Observed differences between paddy and upland croplands in soil organic carbon (SOC) and soil inorganic carbon (SIC) may reflect environmental and data-provenance imbalances rather than land-use effects. We reconstructed independent SOC and SIC profile datasets across China, harmonized depths, and separated full-sample comparisons from a prespecified comparable subset. Among all topsoil SOC profiles retained after applying the inclusion criteria (334 paddy, 347 upland), the median Upland-minus-Paddy contrast was −2.12 g kg−1; within the shared subset (97/95), it attenuated to −0.35 g kg−1 (95% interval, −1.74 to 1.55). For 97 paddy soils, changing only the land-use indicator to upland while holding observed soil and environment states fixed yielded a mean SOC contrast of −0.58 g kg−1 (joint 95% interval, −1.02 to −0.15), with 78.4% negative. A layer-resolved Extra Trees S-learner supported this scenario with out-of-fold R2 = 0.72 and mean R2 = 0.72 across ten spatial partitions. The shared topsoil SIC subset retained only 9 paddy and 7 upland profiles, so adjusted SIC could not be estimated. Aridity index (AI) stratification showed the strongest negative SOC contrast in more humid high-AI croplands (−1.08 g kg−1; −1.62 to −0.56), whereas low- and middle-AI strata crossed zero; the high-minus-middle difference was −1.29 g kg−1 (−2.09 to −0.60). Among comparable croplands, observed topsoil SOC differed little between paddy and upland fields, but model predictions indicated lower SOC under upland land use, particularly in humid regions. These results suggest a modest SOC advantage of paddy croplands, while SIC differences remain unresolved.

Soil organic carbon (SOC) sustains ecosystem productivity, soil health, and sequesters atmospheric CO2. Straw return (StrawR) effectively compensates for carbon (C) losses by SOC mineralization in croplands. Quantifying the straw-derived SOC and straw conversion efficiency (SCE; the percentage of straw C converted to SOC) enables a direct assessment of C sequestration potential. This study integrates 13C isotopic tracer data with machine learning approaches to evaluate straw-derived SOC and SCE. A random forest model was further used to identify the key environmental and management drivers controlling straw-derived SOC and SCE, and to extrapolate their spatial patterns at the global scale. Straw-derived SOC content decreased over time, primarily due to the relative accumulation of recalcitrant compounds. Such dynamics are typically mediated by changes in microbial metabolic strategies in response to shifting resource availability. Random forest analysis identified StrawR amount, straw particle size, and soil bulk density (BD) as the key drivers of straw-derived SOC content (IncMSE percentages: 42%, 20%, and 19%, respectively). High soil BD potentially reduces soil aeration and suppresses microbial metabolic capacity, reducing C sequestration. Machine learning predictions indicate a straw C residual ratio of 17 ± 3.4% after 1 year and a global average SCE of 10 ± 1.1% after 5 years of StrawR, which supports our hypothesis that initial StrawR practices elevated C sequestration potential and SCE compared with prolonged StrawR application. Assuming 100% global adoption, StrawR offers a theoretical maximum biophysical potential of 1.7 Pg C yr−1 over five years. This maximum capacity would theoretically offset 52% of agricultural CO2 emissions and 16% of total anthropogenic CO2 emissions. This study addresses critical gaps in straw conversion dynamics and updated estimates of C sequestration capacity, highlighting the contribution of StrawR as a climate change mitigation strategy.

Temperature sensitivity (Q(10)) of soil organic carbon (SOC) mineralization is crucial for understanding dynamics of soil C-climate feedback and SOC sequestration. Differentiating between SOC fractions, such as particulate organic matter (POM) and mineral-associated organic matter (MAOM), can enhance our understanding of C dynamics under global change. However, studies focusing on these processes, especially in high-clay Vertisol agroecosystems remain limited. To address this gap, we leveraged a 56-year long-term experiment examining the impacts of different management practices on SOC mineralization and Q(10) of these fractions. The treatments included tillage (no-till, NT vs. conventional tillage, CT), residue management (residue retention, RR vs. residue burned, RB), and fertilization (0, N0 and 90 kg N ha(-1), N90) in a randomized complete block design. A 63-day incubation was conducted at 15 degrees C and 25 degrees C for the bulk soil, POM and MAOM to assess how these treatments influence SOC mineralization and Q(10) dynamics. We found that SOC mineralization rates followed the order: POM > bulk soil > MAOM. In the bulk soil, Q(10) was significantly higher in RR than RB, but remained significantly lower than that of POM and MAOM. Q(10) of POM was significantly reduced under NT during the early stage (first 21 days), and N90 in the late stage (21-63 days) of incubation. Correlation analysis and structural equation modeling showed that the C:N ratio and pH mediated management effects on mineralization. Substrate availability strongly affected Q(10) of MAOM (and the bulk soil, which contained 96.7 % MAOM in total soil mass), while C quality (C:N ratio) was the primary driver for Q(10) of POM in this high-clay Vertisol. This study highlights the importance of considering not only bulk SOC but also SOC fractions when evaluating mineralization and Q(10) dynamics. Our findings suggest that focusing on specific SOC fractions and management practices can improve long-term C sequestration under different agricultural regimes.

Conservation tillage combined with legume-based crop rotations (CT-LB) has gained global recognition as a climate-smart agricultural practice for its potential to enhance soil organic carbon (SOC) sequestration. However, the synergistic effects and underlying mechanisms by which CT-LB promote SOC accumulation remain unclear. This study conducted, a global meta-analysis, utilizing data from 86 field trials across 78 publications, to unveil the interaction effects of conservation tillage (CT) combined with legume-based crop rotations (LB) on SOC sequestration. The results showed that CT and LB individually increased SOC by 5.25 % and 2.21 %, respectively, while their combined application (CT-LB) led to a synergistic increase of 9.76 % compared to traditional tillage with non-legume rotation using the same main crop (TT-TL). The SOC enhancement under CT-LB was strongly correlated with total nitrogen (TN, R-2 = 0.73), aggregates (> 0.25 mm) (SA(>0.25), R-2 = 0.89), alkaline phosphatase (ALP, R-2 = 0.89), and light fraction organic carbon (LFOC, R-2 = 0.94). Specifically, the capacity of CT to enhance SOC can be improved by LB through the following mechanisms: 1) increasing total nitrogen (TN, + 18.28 %) and reducing the soil carbon: nitrogen ratio (C:N, -12.22 %) to increase residue retention and degradation, 2) improving microbial activity (SMBC +15.28 %) and enzyme activity (+ 19.56 %) to facilitate returned crop residue decomposition, and 3) promoting soil aggregation (+ 14.54 %) to encapsulate SOC. Additionally, variations exited in the interaction effects of SOC under CT-LB systems among site-specific conditions. In warmer (> 18 degrees C) areas with initially low TN (< 1 g/kg), SOC (< 10 g/kg), and high bulk density (BD) (>1.3 g/cm(3)), the positive interaction effects were enhanced. Maximizing this synergistic effect could potentially increase global SOC sequestration by 0.06-0.19 Mg ha(-1)yr(-1). These findings underscore the critical importance of aligning CT-LB practices with site-specific conditions to fully realize their potential for climate change mitigation.

Straw incorporation enhances soil organic carbon (SOC) sequestration. However, the microbial processes associated with stabilization of root- and shoot-derived carbon (C) under long-term tillage remain unclear. We combined a field experiment initiated in 2008 with a two-year in situ incubation of ¹³C-labelled wheat and maize root and shoot residues under no-tillage (NTS), conventional plow tillage (CTS), and rotary tillage (RTS). Residue-derived C in SOC, particulate organic carbon (POC), and mineral-associated organic carbon (MAOC) was quantified. Microbial genes involved in carbon, nitrogen, and phosphorus cycling and their co-occurrence networks were also characterized. In 2024–2025, across tillage practices, mean root C residual ratios exceeded shoot residual ratios by 8.3–12.7% in wheat and 9.2–41.1% in maize. Across both crops, the contribution of root-derived C to soil MAOC was greater than its contribution to soil POC. Tillage effects depended on crop and SOC fraction. In wheat, NTS produced the highest root-derived POC in 2025. During 2024–2025, wheat root-derived MAOC was higher under CTS than NTS. In maize, root-derived MAOC was higher under RTS than CTS. Maize-derived POC did not differ among treatments. NTS increased several C-cycling gene groups and exhibited the strongest functional connectivity. Genes involved in chitin degradation were negatively associated with POC. Genes involved in starch and nitrogen degradation were positively associated with POC and negatively associated with MAOC. These findings indicate distinct stabilization patterns for root and shoot inputs. Long-term tillage was associated with changes in residue-derived C partitioning and microbial functional networks.

The mineralization of soil organic carbon (SOC) profoundly impacts the efficiency of SOC sequestration, crucial for the long-term stable carbon (C) sequestration in soil. Despite its significance, systematic studies investigating the effects of three pillars of conservation agriculture (CA), i.e., no-till, residue retention (RR), and crop rotation (CR), on the mineralization of SOC remain scarce. To address the gap, we conducted a comprehensive analysis, collating data from 89 experimental sites worldwide and integrating with field experimental data sampled from 10 sites across China. Our study evaluated potentially mineralizable carbon (PMC) using first-order kinetic fitting, and specific PMC (SPMC, PMC/SOC) to elucidate patterns of SOC mineralization under CA and its moderation by climatic, environmental, and soil factors. The results showed a gradual decrease in PMC with the adoption of increasing numbers of CA pillars, with the full implementation reducing PMC by 35.1%. The impact of no-till on PMC and SPMC was not significant, while RR and CR significantly increased and decreased PMC by 21.0% and 27.3%, respectively. Notably, only CR significantly increased SPMC by 15.0%. The findings suggest that under CR, PMC exhibit reduced sensitivity to climatic and environmental changes and emphasizing higher environmental stability of SOC. Soil microbial indicators demonstrated direct and indirect positive regulatory effects on PMC, and SPMC is positively affected by MBC in addition to SOC, both of which indicate the vital role of soil microbes in regulating SOC mineralization. We proposed a conceptual model highlighting nonlinear relationship between stable SOC pool and SOC, emphasizing how the relationship between C sequestration and emission reduction can be optimized under CR. Further research should delve into understanding microbial pathways in SOC mineralization and their role in balancing mineralization and sequestration.

Transferring photosynthetic C to soil organic C (SOC) via rhizodeposition is essential for soil health and soil C sequestration. This study employed 13C isotope labeling to quantify rhizodeposition C transfer and examined its relationship with soil properties and microbial communities in a 15-year long-term tillage experiment. The treatments included no-tillage (NTS), plow tillage (CTS), and rotary tillage (RTS), all implemented with straw return. The results showed that the rhizodeposition C transfer and microbial community compositions varied between wheat and maize. Rhizosphere-specific taxa, such as Galbitalea in wheat and Priestia in maize, were enriched under NTS. Compared to CTS, RTS increased rhizosphere 13C-SOC by 65% in wheat, while NTS increased it by 99% in maize, thereby enhancing rhizodeposition C transfer. Furthermore, NTS facilitated fungal community stability and DOC turnover, collectively promoting rhizodeposition C transfer. Optimizing crop-specific tillage strategies can enhance C transfer, improve soil health, and mitigate climate change.

Conservation agriculture (CA), based on principles of conservation tillage (CT) and crop rotations, has been adopted as a solution to global climate change. However, interactions between these principles and their cumulative effects on soil functions and crop productivity are not yet fully understood. Herein, a 4-year filed experiment was conducted to assess the impact of CA on soil ecosystem multifunctionality (EMF) in the North China Plain (NCP). The results showed that CA improved EMF by up to 532 % compared to traditional agriculture (rotary tillage under wheat and maize rotation system). This enhancement is mainly driven by a 12.3 % increase in soil organic carbon (SOC) storage, an 8.3 % reduction in soil carbon to nitrogen ratio (C: N), a 68.3 % boost in soil enzyme activities index (SEI), and a 59.7 % increase in available phosphorus (AP) under legumebased crop rotations (LBCR) compared to maize-wheat-maize-wheat (MWMW). The principle of CT improved soil physical structure, enhancing soil aggregate stability by up to 38.1 % compared to rotary tillage (RT). Although, the benefits of CT on crop yield were not always observed, positive interactions on crop yield occurred under LBCR combined with CT. For instance, the soybean-wheat-soybean-wheat (SWSW) rotation produced 40.8 % higher yields than the MWMW rotation under CT. Overall, benefits of CT in improving soil structure, along with the increased diversity crop residues, adjustments in soil nutrient stoichiometric ratios, and enhanced soil enzyme activity under LBCR, led to improved SOC sequestration, crop yield and EMF under CA. The positive interactions between the principles of CA demonstrate its ability to enhance ecosystem multifunctionality. As a result, the combination of CT and LBCR within CA is recommended to sustain the productivity in NCP and other regions with similar conditions.

Global climate change is constraining the practices of agricultural production due to which developing climatesmart agriculture (CSA) faces enormous challenges in mitigating greenhouse gas (GHG) emissions and ensuring food security. Currently, few studies have systematically reviewed the progress of CSA in developing dryland agriculture in China. This chapter reviews the problems and challenges in CSA practices of China's dryland farming. The application of CSA management practices in China's dryland can increase the amount of soil-organic carbon (SOC) and maintain or increase crop yield, but GHG emissions remain controversial. Adaptation to climate change can be addressed by adopting conservation tillage, optimizing fertilizer application, and improving technologies, such as straw conversion into biochar. Future research should consider the combined plant-soil-climate system when developing CSA management practices in dryland agricultural systems to prioritize the achievement of synergies among soil-quality improvement, increase crop yield, and facilitate climate adaptation.

Soil carbon (C) sequestration, as an important means of mitigating climate change, is influenced by C miner-alization. No-till (NT) and residue retention (RR) developed rapidly due to their soil C sequestration function. However, their effects on soil organic carbon (SOC) mineralization are still controversial, with positive and negative effects under NT and unclear effects on mineralization ratios under RR reported, which hinders the ability to predict SOC sequestration efficiency, SOC stabilization and CO2 emissions. Therefore, a global meta -analysis based on 132 peer-reviewed papers was used to investigate the effects of NT and RR on absolute mineralizable carbon (AMC) and specific mineralizable carbon (AMC per unit SOC, SMC) in laboratory incu-bation studies. The results showed that NT significantly increased AMC in surface (0-5 cm) and subsoil (> 20 cm) where it had been practiced over the long-term (>15 years), without crop rotation, and in alkaline soils (pH >7.8) compared to conventional tillage. RR generally increased AMC, and its negative effect on SMC was sig-nificant in soils with a high input of N fertilizer (> 300 kg N/ha) and sandy soils compared to residue removal. NT significantly reduced SMC in neutral and acidic soils (pH < 7.8), or compared to chisel plow or rotary tillage. Furthermore, RR and NT generally improved soil indicators except ammonium nitrogen and bulk density, and RR improved most of them significantly. The correlation analysis revealed that the change in AMC was significantly positively correlated with the indicators related to C/N, while SMC was significantly negatively correlated with SOC concentration. In general, both NT and RR significantly increased AMC, while SMC increased significantly with RR only, and NT+RR significantly decreased SMC. When combined with other measures, e.g. N application with RR, and applied in combination, NT and RR can increase SOC while decreasing its mineralization, thus improving the sequestration of C.

No-tillage (NT) has obvious advantages in reducing input and labour costs. However, some farmers have raised concerns about adapting continuous NT to manage farmland due to problems such as soil stratification and less yield. Therefore, occasionally targeted tillage (known as strategic tillage, ST) has been proposed as a flexible management measure. To evaluate the potential impact of a typical ST pattern on soil properties and yield, a 12-year positioning field trial was conducted with three tillage practices, including long-term no-tillage (NT), ploughing tillage (CT), and ST (3-year NT and 1-year CT), in an intensive double-cropped rice system in southern China. ST could alter soil physicochemical properties by reducing soil stratification and potentially increasing nutrient availability. ST alleviated the bulk density (BD) stratification caused by the continuous decrease in 0-5 cm BD and the continuous increase in 5-10 cm BD under NT, due to the periodic use of CT. Compared with NT and CT, ST increased the soil available K (AK) and available P (AP) concentrations without affecting the SOC or TN storage throughout the profile. However, ST lowered the soil acidification at the soil surface (0-5 cm) while increasing the risk of soil subsurface acidification. Relative to ST, yields with NT trended lower over time, and the yield gap between NT and ST increased as the experiment progressed. The multiyear average yield of ST was 0.31 t ha-1 higher than that of NT but lower than that of CT. ST had the potential to improve the low yield under NT. It may be related to the fact that the seed setting rate (the proportion of filled to total seeds) of ST was significantly higher than that of NT (p < 0.05). In conclusion, strategic tillage is a more sustainable tillage method than continuous no-tillage and ploughing tillage in double-cropped rice systems in southern China.

Northeast China, the important grain‐producing region in China, is under threat from soil degradation because of long‐term conventional tillage (CT). The adoption of conservation tillage is anticipated to restore soil fertility, maintain crop yields and enhance sustainability. However, the integrated effects of conservation tillage practice on crop yields and soil organic carbon (SOC) remain unclear. In this meta‐analysis of peer‐reviewed studies conducted in the Northeast China region, we assess crop yields and SOC values under no‐till, ridge tillage and subsoiling tillage practices. The results indicate that in areas with mean annual temperatures (MAT) below 3°C, crop yields were significantly (p < .05) higher under ridge tillage (0.8%) and subsoiling tillage (13.1%) compared with CT, whereas yields reduced under no‐till (−3.7%). Ridge tillage generally had a similar effect on crop yield as no‐till, without the negative impact in colder regions. We also report that no‐till practice increased SOC concentrations by 24.1%, 43.9% and 17.4% in areas of higher temperature (MAT > 6°C), low mean annual precipitation (MAP) (<500 mm) and continuous cropping conditions, respectively. Ridge tillage and subsoiling tillage also had positive effects on SOC concentrations (to a lesser degree than no‐till), indicating that conservation tillage can enhance SOC in Northeast China. Overall, the implementation of different conservation tillage measures in Northeast China was found to enhance crop yields and sequester carbon. We recommend that ridge tillage is used in colder areas and that subsoiling tillage is used in rotation with other tillage measures to maintain crop yields.

No‐till (NT) is a sustainable option because of its benefits in controlling erosion, saving labor, and mitigating climate change. However, a comprehensive assessment of soil pH response to NT is still lacking. Thus, a global meta‐analysis was conducted to determine the effects of NT on soil pH and to identify the influential factors and possible consequences based on the analysis of 114 publications. When comparing tillage practices, the results indicated an overall significant decrease by 1.33 ± 0.28% in soil pH under NT than that under conventional tillage ( p < .05). Soil texture, NT duration, mean annual temperature (MAT), and initial soil pH are the critical factors affecting soil pH under NT. Specifically, with significant variations among subgroups, when compared to conventional tillage, the soil under NT had lower relative changes in soil pH observed on clay loam soil (−2.44%), long‐term implementation (−2.11% for more than 15 years), medium MAT (−1.87% in the range of 8–16℃), neutral soil pH (−2.28% for 6.5 < initial soil pH < 7.5), mean annual precipitation (−1.95% in the range of 600–1200 mm), in topsoil layers (−2.03% for 0–20 cm), with crop rotation (−1.98%), N fertilizer input (the same for NT and conventional tillage) of 100–200 kg N ha −1 (−1.83%), or crop residue retention (−1.52%). Changes in organic matter decomposition under undisturbed soil and with crop residue retention might lead to a higher concentration of H + and lower of basic cations (i.e., calcium, magnesium, and potassium), which decrease the soil pH, and consequently, impact nutrient dynamics (i.e., soil phosphorus) in the surface layer under NT. Furthermore, soil acidification may be aggravated by NT within site‐specific conditions and improper fertilizer and crop residue management and consequently leading to adverse effects on soil nutrient availability. Thus, there is a need to identify strategies to ameliorate soil acidification under NT to minimize the adverse consequences.

Low wheat grain yield under conservation tillage has been reported, and growth duration could determine the yield. Thus, an 11-year field experiment was conducted to assess the relationship between growth duration and grain yield under different tillage and residue managements. Four treatments were investigated: no-till with residue removal (NT0), conventional tillage with residue removal (CT0), no-till with residue retention (NTR, conservation tillage), and conventional tillage with residue incorporation (CTR). Beginning at 20 days after anthesis (DAA), NTR significantly increased physiological activities, indicating that NTR had a longer growth duration. NTR significantly prolonged growth duration by 2-3 days compared with the other treatments attributed to delayed emergence of seedlings caused by higher soil compaction and moisture under NTR. The CT0 had the highest grain yield on the standard harvest date used in the local area (36 DAA). Whereas the plants in NTR reached physiological maturity (39 DAA), the grain yield in NTR was significantly increased by 7.8-8.8% compared with yield at 36 DAA, and no significant difference was observed between NTR and CT0 due to the increased thousand kernel weight of NTR. Thus, it is practicable for harvesting at physiological maturity in NTR to obtain higher grain yield.

Improving agro-resource utilization efficiency is essential for developing an environment-friendly agricultural system. The North China Plain (NCP), China's most important food-producing area, is facing severe resource constraints, such as low carbon and water efficiency. Although there have been many studies on single topic, little is known about the comprehensive assessment of carbon and water utilization in the NCP, as well as the economic benefits under different farmland management measures. We assessed the carbon footprint (CF), water use efficiency (WUE), economic benefits, and their cumulative effects in 2014-2015 during the wheat/maize season and throughout the year. Four tillage systems were investigated: no-till with/without residue retention (NTS/NT0) and conventional tillage with/without residue retention (CTS/CT0). The results indicated that residue retention (RR) reduced area-scaled, yield-scaled, and net income-scaled CF of the entire year by 101.56%, 106.88%, and 103.85%, respectively, compared to residue removal (R0; p < 0.05), due to improved SOC stock, crop yield and net income. Seasonal variations in the effects of no-till (NT) on CF were found. The primary sources of CF components were urea and electrical energy, which contributed 10.0%-34.8% and 5.0%-30.0%, respectively, apart from CF derived from changes in SOC stocks. Compared to R0 (p < 0.05), RR could increase WUE by 5.5%-36.4% while also increasing net income. The highest score of a comprehensive evaluation of carbon and water utilization and economic benefits was CTS, NTS, and CTS during wheat, maize season, and the entire year, respectively. The findings from our study site indicated that residue retention could improve not only the carbon and water use efficiency, but also the farmer income. Residue retention seems to be a promising field management strategy for reducing the environmental footprint of agricultural production, alleviating the agricultural resource pressure, and benefiting farmers in the NCP.

The sensitivity of soil organic carbon (SOC) mineralization to temperature could affect the future atmospheric CO2 levels under global warming. Sieved soils are widely used to assess SOC mineralization and its temperature sensitivity (Q10) via laboratory incubation. However, sieved soils cause a temporary increase in mineralization due to the destruction of soil structure, which can affect estimates of SOC mineralization, especially in soils managed with no-till (NT). To identify the effects of soil sieving on SOC mineralization and Q10, soil was collected from an 11-year field experiment under a wheat-maize cropping system managed with a combination of tillage [NT and plow tillage (PT)] and residue [residue returning (RR) and residue removal (R0)]. Soil was either sieved or left in an undisturbed state and incubated at 15 degrees C and 25 degrees C. SOC mineralization in sieved soils at 25 degrees C was 47.28 g C kg-1 SOC, 160.1% higher than SOC mineralization in undisturbed soils (P < 0.05). Interestingly, Q10 values in sieved soils were 1.29, 77.6% lower than Q10 in undisturbed soils (P < 0.05). Highly significant correlations (P < 0.01) were observed between sieved and undisturbed soils for SOC mineralization (r = 0.85-0.98) and Q10 (r = 0.78-0.87). Soil macro-aggregates had lower SOC mineralization by 6.1-21.9%, but higher Q10 values by 4.7-6.5% compared with micro-aggregates, contributing to lower mineralization and higher Q10 under NT and RR. Furthermore, structure equation and random forest modelling showed that increased SOC contents in NT and RR could not only reduce SOC mineralization, but also constrained the improvement of Q10 in NT and RR. Overall, these results indicated that although sieved soils overestimated SOC mineralization and underestimated Q10 due to the destruction of macro-aggregates, the patterns between treatments were similar and sieving soil for incubation is considered as a suitable approach to evaluate the relative impacts of NT and RR on SOC mineralization and Q10. (c) 2021 Elsevier B.V. All rights reserved.

Carbon (C) sequestration in agricultural systems is recommended as a beneficialmeasure for climate change mitigation and food security. Despite much research, the relationship between soil organic carbon (SOC) storage and sustainable crop productivity has not been identified for various agricultural ecosystems, especially in the paddy ecosystem where conservation tillage has been adopted. Thus, a long-term experiment was conducted to evaluate the effects of tillage practices on SOC storage, yield, and their relationship in a double-cropped rice (Oryza sativa L.) paddy in Southern China from2005 to 2018. Four tillage systemswere investigated: no-tillwith residue retained on the soil surface (NTS), rotary tillagewith residue retention (RTS), plowtillage with residue retention (CTS), and plowtillage with residue removed (CT). The SOC accumulation in the 0-20 cm layer in tillage systems included two stages: the rapid accumulation stage (2005-2007) and the slow fluctuation stage (2007-2018), with a tendency for C saturation. After reaching C saturation, the increase in SOC storage was not obvious, even with continued C input, and the SOC storage under different tillage systems was inconsistent. In general, SOC storage under NTS was the greatest. Interannual changes were not significant, while cumulative yield (2005-2018) was highest under CTS (162.13 t ha(-1)), followed by RTS (158.46 t ha(-1)), NTS (153.99 t ha(-1)), and CT (149.70 t ha(-1)). Tillage practices had no effect on the yield stability of late rice, but a significant difference in early ricewas noticed between CTS and RTS. A non-linear relationship between rice yield and SOC storagewas significant (P < 0.0001). With increasing SOC, yields tended to increase first and then decrease. Thus, innovative tillage strategies (such as NTS) could increase SOC storage before it reaches C saturation, but maintaining SOC storagewithin a reasonable range and optimizing SOC distributionmight bemore beneficial for crop productivity than a higher SOC storage, especially in C-rich paddy fields. C() 2020 Elsevier B.V. All rights reserved.

The role of biochar has been identified in soil organic carbon (SOC) mineralization, but the role of dissolved organic carbon (DOC) derived from biochar water extract (BE) is not well recognized. Therefore, rotary tillage (RT) and no-tillage (NT) with two moisturizers treatments; BE and distilled water (WA) were used to study the influence of DOC (through BE) on SOC mineralization and C fractions. Four soil sampling depths (0-10, 10-20, 20-30, 30-50 cm) were used for laboratory incubation. The results showed a significant increase in cumulative CO2-C emissions in upper soil that decreased with increase in soil depth. BE increased cumulative CO2-C emissions about 50% and 46% (0-10 cm), 45% and 26% (10-20 cm), 42% and 55% (20-30 cm), 16% and 43% (30-50 cm) than WA in NT and RT, respectively. Moreover, NT had 13% more cumulative CO2-C emissions than RT at 0-10 cm, but RT had 10% and 38% higher cumulative CO2-C emissions than NT at 10-20 and 20-30 cm soil depths, respectively. BE increased microbial quotient (Mq) almost 47%, 70%, 24% and 167% at 0-10, 10-20, 20-30 and 30-50 cm soil depths, respectively. Increase in Mq significantly decreased SOC and some carbon fractions. Notably, BE did not modify DOC in whole soil profile under both tillage systems. BE had significant higher MBC at 30-50 cm soil depth than WA in both tillage systems. RT had significant higher (4%) MBC than NT at 20-30 cm soil depth. Overall, addition of DOC from BE in soil enhances C mineralization by modifying Mq. (C) 2020 Elsevier B.V. All rights reserved.

Climate change is a global issue threatening agricultural production and human survival. However, agriculture sector is a major source of global greenhouse gases (GHGs), especially CH4 and N2O. Crop residue returning (RR) is an efficient practice to sequestrate soil carbon and increase crop yields. However, the efficiency of RR to mitigate climate change and maintain food security will be affected by the response of GHG emissions at both per area-scale and per yield-scale. Therefore, a national meta-analysis was conducted using 309 comparisons from 44 publications to assess the responses of GHG emissions to RR in China?s croplands. The results indicated that little response of GWP to RR was observed with conditions under lower nitrogen fertilizer input rates (0?120 kg ha-1), mulch retention, returning one time in double cropping systems, returning with half residue, weakly acidic soil (pH 5.5?6.5), initial SOC contents 20 g kg-1, or mean annual precipitation <1000 mm. In order to mitigate climate change and sustain food security, RR combined with paddy-upland rotation, nitrogen fertilizer input rates of 240?360 kg ha-1, and neutral soil (pH 6.5?7.5) could decrease GWP at per unit of crop yield, which ultimately leads to a lower effect on GHGI and a higher crop production efficiency. In-depth studies should be conducted in the future to explore the interactions between various factors influencing GHG emissions under RR conditions. Overall, optimizing the interactions with management and site-specific conditions, potential for regulating GHGs emissions of RR can be enhanced.

Tillage regimes play an important role in soil organic carbon (SOC) accumulation and atmospheric carbon mitigation. However, the mechanism of SOC decomposition induced by tillage regimes is not clearly understood, particularly related to SOC protection by soil iron (Fe) and aluminum (Al) oxides. Therefore, we assessed three types of soil Fe/Al oxides (Non-crystalline oxides, Feo/Alo; organic bound oxides, Fep/Alp; total free Fe/Al, Fed/Ald), and their relationship with SOC mineralization at the 0-50 cm soil depth after long-term tillage practices in a double rice cropping system in southern China. Four tillage practices were investigated: conservation tillage (no tillage + rice residue mulch, NTS), traditional tillage including rotary tillage (RTS), and plow tillage with or without rice residue incorporation (CTS and CT, respectively). The Feo and Fep/Alp had lower concentrations in deeper soil layers compared with the topsoil. At the 0-50 cm soil depth, the Feo content in the NTS treatment was 1.55 mg g(-1), which was 7.5%, 9.3%, and 14.3% higher than that under RTS, CTS, and CT (P < 0.05), respectively. Additionally, the Feo and Fep/Alp were correlated (P <0.05) with SOC content and SOC mineralization. At the 0?50 cm soil depth, CT decreased almost all soil Fe/Al oxides as compared with the three residue retaining treat-ments. Higher SOC content was found with the application of residue retention particularly under NTS and RTS, possibly due to SOC and Fe/Al oxides bonding/protection. Furthermore, we discovered a potential source of SOC loss induced by tillage operation (particularly plow tillage), which inverts the deep soil (5-20 cm) to the surface, as deep soil lacks protection from Fe/Al oxides and has significant SOC mineralizability. (C) 2021 Elsevier B.V. All rights reserved.