A global meta‐analysis of the impacts of no‐tillage on soil aggregation and aggregate‐associated organic carbon

Abstract

No‐tillage (NT) has been shown to control soil degradation by impacting soil aggregates (i.e., basic units of soil structure, whose characteristics mediate key soil processes, like carbon sequestration). However, there has been no systematic analysis of the impacts of NT on soil aggregation and aggregate‐associated soil organic carbon (SOC) at global level. We conducted a global meta‐analysis of 89 publications to elucidate the changes in soil aggregation and aggregate‐associated SOC under NT. Notably, we quantified the roles of diverse environmental and agronomic factors (e.g., climatic conditions, experimental duration, cropping intensity, soil texture, and initial SOC/pH) in the changes in those variables. Relative to conventional tillage (CT), NT significantly increased the proportions of water‐stable large (LM) and small (SM) macro‐aggregates and the mean weight diameter (MWD) (by 49%, 11%, and 23%, respectively) but decreased the proportions of micro‐aggregates (MIC) and silt plus clay‐size particles (SC) (by 11% and 16%, respectively). NT significantly enhanced SOC concentrations in LM (17%), SM (14%), MIC (10%), and SC (7%) compared to CT. Furthermore, the random forest (RF) model demonstrated that climatic conditions, experimental duration, and soil texture were the predominant factors controlling the changes in aggregation and aggregate‐associated SOC under NT. Overall, our results indicate that NT is an effective strategy to enhance soil aggregation and aggregate‐associated SOC, yet variations in responses are determined by specific environmental/agronomic factors. This study provided a basis for identifying site‐specific NT practice that could help improve soil structure and SOC sequestration, ultimately controlling soil degradation in croplands.

Nitrogen addition mediates the effect of soil microbial diversity on microbial carbon use efficiency under long‐term tillage practices

“…In this study, the highest N application rate (210 kg N ha −1 ) could induce toxicity, resulting in lesser microbial diversity. In addition, CT had lower soil SOC (Li et al, 2010; Liu et al, 2021) and C/N ratio compared with NT (Fiorini et al, 2020), which leads to carbon limiting for microorganisms. Hence, the effect of N application had a smaller effect on microbial diversity under CT than NT.…”

Short-term but not long-term perennial mugwort cropping increases soil organic carbon in Northern China Plain

“…The observations of positive and quadratic relationships of SOC with root biomass and aboveground biomass, respectively ( Figures 4A, B ) support the above discussion. In addition, less tillage associated with conversion from annual crops (Y0) to perennial mugwort could decrease the fragmentation of soil aggregates and thus decomposition of soil organic matters ( Liu et al., 2021b ; Kan et al., 2022 ; Lessmann et al., 2022 ; Mondal and Chakraborty, 2022 ), which can increase the storage of SOC. Moreover, it has been documented that enzyme activity plays a vital role in regulating organic carbon in agricultural soils and shows a positive relationship with SOC ( Cattaneo et al., 2014 ; Zhang et al., 2021a ).…”

“…Regression and path analyses showed that there were indirect impacts of aboveground biomass on SOC through affecting root biomass and thus AG and BG activities (Figures 4, 6). In addition, given the important role of pH in regulating C mineralization (Kemmitt et al, 2006;Zhang et al, 2021b), increased pH associated with decreased soil total N could stimulate soil respiration (C mineralization process) and consequently reduce SOC under long-term mugwort cropping (Figures 1, 3, 6), which is consistent with that found in a recent study (Lu et al, 2022). Irrespective of the temporal impacts of mugwort cropping on SOC, the contributions of C-degrading hydrolytic enzyme activities (i.e., AG and BG) and soil (e.g., TN and TP, Figure 5) were greater than those of biotic factors (aboveground and root biomass) on SOC along the chronosequence cropping.…”

Nitrogen addition mediates the effect of soil microbial diversity on microbial carbon use efficiency under long-term tillage practices

“…In this study, high N application rate (210 kg N ha -1 ) could induce toxicity, resulting in lesser microbial diversity. In addition, CT had lower soil SOC (Liet al , 2010;Liu et al , 2021) and C/N ratio compared with NT (Fiorini et al , 2020), which leads to carbon limiting for microorganisms. Hence, the effect of N application had a smaller effect on microbial diversity under CT than NT.…”