 0.20 (SE)] lower in intermediate intensity tillage. For stock data NT had significantly higher SOC stocks down to 30 cm than either HT [4.61 Mg/ ha ± 1.95 (SE)] or IT [3.85 Mg/ha ± 1.64 (SE)]. No other comparisons were significant. Conclusions:The transition of tilled croplands to NT and conservation tillage has been credited with substantial potential to mitigate climate change via C storage. Based on our results, C stock increase under NT compared to HT was in the upper soil (0-30 cm) around 4.6 Mg/ha (0.78-8.43 Mg/ha, 95% CI) over ≥ 10 years, while no effect was detected in the full soil profile. The results support those from several previous studies and reviews that NT and IT increase SOC in the topsoil. Higher SOC stocks or concentrations in the upper soil not only promote a more productive soil with higher biological activity but also provide resilience to extreme weather conditions. The effect of tillage practices on total SOC stocks will be further evaluated in a forthcoming project accounting for soil bulk densities and crop yields. Our findings can hopefully be used to guide policies for sustainable management of agricultural soils.

The multifunctional roles of vegetated strips around and within agricultural fields

“…Polygon area corresponds to the number of studies using the term studies per year. Whilst many other systematic reviews and maps have identified exponential growth in research publications over recent decades [73][74][75], publication rates within the topic of this review appear to be more linear, increasing from a minimum of approximately 5/ year in 1990 at the rate of c. 2.7 studies per year from that point onwards. This suggests a more stable growth in research on the topic.…”

A global meta‐analysis of soil organic carbon response to corn stover removal

“…Many meta-analyses show that management practices such as residue removal, fertilization, and rotational diversification and study duration will affect SOC sequestration (Anderson-Teixeira, Davis, Masters, & Delucia, 2009;Chivenge, Vanlauwe, & Six, 2011;Haddaway et al, 2017;Han, Zhang, Wang, Sun, & Huang, 2016;Liu, Lu, Cui, Li, & Fang, 2014;Qin, Dunn, Kwon, Mueller, and Wander (2016b); West & Post, 2002), but there is a lack of robust quantitative synthesis of the empirical evidence (Schmer, Stewart, & Jin, 2017;Wilhelm et al, 2004). Furthermore, previous meta-analyses have evaluated the effect of different management practices (e.g., tillage) on SOC for crop production studies, few focused on evaluating corn residue impacts.…”

Drivers of soil carbon stabilization in oil palm plantations

“…Policymakers have recently acknowledged the promotion of soil C sequestration in agroecosystems as a promising strategy to simultaneously mitigate climate change and enhance food security (Lal, ). Nonetheless, management practices favouring soil C sequestration lead to highly variable outcomes, calling for a deeper understanding of processes and factors controlling C stabilization, especially after land‐use changes (Ghimire, Lamichhane, Acharya, Bista, & Sainju, ; Haddaway et al, ). This is particularly needed in regions that are undergoing rapid and substantial land degradation following conversion from largely forested landscapes to intensive agricultural systems, as has been the case in tropical landscapes dominated by oil palm ( Elaeis guineensis ) plantations.…”