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Policy and market incentives are rapidly expanding to promote soil organic carbon (SOC) sequestration in global croplands. Evidence suggests that long-term increases in SOC can influence both crop yield and nitrogen (N) fertilizer requirements, with the potential to help address two important sustainability challenges. However, increases in SOC may also trigger higher soil nitrous oxide (N 2 O) emissions, which would represent an important tradeoff for climate change mitigation. We tested the hypothesis that long-term increases in SOC are associated with higher crop yields and fertilizer N use efficiency (NUE), but at the cost of higher N 2 O emissions. Wheat was grown in two soils (SOC low and SOC high) under three N fertilizer rates (0, 100, and 200 kg N ha−1) in a mesocosm experiment. Soils were obtained (0–25 cm) from a 22-yr field experiment on no-till and cover cropping in California. Results indicate that total biomass and grain yield were higher for SOC low than SOC high at 100 kg N ha−1 but not the other N levels. Crop N uptake was also 28% greater for SOC low at 200 kg N ha−1, resulting in higher overall NUE. Soil N 2 O emissions increased for SOC high by 25–112% compared to SOC low , likely due to long-term changes in labile C and N pools, microbial activity, and soil structure influencing porosity and gas diffusion. While there are well-documented crop and environmental benefits from enhancing SOC in agricultural soils, results from this study suggest that changes in soil N 2 O emissions should be considered to accurately determine net GHG emission reductions. • Soil N 2 O emissions increased 25–112% with long-term soil carbon sequestration • Crop yields were not higher with increased SOC • Crop nitrogen uptake and nitrogen use efficiency decreased with increased SOC • Elevated N 2 O emissions presented a tradeoff for net GHG emission reductions [ABSTRACT FROM AUTHOR]

There is increasing interest in perennial crops to build soil carbon (C), but the mechanisms underlying soil C accrual in perennial croplands remain unclear, especially over time in the first years of perennial crop growth. To address this gap, research is needed that directly tracks intra-annual C fluxes through crop-microbial-soil pools, evaluating the capacity of perennial crops to build soil C over intra-decadal time periods. We conducted a 13C isotope-tracer study to compare within-season C uptake and crop-microbial-soil C partitioning patterns between 1-year-old (IWG-1) and 2-year-old (IWG-2) stands of a novel perennial grain crop, intermediate wheatgrass (IWG; Thinopyrum intermedium (Host) Barkworth and Dewey). We compared these to a common annual grain crop, spring wheat (Triticum aestivum L.). Crop shoots, roots, soil, and soil respired-C were sampled ten times over a 90-day chase period. We also measured the incorporation of recently assimilated 13C into soil microbial biomass (13C PLFA) and functional groups over the first 7 days post-label application. Overall, IWG-1 assimilated almost 1670 mg 13C m−2 during the study period, nearly twice that of IWG-2 or wheat, but neither IWG system retained significant amounts of new C in soil. Rather, a higher proportion of assimilated new C was retained in IWG-1 in root tissues (14%) and arbuscular mycorrhizal fungi when compared to other cropping systems, while IWG-2 retained almost 50% of total assimilated C in aboveground crop tissues. We expect the shift from new C retention in belowground root-mycorrhizal networks to aboveground tissues is associated with a shift from an acquisitive to conservative growth strategy that occurs between the first and second IWG production years. The observed shift in C partitioning patterns and potential change in growth strategy limited the allocation and retention of new C in soil as IWG aged, adding valuable context to our understanding of why perennial grain crop establishment seldom leads to significant carbon gains in the first several years following establishment. • 13C-CO 2 labelling revealed age-related changes in perennial grain C partitioning • 1st-year perennial grain retained new C in roots, but little new C retained in soil • Sharp decline in new C uptake and belowground retention in 2nd-year perennial grain • Changes in primary microbial consumers of new C observed between 1st- and 2nd-year [ABSTRACT FROM AUTHOR]

Wheat plays a crucial role in Morocco's food security, economic stability, and livelihoods of farming communities. Assessing key vegetation indices (as yield predictors), along with understanding potential yield, yield gap, and major determinants for this gap at regional and national scales, is vital for improving food security with resilience in variable climatic conditions. Analysing the yield gap and its causes during drought and optimal weather conditions can reduce crop failure risks and enhance productivity specially in variable rainfed production systems. This study aimed to develop scalable methodology to predict field- and landscape-level yield and yield gaps for wheat and their underlying causes examplifying Morocco's rainfed production environment combining remote sensing, machine learning, and ground information. By analysing six vegetation indices (EVI2, CGVI, MSR, NDVI, OSAVI, and RVI) derived from Sentinel-2 satellite imagery (10 m resolution) over three successive growing seasons (2018–2019, 2019–2020, and 2020–2021), the study employed advanced vegetation index models for accurate prediction of wheat yields and yield gaps at plot and on a larger regional scale within the Rabat-Sale-Kenitra region. To identify the determinants of yield gap, climate and soil datasets were merged with crop management information and the random forest model was fine-tuned and assessed for each season and cumulatively. The findings highlighted that RVI, GCVI, and NDVI vegetation indices were particularly effective in predicting wheat yields, showing the highest R2 and the lowest prediction errors (RMSE). Such predictive methodologies are crucial for policymakers to proactively plan and mitigate risk minimization and adaption plans at regional and national levels. The models predicted rainfed potential yields of 5.99, 1.53, and 4.66 t ha−1, with corresponding yield gap of 3.38, 0.73, and 1.58 t ha−1 for the seasons of 2018/2019 (favorable); 2019/2020 (drought) and 2020/2021 (favorable), respectively. Across three periods, critical factors determining yield include soil moisture, total rainfall during the crop growing period, evapotranspiration, and soil texture and carbon content. To minimize drought risks and maximize benefits during variable rainfall conditions, it is essential to implement pre-season drought forecasts, customize seeding dates based on soil moisture, adopt technologies that enhance soil moisture retention, and utilize climate-adapted farming practices in the semi-arid and arid rainfed regions. • Predicting yield gap and determinants is essential for improving resilience. • RVI, GCVI, NDVI, OSAVI, and EVI2 are top indicators for wheat yield prediction. • Yield gap of wheat varies from 1.53 to 5.99 t ha−1 in rainfed areas. • Soil moisture, rainfall and crop management are yield determinants in rainfed area. • Drought forecasting and tailored agronomy based on soil moisture are imperative. [ABSTRACT FROM AUTHOR]

Soils with high organic carbon (SOC) have been shown to enhance crop yields while minimizing climate-induced losses. However, the resilience impacts and mechanisms by which high SOC enhances crop performance have not been fully explored. Here, eight-year rotations of winter wheat and summer maize managed with chemical fertilizer input alone (CF) or with cattle manure (OM) or with peat and vermiculite (PV) were conducted, and various soil properties were measured alongside crop growth, nitrogen (N) uptake, and grain yield, with seasons categorized as dry or normal based on precipitation amounts. The OM and PV treatments increased SOC by 57% and 78% relative to the CF, respectively, and improved soil nutrient availability and the soil quality index. Soil moisture content in the 0–30 cm layer increased by 3.5–26.6%, but was less influenced in the 30–90 cm soil layers. Annual yield of wheat plus maize increased by 13% and 12% in OM and PV compared to the CF, and the yield sustainability index increased by 29% and 17%. Yield gains were more pronounced in dry compared to normal seasons, ranging from 19% to 28% and 12–15% for wheat. At least in part, the relative advantages of OM and PV treatments under drying conditions were associated with accelerated growth and N uptake rate from sowing to stem elongation for wheat and maize. Among the factors influencing yield in the present study, soil moisture exerted the greatest positive total effect on yield. Overall, the results highlight that enhanced SOC resulting from combined application of organic amendments and mineral fertilizer was positively associated with yield by promoting soil quality and water availability, with a more pronounced benefit under water-limited conditions. [Display omitted] • Improved soil quality and moisture enhance wheat and maize yield and stability. • Combined inorganic fertilizer and organic amendments increased soil moisture in the 0–30 cm but not in deeper layers. • Better soils with high SOC enhanced wheat and maize yield and stability during dry seasons. • Accelerated vegetative growth and nutrient uptake by high SOC contributed to productivity resilience. [ABSTRACT FROM AUTHOR]

The introduction of novel perennial grains into annual row crop rotations is proposed to increase soil ecosystem services and enhance plant-soil-microbial linkages because perennials provide deeper root systems and more continuous ground cover than annuals. While soil microbial communities underpin many ecosystem services, we know little about how soil microbial composition and diversity, and soil carbon storage, differ between soils of annual vs. perennial grain crops. We measured soil fungi: bacteria (F/B) ratios and soil carbon within the novel perennial intermediate wheatgrass (IWG; trademarked Kernza®) and tilled annual wheat and compared soil microbial diversity and community composition within their rhizosphere, shallow bulk soil (0–15 cm) and total bulk soil (0–90 cm). After three years, soil depth explained 30–40% and 12–22% of the variance in bacterial and fungal community composition, respectively, while crop type explained 10% and 9–16% of the variance, respectively. Fungal communities were most impacted by crop type in the rhizosphere and shallow bulk soil and less sensitive to differences in soil depth. In contrast, crop type had a smaller effect on bacterial communities which were more influenced by soil depth. IWG trended higher in soil carbon mass at 0–30 cm (p = 0.22) and had a higher (F/B) ratio than tilled annual wheat at depths below 15 cm, but tilled annual wheat had higher soil carbon concentration (p = 0.12) and soil carbon mass (p = 0.09) at the 60–90 cm soil depth. Our results indicate that fungi were more responsive than bacterial communities to crop type and that IWG has a higher fungal biomass and different fungal community composition than annual wheat at depth. However, despite these distinct differences in fungal communities in IWG compared to annual wheat, the differences did not translate into greater soil carbon mass in IWG at depth. • Annual and perennial grains host different soil microbial communities. • Microbial community composition is influenced more by soil depth than crop type. • Annual vs. perennial influences are stronger in fungal than bacterial communities. • IWG increases carbon in the topsoil, annual wheat increases carbon in subsoil. [ABSTRACT FROM AUTHOR]

• Tillage timing did not affect macronutrient in the soil over time. • No-tillage was better in maintaining nutrients in soil over time. • No-tillage had lower grain N than Spring or Fall tillage. Tillage is known to significantly affect crop residue decomposition and soil nutrient dynamics, but the impacts of tillage on soil and plant macronutrients concentration with time have not been reported. This study was conducted (i) to assess the influence of tillage timing and intensity on soil and wheat (Triticum aestivum L.) macronutrient concentration of a winter wheat-dry pea (Pisum sativum L.) rotation (WW-P) under a dryland cropping system, and (ii) to compare macronutrients in the tillage treatments with a nearby long-term grass pasture (GP). The tillage treatments were fall tillage (FT), spring tillage (ST), no-tillage (NT) and disk/chisel tillage (DT/CT). Soil samples from 1995, 2005, and 2015 were analyzed to determine the concentration of soil organic carbon (SOC), total N and S, Mehlich III extractable P, K, Ca, and Mg, and soil pH. The impact of tillage on soil macronutrient concentration was evident after 52 years of WW-P. As a result, greater concentration of SOC, total S, and extractable P, and K were observed under NT than under FT or ST. The WW-P plots lost 28, 46, and 67% of SOC, Mg, and S, respectively, in the top 10 cm of soil compared with the GP plots, whereas the NT plots were the only plots in WW-P to maintain a P concentration (99 mg P kg−1) comparable with GP plots (102 mg P kg−1) at the same depth. The results indicated that NT could be beneficial to recharge the soil nutrient pool over time compared to FT or ST. [ABSTRACT FROM AUTHOR]

Abstract Crop residue is a source of energy and nutrients for microbial growth, and can be converted into soil organic matter (SOM). However, there are still knowledge gaps on how the interaction of crop residue and supplementary nutrients (nitrogen, phosphorus and sulfur) influence the fate of residue in microbial biomass carbon (MBC) and microbial use efficiency. Here, we quantified the carbon (C) mineralization of wheat residue (δ13C 494‰) and microbial C use efficiency at ecosystem scale (CUE E) with two levels of the residue (6.7 and 20.0 g kg−1 soil) and three levels of nutrients in Luvisol and Vertisol under a controlled laboratory condition (22 °C). Between 48 and 61% of residue-C was mineralized over 245 days. The residue CUE E was similar across the two levels of the residue on day 3 (i.e. , 0.29–0.40 in the Luvisol and 0.41–0.50 in the Vertisol) and then decreased over time, likely because of greater increase in cumulative total respiration and microbial turnover, relative to microbial growth. The residue CUE E was 20–55% lower in the high-residue, compared with (cf.) low-residue, input after day 10, which may have resulted from the greater loss of C via overflow respiration (microbial respiration without the production of energy) and turnover of high MBC. Narrowing of the C-nutrient imbalance increased residue-C mineralization, residue-derived MBC, and residue CUE E only under the high-residue input scenario where nutrients were possibly a limiting factor for microbial growth. Consequently, the results indicate a higher efficiency of SOM formation from returning of residue to soils under (i) low-residue (cf. high-residue) with or without nutrients, and (ii) high-residue with nutrient inputs (cf. no nutrient). The findings of the integrated residue–nutrient management on dynamics of residue-derived MBC and residue CUE E can be used to improve predictive performance of the models on specific soil functions such as SOM storage in agro-ecosystems. Graphical abstract Image 1 Highlights • Examined integrated wheat residue-nutrient management on C dynamics in two soils. • Residue-C mineralization & MBC greater in soils with high (cf. low) residue input. • Microbial C use efficiency (CUE) greater in soils with low (cf. high) residue input. • Nutrient input increased C mineralization and MBC only under the high-residue input. • Nutrient input increased microbial CUE initially only under the high-residue input. [ABSTRACT FROM AUTHOR]

Cadmium (Cd)-contamination of agricultural soils has been receiving attention worldwide due to its entry into food crops such as wheat ( Triticum aestivum L.). Little is known regarding the use of organic carbon (OC) sources in alleviating Cd toxicity in cereals. The current experiment was aimed to study the effects of different OC sources on the Cd accumulation by wheat. A pot study was conducted to determine the effects of rice husk biochar (RHB), farmyard manure (FYM), and lignite (LT) either alone or in combination on crop growth, Cd bioavailability and health risk assessment. The results proved that the application of OC sources like RHB, FYM, and LT either alone or in combination were highly effective in enhancing the wheat growth and yield as well as in minimizing the phyto-available fraction of Cd and its transfer to edible tissue of wheat. The RHB was the most efficient source in enhancing the plant growth and reducing the Cd concentration in wheat tissues. RHB increased grain yield by 91% and decreased Cd concentration in shoot, roots, grains, and bioavailable fraction of Cd by 67, 69, 62.5, and 74% than control, respectively. The RHB reduced the daily Cd uptake and health risk index in adults in comparison to control. Overall, where un-amended soil resulted in diminished plant productivity, the application of other OC sources also significantly proved their potential to enhance the dry weight and grain yield, suggesting that these OC sources may be used aiming to minimize the Cd concentration in crops. However, there is still a need to explore the potential of different OC sources in combination with other frequently available amendments for their large scale implementation in metal-contaminated soils. [ABSTRACT FROM AUTHOR]

This 2-year study aimed to verify whether the continuous application of no tillage (NT) for over 20 years, in comparison with conventional tillage (CT), affects nitrous oxide (N 2 O) and ammonia (NH 3 ) emissions from a Vertisol and, if so, whether such an effect varies with crop sequence (continuous wheat, WW and wheat after faba bean, FW). To shed light on the mechanisms involved in determining N-gas emissions, soil bulk density, water filled pore space (WFPS), some carbon (C) and nitrogen (N) pools, denitrifying enzyme activity (DEA), and nitrous oxide reductase gene abundance (nosZ gene) were also assessed at 0–15 and 15–30 cm soil depth. Tillage system had no significant effect on total NH 3 emissions. On average, total N 2 O emissions were higher under NT (2.45 kg N 2 O-N ha − 1 ) than CT (1.72 kg N 2 O-N ha − 1 ), being the differences between the two tillage systems greater in FW than WW. The higher N 2 O emissions in NT treatments were ascribed to the increased bulk density, WFPS, and extractable organic C under NT compared to CT, all factors that generally promote the production of N 2 O. Moreover, compared to CT, NT enhanced the potential DEA (114 vs 16 μg N kg − 1 h − 1 ) and nosZ gene abundance (116 vs 69 copy number mg − 1 dry soil) in the topsoil. Finally, NT compared to CT led to an average annual increase in C stock of 0.70 Mg C ha − 1 year − 1 . Though NT can increase the amount os soil organic matter so storing CO 2 into soil, some criticisms related to the increase of N 2 O emission arise, thereby suggesting the need for defining management strategies to mitigate such a negative effect. [ABSTRACT FROM AUTHOR]

Aggregate-size classes may have different microbial accessibility and therefore different decomposability of aggregate-associated soil organic matter (SOM). However, processes and mechanisms of soil organic carbon (SOC) mineralisation and availability of nutrients [nitrogen (N), phosphorus (P) and sulphur (S)] in different aggregate-size classes, and particularly, the interaction of aggregates with tillage intensity and crop residue type in contrasting soils is poorly understood. Soil samples from conventional tillage (CT) and reduced tillage (RT) systems under mixed wheat–pasture farming, and no-till (NT) under continuous cereal–cover cropping in a Luvisol, and from CT and NT under continuous wheat cropping in a Vertisol, were separated into three dry aggregate classes of different sizes [mega-aggregates (>2–6.5 mm), macro-aggregates (0.25–2 mm) and micro-aggregates (<0.25 mm)]. Two residue types (canola and wheat stem; δ 13 C 124 and 460‰, respectively) were added into each of the three aggregate class samples from Luvisol (δ 13 C −24.7‰) and Vertisol (δ 13 C −18.5‰). Total CO 2 -C, δ 13 C in CO 2 -C, microbial biomass C (MBC), and plant available N, P and S were measured periodically during the 126-day incubation. The results showed that crop residue input increased native SOC mineralisation ( via positive priming), MBC and microbial metabolic quotient in all three aggregate-size classes from different tillage systems in both soils. Native SOC mineralisation was 1.5–3.7 and 0.6–2.8 times higher in the canola and wheat residue-amended ( cf . control, non-amended) aggregates, respectively. Native SOC mineralisatiion and MBC were higher in the macro- and micro- than mega-aggregates in both soils. However, priming of native SOC mineralisation, relative to the control, was similar across the aggregates, except for the CT in the Luvisol where priming was higher in the macro- than micro- and mega-aggregates. Native SOC mineralisation among the aggregate-size classes was 26–114% higher under CT or RT cf . NT in the Luvisol but was similar under CT and NT in the Vertisol. Net available N was significantly higher in the residue-amended than the control aggregates, particularly in the CT and/or RT versus the NT at day 30 only, and mainly in the Luvisol. Further, substantial amounts of available P and S were released from the residue-amended versus the control aggregates at day 126, with Vertisol releasing 2–3 times more available P than Luvisol. In conclusion, our findings showed the importance of returning crop residues to enhance nutrient availability from all aggregate-size classes in different soils and farming systems. In particular, the tillage ( versus no-till) and canola ( versus wheat) residue induced a greater release of nutrients, generally in the pattern of micro- ≥ macro- > mega-aggregates. Clearly, the input of crop residues enhanced the release of SOM-bound nutrients, possibly via positive priming, and may have mobilised mineral-bound nutrients, such as P and S in each aggregate-size class, with tillage intensity and soil type modulating these processes. [ABSTRACT FROM AUTHOR]

The effect of integrated nutrient management practices on soil organic carbon (SOC) fractions, soil carbon (C) storage and grain productivity was investigated in winter wheat (Triticum aestivum) for two consecutive seasons (2013–2015). Fertility treatments were NPK as recommended inorganic fertilizer, NPK + cowdung, NPK + whole parts of the green manure plant Sesbenia aculeata , NPK + compost of Azolla caroliniana and NPK + rice husk dust. Application of NPK through inorganic fertilizer and in combination with organic amendments increased SOC and its active (microbial biomass C and dissolved organic C) and passive carbon fractions (humic and fulvic C, recalcitrant C). Application of organics with inorganic fertilizers resulted in greater soil C accumulation over inorganic fertilizer alone. Greater proportion (46%) of oxidizable organic C in the less labile fraction (F3) and recalcitrant fraction (F4) were found in the soil due to NPK + Azolla compost application. Higher concentration of microbial biomass C (MBC) was recorded at NPK + cowdung and NPK + Sesbenia aculeata . The trends in dissolved organic C (DOC) are similar to trends with the soil labile C pool (F1 and F2). Principal component analysis (PCA) demonstrated a close association among the recalcitrant C fraction, humic and fulvic C and the degree of humification of SOC. These fractions were apparently transformed more slowly in the soil and persisted for longer when Azolla compost was added. Azolla compost application with inorganic fertilizer (NPK) may therefore be a good strategy for reducing carbon dioxide (CO 2 ) in the atmosphere through increased flag leaf photosynthesis and by formation of stable humified substances in the soil without compromising the grain productivity. The amendments significantly increased the photosynthetic rate of wheat in reproductive growth stage. Grain yield was increased 27% due to NPK + Azolla compost application compared to control (NPK). The inorganic and organic amendments tested in this study enhanced soil C storage and plant C fixation in a continuous winter-wheat cropping system in India. [ABSTRACT FROM AUTHOR]

Organic reduced tillage aims to combine the environmental benefits of organic farming and conservation tillage to increase sustainability and soil quality. In temperate climates, there is currently no knowledge about its impact on greenhouse gas emissions and only little information about soil organic carbon (SOC) stocks in these management systems. We therefore monitored nitrous oxide (N 2 O) and methane (CH 4 ) fluxes besides SOC stocks for two years in a grass-clover ley – winter wheat – cover crop sequence. The monitoring was undertaken in an organically managed long-term tillage trial on a clay rich soil in Switzerland. Reduced tillage (RT) was compared with ploughing (conventional tillage, CT) in interaction with two fertilisation systems, cattle slurry alone (SL) versus cattle manure compost and slurry (MC). Median N 2 O and CH 4 flux rates were 13 μg N 2 O-N m −2 h −1 and −2 μg CH 4 C m −2 h −1 , respectively, with no treatment effects. N 2 O fluxes correlated positively with nitrate contents, soil temperature, water filled pore space and dissolved organic carbon and negatively with ammonium contents in soil. Pulse emissions after tillage operations and slurry application dominated cumulative gas emissions. N 2 O emissions after tillage operations correlated with SOC contents and collinearly to microbial biomass. There was no tillage system impact on cumulative N 2 O emissions in the grass-clover (0.8–0.9 kg N 2 O-N ha −1 , 369 days) and winter wheat (2.1–3.0 kg N 2 O-N ha −1 , 296 days) cropping seasons, with a tendency towards higher emissions in MC than SL in winter wheat. Including a tillage induced peak after wheat harvest, a full two year data set showed increased cumulative N 2 O emissions in RT than CT and in MC than SL. There was no clear treatment influence on cumulative CH 4 uptake. Topsoil SOC accumulation (0–0.1 m) was still ongoing. SOC stocks were more stratified in RT than CT and in MC than SL. Total SOC stocks (0–0.5 m) were higher in RT than CT in SL and similar in MC. Maximum relative SOC stock difference accounted for +8.1 Mg C ha −1 in RT-MC compared to CT-SL after 13 years which dominated over the relative increase in greenhouse gas emissions. Under these site conditions, organic reduced tillage and manure compost application seems to be a viable greenhouse gas mitigation strategy as long as SOC is sequestered. [ABSTRACT FROM AUTHOR]

[Display omitted] • OFS increased wheat yield and soil quality in two soils. • ROC, KOC, HKOC, and MKOC were the key fractions affecting SOC. • OFS increased SOC content by regulating KOCs transformation in two soils. • HKOC and MKOC can monitor and evaluate SOC and soil C pool changes. Organic fertilizer substitution (OFS) technology effectively mitigates the adverse effects of excessive synthetic fertilizer application while promoting soil organic carbon (SOC) sequestration in farmlands. However, how the permanganate oxidizable carbon fractions (KOCs) transformation affects SOC under OFS remains unknown. In this study, two typical farmland soils (grey desert soil, GS; meadow soil, MS) were selected for a 3-year field fertilization experiment (no fertilization, NF; synthetic fertilizer alone, SCF; and organic fertilizer substituted 20% synthetic N fertilizer, OFS). Field experiments conducted from 2018 to 2020 showed that SOC could be used to evaluate wheat yield and soil quality, so further study the effects of OFS on SOC and KOCs and their corresponding C pool management index (CPMIs). The results showed that OFS in GS and MS increased SOC (by 3.37%–15.62%, 4.92%–20.28%) and its fractions content (except low-activity KOC, LKOC) and CPMIs (except CPMI-L) year by year compared to SCF and NF. The recalcitrant organic C (ROC), KOC, high-activity KOC (HKOC), and medium-activity KOC (MKOC) were the key fractions affecting SOC. Moreover, HKOC and MKOC and their corresponding CPMIs (CPMI-H and CPMI-M) showed higher sensitivity. Structural equation modeling revealed that OFS in GS and MS increased SOC by increasing ROC and KOC (by regulating KOCs transformation) content, and increased CPMI-H and CPMI-M by increasing HKOC and MKOC content. Overall, the process of OFS promoted SOC sequestration and improved soil C pool in two soils were revealed from the perspective of KOCs transformation. Also, we proposed corresponding fertilization recommendations and showed that HKOC and MKOC could be used to evaluate and monitor soil quality and SOC. This study provides guidance for SOC sequestration, crop yield, and soil quality improvement in oasis wheat fields, contributing to the sustainable development of farmland. [ABSTRACT FROM AUTHOR]

Summer fallow – the practice of keeping a field out of production during the growing season – is a common practice in dryland wheat ( Triticum aestivum L.) cropping systems to conserve soil water resources. Fallow also depletes soil carbon stocks and thereby soil quality. The area of summer fallow has decreased by tens of millions of hectares since the 1970s in the northern North American Great Plains as producers have recognized that avoiding fallow usually confers both economic and soil conservation benefits. Observed summertime cooling across parts of this region has coincided with fallow reduction, suggesting that the role of fallow in atmospheric processes needs to be ascertained. We measured carbon dioxide, latent heat, and sensible heat flux across a winter wheat – spring wheat – fallow sequence in Montana, USA to determine the effects of dryland crop management on ecosystem carbon resources and energy partitioning at the surface-atmosphere interface. Winter wheat and spring wheat fields were carbon sinks ( F c = −203 ± 52 g C CO 2 m −2 and −107 ± 29 g C CO 2 m −2 ), respectively, during the April to September study period, but the fallow field was a carbon source of 135 ± 73 g C CO 2 m −2 . Evapotranspiration in the wheat crops was over 100 mm greater than the 275 ± 39 mm observed in the fallow field during the study period. Modeled maximum daily atmospheric boundary layer height was on average 210 m higher and up to 900 m higher in fallow compared to the spring wheat field with more crossings of the modeled atmospheric boundary layer and lifted condensation level, suggesting that regional studies of the effects of fallow on near-surface temperature and moisture are necessary to understand the effects of fallow reduction on regional climate dynamics. Results demonstrate that fallow has a detrimental impact to soil carbon resources yet is less water intensive, with consequences for regional climate via its impacts on atmospheric boundary layer development and global climate via its carbon metabolism. [ABSTRACT FROM AUTHOR]

Diversification of conventional food-based cropping system with multipurpose lignocellulosic crops could increase biodiversity, farmer's market opportunities, feedstock for biorefineries, though can also imply soil organic carbon (SOC) stock changes, without competing with food production. Sunnhemp (Crotalaria juncea L.), biomass sorghum (Sorghum bicolor L.), kenaf (Hibiscus cannabinus L.), and industrial hemp (Cannabis sativa L.) are annual high yielding lignocellulosic crops with great potential for their multiple applications. The objective of the present study was to identify the SOC changes when the aforementioned crops are grown during the fallow periods of a conventional maize (Zea mays L.)-wheat (Triticum aestivum L.) rotation over five years. For this purpose, the SOC, carbon inputs (i.e. above and belowground residues), soil respiration, and cumulative CO 2 emissions were evaluated. The experiment was carried out in northern Italy (44°30′ N, 11°21′ E) from 2016 to 2021 in a randomized complete block design (n = 4) by adopting conventional field and harvest management practices (i.e. straw removal with hay machineries and alternating conventional with minimum tillage). The SOC stock increased by 7% from 2016 (56 Mg ha−1) to 2021 (60 Mg ha−1), regardless of the rotation system. Despite one of the highest CO 2 cumulative soil emissions (11 Mg ha−1 , two and three times higher than sunnhemp, kenaf, and industrial hemp, respectively) the rotation including biomass sorghum ended with higher SOC concentration (7.6 g kg−1) compared with industrial hemp (7 g kg−1) and kenaf (6.9 g kg−1), whereas fallow (7.2 g kg−1) and sunnhemp (7.1 g kg−1) showed intermediate values. The combination of high aboveground residues and high nitrogen fertilizations are deemed to act primarily on SOC level compared with belowground residues. In summary, the crop intensification did not deplete SOC, moreover biomass sorghum cropping system outperformed kenaf and industrial hemp through the decomposition into SOC of higher released residues. The rotation including sunnhemp coupled high SOC levels with low CO 2 emissions, raising interest in the light of its nitrogen fixing ability which can further help reducing the system's carbon footprint. • Cropping systems with wheat and maize including lignocellulosic crops during the fallow period are presented. • Over five years, the SOC carbon stock increased by 7%, regardless of rotation. • The rotation resulting with the highest SOC concentration included biomass sorghum (7.6 g kg−1). • The rotation resulting with the lowest SOC concentration included industrial hemp (7 g kg−1), and kenaf (6.9 g kg−1). • Aboveground crop residues, reduced tillage and nitrogen fertilization are likely the main drivers influencing SOC. [ABSTRACT FROM AUTHOR]

Quantifying changes in soil organic carbon (SOC) is essential for understanding the effect of managements on carbon (C) sequestration, especially in cultivated marginal lands. The objectives of this study were to determine the short- (<3 yr) and long-term (>24 yr) effects of a one-time compost application on soil organic matter (SOM) pools and stocks: coarse particulate organic matter (cPOM), fine particulate organic matter (fPOM), mineral-associated organic matter (MAOM), and soil physical quality (SOC:clay ratio) in surface- and sub-soils. Manure compost (0, 25, and 50 Mg dry weight ha–1) was applied to three organic dryland winter wheat-fallow systems (WW-F): Historic, (HT, >24 yr), Snowville (SN, < 3 yr), and Blue Creek (BC, <3 yr), in northern Utah. At HT, cPOM-C concentrations in amended plots were higher than under the control plots at the 0–10- (84.6 vs 54.4 g OC kg-1 fraction) and 10–30-cm (34.4 vs 19.4 g OC kg-1 fraction) depth. Compared to control plots, compost increased MAOM-C concentration from 1.8 to 3.4 g OC kg-1 fraction at the 30–60-cm at SN and from 2.35 to 3.99 g OC kg-1 fraction at the 60–90-cm depth at BC. Similarly, cPOM-C concentration was also increased at SN (5.5–23.6 g OC kg-1 fraction, 30–60-cm) and BC (8.3–31.2 g OC kg-1 fraction, 60–90-cm). The SOC:clay ratio was significantly higher at the 30–60-cm depth at BC (1:50–1:40) and at the 60–90-cm depth at SN (1:70–1:30), which suggests that compost application can impact subsoil physical quality. Thus, one-time compost application at 16.5 Mg C ha-1 every two decades might constitute a reasonable management option for managing C in dryland WW-F agroecosystems. • Effect of a one-time compost application on particulate organic matter is detectable 24 years later. • A one-time compost application moderately improves subsoil organic carbon. • Application of compost can enhance subsoil quality in non-irrigated dryland soils. [ABSTRACT FROM AUTHOR]

Changes in field management and climate will alter soil organic carbon (SOC) and nitrogen (SN) cycling in the coming decades. This study is to quantify the effects of various fertilisation strategies and climate change scenarios on crop yield, and soil C and N cycling by the end of this century. Data from a long-term experiment with a winter-wheat ( Triticum aestivium L.) and summer maize ( Zea mays L.) rotation in Northern China was used to calibrate and validate the SPACSYS model. Five fertiliser practices were used: control (CK); combined mineral nitrogen, phosphorus and potassium (NPK); NPK plus manure (NPKM); high application rate of NPK fertilisers plus manure (hNPKM) and NPK with straw incorporation (NPKS). Crop yields, and SOC and SN stocks by 2100 were predicted under four climate scenarios (Baseline, RCP2.6, RCP4.5 and RCP4.5). Results showed that the SPACSYS model can adequately simulate the dynamics of SOC and SN stocks and the yields of winter wheat and summer maize. An application of NPK plus manure or straw not only enhanced crop yield, but also substantially increased SOC and SN stocks. The predictions showed the positive effects of fertilisation and climate change on crop yields and SOC stocks compared with those under the baseline. However, SN stock under the RCP8.5 decreased by 3–14% by 2100 for various fertilisation strategies compared with that under the baseline. On the other hand, mineral fertiliser plus manure led to a higher soil respiration rate and nitrogen losses through leaching and surface runoff under all the climate scenarios. Therefore, application of mineral fertilisers plus manure could enhance crop productivity and sustain soil fertility but cause more carbon emitted to the atmosphere and nitrogen losses. More attention should be paid on optimising fertilisation in order to increase crop productivity while minimising environmental risks. [ABSTRACT FROM AUTHOR]

The carbon management index (CMI) and labile organic carbon (LOC) pools are postulated as very sensitive indicators of changes in soil organic carbon (SOC) due to land degradation within a short time in response to management practices. To test this hypothesis, we investigated LOC and CMI under a field experiment (2007–2013) in relation to runoff, soil loss, maize and wheat yields on a 2% (1.15°) land slope of the Indian Himalayas. In this study, the impacts of several resource conservation practices, including different combinations of vegetative barriers (VB), minimum tillage (MT), different organic amendments (OA) and weed mulch, were evaluated. Results revealed that the plots under MT + OA with three applications of weed mulch had more SOC, macroaggregate-associated C concentrations and macroaggregates than conventional tillage (CT) + NPK with chemical weed control. Carbon management index varied from 47 to 59 and 42 to 55% with different conservation practices at depths of 0–5 and 5–15 cm depths, respectively. Incorporation of weed mulch along with application of OM, MT and VB (by Palmarosa ) under MT improved CMI by 19.7 and 24.2% compared to CT plots with VB (by Panicum ) and inorganic NPK at depths of 0–5 and 5–15 cm, respectively. Significant positive correlations were observed between CMI and maize yield ( r = 0.948; n = 24; P < 0.01), CMI and wheat yield ( r = 0.872; n = 24; P < 0.01) and CMI and wheat equivalent yield ( r = 0.906; n = 24; P < 0.01). However, significant negative correlations were obtained for CMI and runoff ( r = −0.701; n = 20; P < 0.01) and CMI and soil loss ( r = −0.768; n = 20; P < 0.01). Results established that Palmarosa as VB along with OA plus weed-mulch under MT was the best management practice for decreasing runoff and soil loss and increasing system productivity on a 2% slope in the region. The single value CMI was strongly positively correlated with crop productivity and negatively correlated with soil loss. Hence, this single value CMI could potentially be used for assessment of soil degradation elsewhere. [ABSTRACT FROM AUTHOR]

The aim of the study is to analyze the effects of different fertilization of organic and inorganic fertilizers on soil organic carbon (SOC) sequestration and crop yields after a 22 years long-term field experiment. The crop yields and SOC were investigated from 1981 to 2003 in Dry-Land Farming Research Institute of Hebei Academy of Agricultural and Forestry Sciences, Hebei Province, China. The dominant cropping systems are winter wheat–summer corn rotation. There were totally sixteen treatments applied to both wheat and corn seasons: inorganic fertilizers as main plots and corn stalks as subplots and the main plots and subplots all have four levels. The results revealed: after 22 years, mixed application of inorganic fertilizers and crop residuals, the SOC and crop yields substantially increased. Higher fertilizer application rates resulted in greater crop yields improvement. In 2002–2003, wheat and corn for the highest fertilizer inputs had the highest yield level, 6400 kg ha −1 and 8600 kg ha −1 , respectively. However, the SOC decreased as the excessive inorganic fertilizer input and increased with the rising application of corn stalks. The treatment of the second-highest inorganic fertilizer and the highest corn stalks had the highest SOC concentration (8.64 g C kg −1 ). Pearson correlation analysis shows that corn and winter wheat yields and the mineralization amount of SOC have significant correlation with SOC at p < 0.05 level. [ABSTRACT FROM AUTHOR]

[Display omitted] • Straw-derived biochar incorporation (BI) was compared to the straw mulching (SM) and straw incorporation (SI) on the Loess Plateau. • The BI treatment significantly increased soil water storage and grain yield compared to the SM and SI treatments. • Enhanced soil C and N content with the BI are closely related to changes in grain yield. • The BI significantly improved soil enzyme activities at jointing stage. • The BI could be a win–win practice to improve crop yield and soil fertility. The responses of yield production and soil nutrients availability to agricultural organic inputs are crucial for cropland management. However, the simultaneous impacts of straw-derived biochar and straw addition on yield production and soil properties (e.g., soil enzyme activities at winter wheat growing stages) as well as their potential relationships remain poorly evaluated in semi-arid areas. Here, a field experiment based on the long-term study (i.e., commenced in 2011) was conducted in the semi-arid Chinese Loess Plateau to explore the responses of soil water storage (SWS), winter wheat (Triticum aestivum L.) yield and a range of soil biochemical properties to straw-derived biochar and straw addition in 2018–2019 and 2019–2020. The four treatments were: 1) no straw and no biochar (Control), 2) conventional straw mulching (SM), 3) straw incorporated into the soil (SI), and 4) straw-derived biochar incorporated into the soil (BI). We found that the BI treatment on average increased SWS in 0–160 cm soil depth by 13%, 17%, and 21% across entire growing seasons, respectively, when compared to the SM, SI and Control treatments. Enhancements in grain yield and aboveground biomass were related to the BI treatment-induced increases in soil carbon and nitrogen content. The BI treatment had higher soil enzyme activities at jointing stage than at grain filling and maturity stages during winter wheat growing seasons. The mixed-effects models showed there were significant effects of growth stage and soil depth on soil microbial biomass and soil dissolved organic carbon and nitrogen, even when analyzed by each growing season. Moreover, no significant relationships were found between SWS and soil enzyme activities (invertase, urease, catalase, and alkaline phosphatase). Therefore, straw-derived biochar incorporation could be one of the appropriate practices for increasing crop yield and sustaining soil fertility in the Chinese Loess Plateau and other areas with similar climates. [ABSTRACT FROM AUTHOR]

Understanding the impact of soil degradation on crop productivity is essential for decision-makers to predict agronomic, economic, and environmental outcomes of agricultural operations. Soil organic carbon (SOC) is influenced by the cropping system and affects soil health through its effect on other soil physical, chemical, and biological properties. Data from a 56-year long-term experiment in Uruguay's Pampa region were analyzed to quantify the effects of soil degradation on wheat (Triticum aestivum L.), and barley (Hordeum vulgare) yields. A significant degree of soil degradation was generated by six rotations with variable annual crop and pasture proportions (0%, 33%, 50%, and 66% of non harvest pasture). Yield records (n = 368) and annual values of 14 explanatory variables containing soil, climatic, and management indicators were evaluated using random forest regressions. Rotation-induced SOC variation ranged from 1.2% to 2.6%, and robust relationships between SOC, soil physical, chemical, and biological properties were established. Over time, yields increased in crop pasture systems but plateaued for the annualized crop rotation (0% pasture). Yield improvements due to agronomic technology advances partly mask soil degradation effects. SOC losses lead to a reduction in yield, even when the SOC level was above 2%. Thus, no critical level of SOC could be determined. SOC interacted with climate indicators to impact yield. This analysis confirms the central role of SOC in yield outcomes beyond nutrient availability, and its potential to represent a wide range of soil functions. Our findings indicate that crop rotations with a higher percentage annual vs. perennial crops negatively impact SOC, associated soil properties, and yield potential. • SOC is a crucial indicator that summarizes a broader assessment of soil quality. • yield reductions associated with SOC losses represented 28% of average yields achieved. • impacts of SOC depletions were more pronounced under favorable weather conditions. [ABSTRACT FROM AUTHOR]

Different integrated crop management (ICM) modules have been developed to enhance the productivity and profitability of the rice-wheat rotation (RWR) of the upper Indo-Gangetic Plains (IGPs). As the available options are used quite often singly or with the few combinations, hence in the present study, eight ICM modules have been evaluated; wherein, ICM 1&2 - conventional transplanted rice fb flatbed wheat, ICM 3&4 - conventional direct seeded rice (DSR) fb furrow irrigated raised bed wheat without residues, ICM 5&6 - conservation agriculture (CA)-based modules [zero tilled (ZT) DSR and ZT wheat] with the wheat and rice residues, and ICM 7&8- CA-based modules (ZTDSR and ZT wheat) with the wheat, mungbean and rice residues. Results revealed that ICM 8 produced the highest mean rice grain yield, which was statistically similar to ICM 1&7 , however it was 10.1–20.7% greater than the ICM 2–6 modules. Similarly, the ICM 7 recorded 14–16% greater wheat grain yield than the ICM 1–6 (five years' mean), but it was at par to the ICM 8. Furthermore, the ICM 7&8 produced 10–13% (5 years av.) higher system yields in terms of rice equivalents over the ICM 1&2. Water use (WU) was the highest in ICM 1&2 and was 8–12% higher than the ICM 3–8. In contrast, the highest water productivity (WP) was recorded with the ICM 7&8 , wherein it was14–16% greater than the ICM 1&2. The ICM 1&2 had incurred the highest variable production costs (US$ 912–1105 ha−1 yr−1), followed by ICM 7&8 (US$ 856–1021 ha−1 yr−1). Nevertheless, on an average, the ICM 7&8 gave 19–22% additional returns than the ICM 1&2. Also, the ICM modules had a significant (p < 0.05) and positive impact on the soil carbon (0.0–0.45 m). The CA-based (ICM 5–8) residue retained modules registered a 10–25% greater total OC stock than the ICM 1–4 in 0.0–0.45 m soil layer. The current study thus up-holds the importance of adequate inputs integration, and hence, adoption of the CA-based ICM in the RWR improved the soil carbon dynamics, crop yields, farm profits, besides water savings of the upper Indo-Gangetic Plains (IGPs) of north-west India. • ZTDSR-ZT wheat (ICM 7&8) had a positive impact on the system yields (10–13%) and farm economics (19–22%) than CT modules (ICM 1&2). • Residue retained ZTDSR-ZT wheat (ICM 5–8) contributed 12–17% greater total OC stock than the CT practices (ICM 1–4). • Modules ICM 5–8 saved 8–12% water and increased the system water productivity by14-16% than the CT rice and wheat (ICM 1&2). • Synergistic effects of ICM components reflected in complimenting the supply of nutrients besides conserving soil fertility. [ABSTRACT FROM AUTHOR]

• 75% N in NT and CT increased SOC and STN compared to 100% N. • Soil quality, wheat and maize yields can be maintained by 75% N fertilizer. • The yield stability of the maize is greater than that of wheat. • CT increased yield stability and SOCS in 0–40 cm compared to NT. • NT increased STN concentration, STNS and NSR in 0–20 cm compared to CT. Excessive nitrogen (N) fertilizer application can cause resource waste and environmental pollution. Thus, whether the rate of N applied can be decreased under no-tillage, which usually increases soil carbon (C) and N stocks, has become an important topic. We hypothesized that a certain extent of N fertilizer application decrease under no-tillage can still maintain higher soil C and N stocks and yields of wheat and maize, however, the effects under different tillage systems may be different. To find the appropriate N fertilizer applications and tillage methods to keep higher soil C and N and crops yields, 10 treatments, including 2 tillage patterns (conventional tillage: CT and no-tillage: NT) and 5 fertilization rates (100%, 75%, 50%, 25% and 0 N of the common N fertilizer application), were tested in triplicate via a randomized block design on a Hapli-Udic Argosol during 2006–2016. The annual wheat and maize yields of 100% N, 75% N and 50% N under CT and NT treatments were significantly higher than those of 25% and 0 N on the studied period (P < 0.05). Higher yield stability of the wheat and maize were found under 75% and 50% N application compared to other N rates. However, the yield stability of wheat was lower than that of maize. The SOC concentration, SOCS and CSR of 75% N application were increased by 1.5, 2.2 and 20.6% than those of 100% N application respectively, in the 0–40 cm soil depth. The STN concentrations of NT-100 and NT-75 were significantly higher than those of other treatments (P < 0.05). The STNS and NSR in the NT-100 treatment were significantly higher than those of other treatments (P < 0.05). NT could lead to more accumulation of SOC and STN in the surface soil depth (0–20 cm) during 2007–2016. In conclusion, 75% of the common N application rate under NT and CT were better choices for sustainable agricultural development. [ABSTRACT FROM AUTHOR]