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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]

Abstract: Phosphate-solubilizing bacteria (PSBs) Pantoea cypripedii (PSB-3) and Pseudomonas plecoglossicida (PSB-5) isolated from organic field were studied for improvement of maize and wheat crop at multilocational sites with and without rock phosphate (RP) fertilization during two year of field study under different agroclimatic regions. Application of both the bacterial strains as bio-inoculants showed significant effect on maize and wheat grain yield and on soil fertility at all different agroclimatic regions. Grain yield, phosphorous (P) uptake, soil organic carbon, available P, enzyme activities and P-solubilizing bacterial population in all the experimental crop fields at different sites significantly increased due to inoculation. Improvement in crop yield and soil fertility at three different sites was more pronounced and significant when RP was supplemented along with seed inoculation compared to uninoculated control treatment. Present study results suggest that P. cypripedii (PSB-3) and P. plecoglossicida (PSB-5) along with RP fertilization play an important role in plant growth promotion and improvement of soil fertility in different agroclimatic regions. [Copyright &y& Elsevier]

Attention to farm management practices that enhance soil organic carbon (SOC) stock is increasing because of the latter's importance of soil fertility, crop production and the global carbon cycle. Sequestering atmospheric carbon dioxide (CO2) as SOC has potential feedback to climate change. Spatial modelling of the effects of wheat stubble incorporation by tillage on SOC storage was studied in a semi-arid rainfed wheat cropping system, using the Agricultural Production Systems Simulator (APSIM). The model was validated against a long-term (1979–2004) experiment and yielded a Ratio of Performance to Deviation (RPD) of 1.6 and R2 of 0.63, indicating a moderate accuracy in predicting SOC turnover. In the Liverpool Plains and the southern slopes of NSW, SOC at top 30cm layer is in a higher range of 40–50tha−1, while from the southern west plains to the northern plains extending to the New England tablelands, SOC is in a lower range of 25–35tha−1. It is notable that SOC in the central slopes is also in the lower range of 25–35tha−1. There is large simulated variation to changes in SOC from stubble management under the current climate that ranges from 0 to –200kgha−1 year−1 when 100% of the wheat stubble is removed. When 100% of the wheat stubble is 100% incorporated, the changes in SOC become positive, from 0 to 200kgha−1 year−1. The SOC change patterns associated with the rates of wheat stubble incorporation are similar under a projected future climate. However, as future temperatures rise, less SOC will be sequestered. For example, under the 100% removal of wheat stubble, the averaged SOC is decreased by 126±40kgha−1 yr−1 under the current climate, while under the 18 GCM projected climate (2049–2098), the reduction is 135±15kgha−1 yr−1. In contrast, when 100% wheat stubble is incorporated into the soil, the averaged SOC is increased by 100±34kgha−1 yr−1 under the current climate, while under the 18 GCM projected climate, the averaged SOC is increased by 80±23kgha−1 yr−1. To maintain the current level of SOC in the south-western wheat growing region (lower rainfall) of the state 20–40% wheat stubble is required to be incorporated into soil, compared to that in the north-eastern area (high rainfall), where the rate is about 40–60%. Across the actual wheat growing area in NSW, the decreased SOC with the 100% removal of wheat stubble results in 3.90±1.23Mt CO2 emissions per year under the current climate. Under the 18 GCM projected climate, the mean emission per year is 4.06±0.50Mt CO2 if 100% wheat stubble is removed from field. In contrast, when 100% wheat stubble is incorporated into soil, the amount of increased SOC will reduce the atmospheric CO2 emissions by 3.29±1.11Mtyr−1 under the current climate or by the mean of 2.68±0.77Mtyr−1 under the GCM projected climate. There is a clear trend to theoretically decrease CO2 emissions with the increased incorporation of wheat stubble. [ABSTRACT FROM AUTHOR]

Highlights: [•] Tilled wheat-fallow practices had less SOC stock at 0–30cm depth (∼10Mgha−1). [•] No-till wheat-fallow had more SOC at 0–30cm, but not in whole profile (0–120cm). [•] CRP grass–alfalfa mixture had more SOC at 0–30 and whole profile than tilled wheat-fallow. [•] However, soil inorganic C ranged from 8.1 to 24.9Mg/ha and was greatest under wheat-fallow practices. [•] CRP grass–alfalfa mixture has greater potential for SOC storage and to improve soil quality. [ABSTRACT FROM AUTHOR]

Highlights: [•] Conventional tillage left negative carbon footprint. [•] CH4 was largest contribution to carbon footprint. [•] Continuous no tillage was highest yielding practice. [•] Discontinuous tillage practice was worst environmental performer. [ABSTRACT FROM AUTHOR]

Highlights: [•] Wheat yield and water use increased with increase in irrigations. [•] Rice straw mulching decreased surface soil temperature and weed dry matter. [•] Mulching increased the water use efficiency, yield attributes and yield in wheat. [•] Highest water use efficiency recorded with 2 irrigations applied with 6tha−1 mulch. [•] Mulching decreased soil bulk density and increased organic carbon in surface soil. [ABSTRACT FROM AUTHOR]

Abstract: Agricultural soil is a potential sink for atmospheric carbon as soil organic carbon. The carbon sequestration is affected by cropping system and management practices adopted. Rice–wheat is a dominant cropping system in the Indo-Gangetic plains. Previous studies done by different research workers revealed both its positive as well as negative impacts on carbon sequestration. The objective of this study was to determine C sequestration after nine year''s rice (Oryza sativa L.)–wheat (Triticum aestivum L.) cropping under an ongoing experiment at Punjab Agricultural University, Ludhiana, Punjab (India). This study was based on five treatments (100%N, 100%NP, 100%NPK, 100%NPK+FYM and the control). In the surface soil layer (0–15cm), soil organic carbon (SOC) increased from the initial status of 2.42 to 3.26gkg−1 in the control, which significantly increased with the application of 100%NPK (4.11gkg−1) and 100%NPK+FYM (4.55gkg−1). The rice–wheat cropping even without any fertilization (control) contributed toward carbon sequestration (1.94MgCha−1) with soil organic carbon pools and carbon sequestration rate of 7.84MgCha−1 and 0.22MgCha−1 yr−1, respectively. The soil organic carbon pools, carbon sequestration and rate of carbon sequestration as observed in treatment of balanced fertilization (100%NPK) were significantly increased from 9.19 to 9.99MgCha−1, 3.30 to 4.10MgCha−1 and 0.37 to 0.46MgCha−1 yr−1, respectively when farmyard manure was applied in conjunction with 100%NPK. The application of 100%NPK and 100%NPK+FYM significantly increased the soil labile carbon (1378 and 1578mgkg−1, respectively), water soluble carbon (35.3 and 37.2mgkg−1, respectively) and water soluble carbohydrates (526 and 538mgkg−1, respectively) as compared to the control, where the corresponding values were 898, 16.8 and 464mgkg−1. The content of water stable aggregates organic carbon also increased with fertilization especially in combination with farmyard manure, whereas bulk density of soil was significantly reduced in the treatment of 100%NPK (1.49Mgm−3) and 100%NPK+FYM (1.46Mgm−3) over the control (1.60Mgm−3). The fertilizer treatments (100%N, 100%NP and 100%NPK) made a positive influence on soil organic carbon content in subsurface layers (15–60cm) also and it was more so in the treatment of 100%NPK+FYM as compared to the control, although contents did not differ significantly. Balanced fertilization (100%NPK) with and without FYM significantly improved the labile C content of soil (up to depth of 60cm) over the control. Balanced fertilization in combination with FYM significantly increased the water soluble carbon content of soil in comparison to the control (up to depth of 60cm). Bulk density of sub surface soil (15–60cm) was reduced in all the treatments as compared to the control although the treatment effect was non-significant. The rice–wheat cropping sequence thus, showed the potential of mitigating atmospheric carbon load through its sequestration and integrated nutrient management may further enhance this potential. [Copyright &y& Elsevier]

Abstract: Soil management practices may change the soil properties. The magnitude of the change varies according to the soil property, the climate, and the type and time of implementation of a particular management system. The aim of this study was to evaluate the effects of no-tillage (NT) on the chemical and biological properties of an Entic Haploxeroll in Central Chile. Soil organic carbon (SOC), microbial biomass and associated indicators , q Mic , q Min , available N, P and K, pH, electrical conductivity (EC), and crop yield were determined in a field experiment having a wheat (Triticum turgidum L.)–maize (Zea mays L.) crop rotation. The change in soil chemical properties was further evaluated using a greenhouse bioassay in which ryegrass (Lolium perenne L.) was grown in soil samples extracted at 0–2, 2–5, and 5–15cm depth. After nine years SOC in the NT treatment was 29.7Mgha−1 compared to 24.8Mgha−1 of CT, resulting in 4.98Mgha−1 C gain. The NT therefore resulted in an average annual sequestration of 0.55MgCha−1 yr−1 in the upper 15cm soil. The soil organic C stored under NT was mainly accumulated in the top 2-cm of soil. The biological indicators showed a greater biological soil quality under NT than under CT. Soil organic C was positively associated with available N, P, and K, but negatively with soil pH. The ryegrass bioassay yielded higher biomass in NT than CT. An improvement in the soil chemical quality of the NT soil was considered to be the main reason for this result. The maize yield under NT had the tendency to improve in time as compared to CT. Wheat, however, had lower yield under NT. It was concluded that NT increased C sequestration and SOC improving the chemical and biological properties of this soil. [Copyright &y& Elsevier]

Abstract: The enhancement of soil organic carbon (SOC) is important for sustainable agriculture, while changes in SOC depend on the balance between carbon (C) input and export. To investigate how chemical fertilizers contribute to C input (e.g. plant-derived C) and export (e.g. original SOC decomposition) in soil, a wheat (a C3 plant) pot experiment was conducted using a Phaeozem that had previously been used to cultivate maize (a C4 plant). The natural 13C abundance method was used to quantify wheat-derived SOC (WSC) and microbial respiration using the original SOC (R microbial) during the wheat growing season. The wheat grain, WSC, wheat-derived C (WDC: including WSC, root and stubble biomass C) and R microbial-derived CO2 emission (SCE) in fertilized treatments increased by 4.8–31.1%, 48.9–122.4%, 21.3–62.2% and 6.0–51.8%, respectively, when compared to unfertilized treatments. The total SOC in the post-experimental soil increased by 0.14–0.97% when compared to pre-experimental soil because the WSC input was larger than the SCE export, and it would be increased further if wheat root and stubble biomass C were included. Therefore, application of chemical fertilizer not only directly increases crop yield, but also indirectly contributes to C sequestration by favoring crop growth and crop-derived C input in soil. [Copyright &y& Elsevier]

Abstract: Growing interest in environmental quality has provided a strong incentive to examine how farming practices affect agricultural products’ carbon footprints (CF), an environmental quality indicator. This study determined (i) the CF of spring wheat (Triticum aestivum L.) grown in different cropping systems over 25 years, and (ii) the effect of soil organic carbon (SOC) changes over years on wheat CF. Wheat was grown in four cropping systems: (a) fallow-wheat (FW), (b) fallow-wheat-wheat (FWW), (c) fallow-wheat-wheat-wheat-wheat-wheat (FWWWWW), and (d) continuous wheat (ContW), in replicated field plots in Saskatchewan, Canada. Wheat CF was calculated at a system level with measured variables coupled with modeling approaches. Over the 25-year period, the soil under the ContW system gained organic C of 1340kgCO2 eqha−1 annually, or 38%, 55%, and 127% more than those gained in the FWWWWW, FWW, and FW systems, respectively. The SOC gain more than offset the greenhouse gas (GHG) emissions occurred during wheat production, leading to negative emission values at −742kgCO2 eqha−1 annually for ContW, and −459, −404, and −191kgCO2 eqha−1 for FWWWWW, FWW, and FW systems, respectively. Wheat in the ContW system produced the highest grain yield and gained highest SOC over the years, leading to the smallest (more negative) CF value at −0.441kgCO2 eqkg−1 of grain, significantly lower than the CF values from the three other systems (−0.102 to −0.116kgCO2 eqkg−1 of grain). Without considering the SOC gain in the calculation, wheat CF averaged 0.343kgCO2 eqkg−1 of grain and which did not differ among cropping systems. Wheat is the largest agricultural commodity in Saskatchewan, and the way the crop is produced has significant impacts on environmental quality, reflected by its carbon footprint. Cropping systems with decreased fallow frequency was shown to significantly enhance soil carbon gains over the years, increase annualized crop yields, and effectively lower the carbon footprint of this important commodity. [Copyright &y& Elsevier]

Abstract: Despite the significant growth in the number of published life-cycle assessments of biofuels, important aspects have not captured sufficient attention, namely soil carbon emissions from land use change (LUC) and uncertainty analysis. The main goal of this article is to evaluate the implications of different LUC scenarios and uncertainty in the life-cycle energy renewability efficiency and GHG (greenhouse gases) intensity of wheat-based bioethanol replacing gasoline. A comprehensive assessment of different LUC scenarios (grassland or cropland converted to wheat cultivation) and agricultural practices is conducted, which results in different carbon stock change values. The types of uncertainty addressed include parameter uncertainty (propagated into LC (life-cycle) results using Monte-Carlo simulation) and uncertainty concerning how bioethanol co-product credits are accounted for. Results show that GHG emissions have considerably higher uncertainty than energy efficiency values, mainly due to soil carbon emissions from direct LUC and N2O release from cultivated soil. Moreover, LUC dominates the GHG intensity of bioethanol. Very different GHG emissions are calculated depending on the LUC scenario considered. Conversion of full- or low-tillage croplands to wheat cultivation results in bioethanol GHG emissions lower than gasoline emissions, whereas conversion of grassland does not contribute to bioethanol GHG savings over gasoline in the short- to mid-term. [Copyright &y& Elsevier]

Abstract: Applying biochar to soil is an easy way to sequester carbon in soil, while it might reduce greenhouse gas (GHG) emissions and stimulate plant growth. The effect of charcoal application (0, 1.5, 3.0 and 4.5%) on GHG emission was studied in a wastewater sludge-amended arable soil (Typic Fragiudepts) cultivated with wheat (Triticum spp. L.) in a greenhouse. The application of charcoal at ≥1.5% reduced the CO2 emission rate significantly ≥37% compared to unamended soil (135.3 g CO2 ha−1 day−1) in the first two weeks, while the N2O emission rate decreased 44% when 4.5% charcoal was added (0.72 g N2O ha−1 day−1). The cumulative GHG emission over 45 days was 2% lower when 1.5% charcoal, 34% lower when 3.0% charcoal and 39% lower when 4.5% charcoal was applied to the sludge-amended soil cultivated with wheat. Wheat growth was inhibited in the charcoal-amended soil compared to the unamended soil, but not yields after 135 days. It was found that charcoal addition reduced the emissions of N2O and CO2, and the cumulative GHG emissions over 45 days, without altering wheat yield. [Copyright &y& Elsevier]

Abstract: The rhizosphere and the detritusphere are hot spots of microbial activity, but little is known about the interface between rhizosphere and detritusphere. We used a three-compartment pot design to study microbial community structure and enzyme activity in this interface. All three compartments were filled with soil from a long-term field trial. The two outer compartments were planted with maize (root compartment) or amended with mature wheat shoot residues from a free air CO2 enrichment experiment (residue compartment) and were separated by a 50 μm mesh from the inner compartment. Soil, residues and maize differed in 13C signature (δ13C soil −26.5‰, maize roots −14.1‰ and wheat residues −44.1‰) which allowed tracking of root- and residue-derived C into microbial phospholipid fatty acids (PLFA). The abundance of bacterial and fungal PLFAs showed clear gradients with highest abundance in the first 1–2 mm of the root and residue compartment, and generally higher values in the vicinity of the residue compartment. The δ13C of the PLFAs indicated that soil microorganisms incorporated more carbon from the residues than from the rhizodeposits and that the microbial use of wheat residue carbon was restricted to 1 mm from the residue compartment. Carbon incorporation into soil microorganisms in the interface was accompanied by strong microbial N immobilisation evident from the depletion of inorganic N in the rhizosphere and detritusphere. Extracellular enzyme activities involved in the degradation of organic C, N and P compounds (β-glucosidase, xylosidase, acid phosphatase and leucin peptidase) did not show distinct gradients in rhizosphere or detritusphere. Our microscale study showed that rhizosphere and detritusphere differentially influenced microbial C cycling and that the zone of influence depended on the parameter assessed. These results are highly relevant for defining the size of different microbial hot spots and understanding microbial ecology in soils. [Copyright &y& Elsevier]

We describe a summary model for the dynamics of carbon and nitrogen under varying weather, crop and soil conditions to investigate the role of soil organic carbon and nitrogen in yield formation in rice-based cropping systems of the Indo-Gangetic Plains (IGP). The model consists of three modules: soil organic matter (SOM), soil (SOIL), and crop growth (CROP). The SOM module consists of three pools: fresh, labile and stable. Carbon and nitrogen dynamics in the model are described in terms of carbon turnover, assimilation and dissimilation, with nitrogen linked through distinct C/N ratios. The SOIL module has two soil layers of variable depth (often 15cm each), and the labile and stable pools are replicated for these two layers. Water, crop and soil management practices and aeration characteristics of these layers affect the C and N dynamics of their respective pools. The CROP module calculates potential and actual biomass, leaf area index (LAI), evapotranspiration, total N demand, actual N uptake and N stress. Actual biomass is first partitioned between above (leaves, stem and storage organs) and below ground (roots and rhizodeposition), and a harvest index (HI) is applied to the aboveground biomass to calculate the yield. Independent data sets of 9 long-term experiments (LTEs) from the IGP of India were used for calibration and validation of the model. After calibration and validation, the model was used to explore the impact of various crop and soil management practices in rice-based cropping systems on different sites of the IGP. Overall, the model satisfactorily reproduced observed crop yields, SOC dynamics and total soil N dynamics for various cropping systems at different sites. Nitrogen mineralized from soil organic nitrogen contributed 5–75% to total N uptake in fertilized and non-fertilized treatments. With a recommended NPK application, a trend of significant decrease in simulated rice yield was found only at Ludhiana-3, and Pantnagar. Similarly, the simulated wheat yield also showed a significant trend of decline at Ludhina-3, Pantnagar and Barrackpore. Simulated SOC had a significant decline at Pantnagar, whereas at Ludhiana-3, it showed a significant increase. An increase in SOM is not always associated with an increase in yield, as the factor(s) improved by an increase in SOM may not be the limiting factor for crop growth. Depletion of many major macro (NPK) and micro (Zn, Fe, Mn, etc.) nutrients, essential for plant growth even with a balanced NPK fertilizer application and a maintained SOC, can lead to a decline in productivity. [Copyright &y& Elsevier]

Abstract: Soil organic carbon sequestration rates over 20 years based on the Intergovernmental Panel for Climate Change (IPCC) methodology were combined with local economic data to determine the potential for soil C sequestration in wheat-based production systems on the Indo-Gangetic Plain (IGP). The C sequestration potential of rice–wheat systems of India on conversion to no-tillage is estimated to be 44.1MtC over 20 years. Implementing no-tillage practices in maize–wheat and cotton–wheat production systems would yield an additional 6.6MtC. This offset is equivalent to 9.6% of India''s annual greenhouse gas emissions (519MtC) from all sectors (excluding land use change and forestry), or less than one percent per annum. The economic analysis was summarized as carbon supply curves expressing the total additional C accumulated over 20 year for a price per tonne of carbon sequestered ranging from zero to USD 200. At a carbon price of USD 25MgC−1, 3MtC (7% of the soil C sequestration potential) could be sequestered over 20 years through the implementation of no-till cropping practices in rice–wheat systems of the Indian States of the IGP, increasing to 7.3MtC (17% of the soil C sequestration potential) at USD 50MgC−1. Maximum levels of sequestration could be attained with carbon prices approaching USD 200MgC−1 for the States of Bihar and Punjab. At this carbon price, a total of 34.7MtC (79% of the estimated C sequestration potential) could be sequestered over 20 years across the rice–wheat region of India, with Uttar Pradesh contributing 13.9MtC. [Copyright &y& Elsevier]

Abstract: On sites where C4-plants have replaced C3-plants, changes in soil δ13C allow the turnover of C3- and C4-derived C to be separated. Studies of decadal scale turnover of soil C following conversion to C4-plants generally lack δ13C values for previous C4-residue inputs and assume that estimates of C4-derived soil C to be based on a fixed δ13C value. Further assumptions are that changes in the initial (time-zero) soil δ13C values are insignificant following conversion to C4-plants. We tested these assumptions by measuring: 1) the δ13C of annual samples of silage maize biomass (C4-plant) and winter wheat grains (C3-plant) grown during 1988 to 2006, and 2) the δ13C of soil kept under bare fallow during 1956 to 1983. The δ13C of plants was related to climate variables, and the impact of maize δ13C was based on estimates of maize-derived soil C using different approaches to establish the δ13C in maize inputs. The δ13C of both maize and wheat decreased with time, but the rate of change and annual variations were considerably larger for wheat than for maize. Maize as well as wheat δ13C was best related to year (probably reflecting a decrease in atmospheric δ13C) and the water balance during the active growth period. Using the smallest (−12.44‰) and the largest (−11.26‰) δ13C measured during 1988 and 2006, estimates of maize-derived C in soil after 18 years ranged from 13.2% to 14.2% of the soil total C. Despite a loss of 31% of the soil C pool under bare fallow, the increase in soil δ13C was significant only at P < 0.10. We conclude that annual variations in maize δ13C values and changes in the δ13C of the soil C fraction derived from the pre-conversion C3-vegetation have only little impact on estimates of maize-derived soil C that cover a few decades. For estimates covering several decades to centuries, the subtle but consistent changes in plant and soil δ13C need to be accounted for. The variability in δ13C in wheat grains suggest that the use of any fixed δ13C value for C3-residues in estimates of C turnover in soils on which C4-plants have been replaced by C3-plants can be associated with considerable uncertainty. [Copyright &y& Elsevier]

Abstract: Arbuscular mycorrhizal (AM) fungi improve soil quality by increasing soil structure stability through the glomalin (glomalin related soil protein, GRSP) production, but diverse tillage systems can differentially affect AM activity and the consequential GRSP content in soil. The aim of this study was to evaluate the effect of no-tillage (NT) and conventional tillage (CT) on AM fungal propagules (spore density, total and active fungal hyphae), GRSP content, and its relationship with some physical–chemical soil properties in a Mollisol from Central Chile. For this study, two plots managed for 6 and 10years under NT (NT6 and NT10), were compared with another plot maintained under CT management. In all cases a continuous spring wheat (Triticum turgidum L.)–maize (Zea mays L.) rotation was established. The number of mycorrhizal propagules, total soil carbon (T-C) and GRSP content in NT6 was higher compared to CT and NT10. This trend was also observed for water stable aggregates (WSA) and water drop penetration time. Significant relationships were found between total mycelium and GRSP (r =0.58, p <0.05), GRSP and WSA (r =0.66, p <0.01) and between GRSP and T-C (r =0.60, p <0.05), suggesting an active role of AM fungi and GRSP on soil aggregation, particularly under NT6 management. In addition, the long-term NT management (NT10) produced a decrease in the parameters here assayed which suggest the application of one moderate plowing when parameters such as T-C and/or GRSP show a decrease in long-term programs of reduced or NT management applied in medium/heavy soils. [Copyright &y& Elsevier]

Abstract: The issue of soil C sequestration is of special interest in Mediterranean areas, where, due to climatic conditions and agricultural practices, SOC (soil organic carbon) content is low, and is likely to be affected by climate change. Besides, losses of SOC have a relevant role in decreasing agricultural soil quality and could have a negative effect in productivity. Therefore, it is crucial to estimate whether modifying traditional soil management would have beneficial effects under future climate conditions. We used the EPIC model to simulate the interactive effect of climate change, CO2 enrichment, soil management (conventional tillage—CT vs. no tillage—NT) and two crop rotations, durum wheat–sunflower and durum wheat–maize, on crops yields and SOC in central Italy. The model was calibrated using soil and crop yield data collected from a long-term field experiment run in central Italy with CT and NT treatments. Maize and sunflower grain yields were significantly reduced by NT, primarily because of poor establishment, while durum wheat was almost not affected by tillage treatments. Projected durum wheat (Dw) and maize (Ma) grain yields were negatively affected by climate change (up to −25% and −10% respectively) while sunflower (Sf) yield increased. Tillage effects appear to be the most important factor in sequestering/releasing C. No-tillage practices sequestered in all profile (0–100cm depth) from 0.03 to 0.2tha−1 y−1 in 30 years, depending on climate scenario and plant C input, while conventional tillage (CT) led to massive C loss rates (up to −0.9tha−1 y−1). Beyond all uncertainties in the use of models, the results demonstrated that soil tillage and, to a certain extent, crop rotation, can play a relevant role in reducing (NT) or reinforcing (CT) the impact of climate change on SOC. No-tillage farming, if sufficient C input is ensured by the cropping system, could effectively contribute to increase soil C sequestration in Mediterranean rainfed environments. [Copyright &y& Elsevier]

Abstract: It is generally accepted that during the early stages of residue decomposition, easily available compounds are decomposed, leading to a relative increase in more recalcitrant compounds in the later stages of decomposition and that these changes in substrate availability are associated with changes in microbial community composition. However most studies on residue decomposition are conducted over several weeks or months; little is known about the changes in microbial community composition in the first weeks of decomposition. To address this knowledge gap, we incubated wheat residues inoculated with a microbial suspension in mesh bags buried in sand for 30 days, with sampling on days 0, 2, 4, 6, 8, 10, 15, 20, 25 and 30. Of the C added with the residues, 10, 18 and 25% had been respired on days 10, 20 and 30, respectively. The sum of PLFAs (phospholipid fatty acids), as an indicator of microbial biomass, increased strongly in the first 4 days and then decreased. The concentration of bacterial fatty acids was maximal on days 2 and 4, whereas the concentration of fungal fatty acids peaked on day 15. Microbial community composition (based on PLFA patterns) changed rapidly, with significant changes in the first 8 days and from day 8 to day 20. There were no significant changes in microbial community composition after day 20. The concentration of water-soluble C decreased strongly in the first 8 days, suggesting that the rapid changes in microbial community in this period are related to the changes in water-soluble C. Residue C chemistry, assessed by 13C NMR spectroscopy, changed little during the incubation period. This study showed that microbial community composition in decomposing residues changes rapidly in the first 1–2 weeks, which is, at least partly, the result of competition for the easily available compounds in the water-soluble fraction. After depletion of the water-soluble compounds, the microbial community composition changes more slowly. [Copyright &y& Elsevier]

Abstract: Soil organic matter (SOM) is the main energy resource of the great diversity of soil invertebrates but knowledge on the contribution of SOM pools of different ages to soil animal nutrition is sparse. In the present study natural stable isotope ratios were used to investigate the incorporation of decade old wheat-borne carbon into soil invertebrates of different trophic levels of a maize field 27 years after the replacement of wheat. For comparison a nearby continuous wheat field was investigated. Although the soil food web of the wheat and the maize field consisted of similar invertebrate taxa, most taxa were significantly more abundant in the wheat than in the maize field confirming that C4 plants are generally of poor food quality to soil animals due to low nutrient and high fibre contents. However, different cultivation strategies may also have contributed to differences in the abundance of invertebrates between both study sites. The mean incorporation of C3 carbon in soil animals in the maize field was 60.6±27.8%, but significantly differed between invertebrate species. Unfortunately, the field size did not entirely exclude incorporation of C3 carbon into the tissue of large and mobile invertebrates by feeding on C3 resources outside of the maize field. However, less mobile species such as endogeic earthworms incorporated high amounts of C3 carbon presumably due to the mobilisation of old carbon pools enclosed in soil aggregates and inaccessible to other soil invertebrates during gut passage. Furthermore, small and less mobile invertebrate species, such as most hemi- and epiedaphic Collembolans, also incorporated high amounts of C3 carbon likely by feeding on saprophytic fungi and microorganisms. In contrast, euedaphic Collembola incorporated only small amounts of C3 carbon suggesting preferentially feeding on maize resources. Overall, our data suggest that decade old carbon resources form an important component of the soil animal food web, but that the exploitation of old carbon resources by animal species varies with their distribution within the soil matrix, trophic position and exploitation of algae, and as an artefact to the small size of the study site, animal mobility. [Copyright &y& Elsevier]

Abstract: Biofuels can be produced by converting cellulose in crop residues to ethanol. This has recently been viewed as a potential supplement to non-renewable energy sources, especially in the Americas. A 50-yr field experiment was analyzed to determine the influence of (i) removing approximately 22% of the above-ground wheat (Triticum aestivum L.) residue each crop year, and (ii) N and P fertilization on soil carbon (C) in the top 15cm depth of a fallow–wheat–wheat (F–W–W) rotation. The study was conducted from 1958 to 2007 on a clay soil, at Indian Head in sub-humid southeast Saskatchewan, Canada. Soil C concentrations and bulk densities were measured in the 0–7.5 and 7.5–15cm depths in 1987, 1996 and 2007 and soil C changes were related to C inputs estimated from straw and root yields calculated from regressions relating these to grain yields. Two soil organic matter models [the Campbell model and the Introductory Carbon Balance Model (ICBM)] were also used to simulate and predict the effects of the treatments on soil C change over time, and to estimate likely soil C change if 50% or 95% of above-ground residues were harvested each crop year. Crop residue removal reduced cumulative C inputs from straw and roots over the 50-yr experiment by only 13%, and this did not significantly (P >0.05) reduce soil C throughout the experiment duration. However, after 50yr of applying N fertilizer at recommended rates, soil C increased significantly by about 3Mgha−1 compared to the non-fertilized treatment. The simulated effect of removing 50% and 95% of the above-ground residues suggested that removing 50% of the straw would likely have a detectable effect on the soil C, while removing 95% of the straw certainly would. Measurements and model simulations suggest that adoption of no-tillage without proper fertilization will not increase soil C. Although it appears that a modest amount of residue may be safely removed from these Udic Borolls (Black Chernozems) without a measurable effect on soil C, this would only be feasible if accompanied by appropriate fertility management. [Copyright &y& Elsevier]

Abstract: The Loess Plateau in northwest China is one of the most eroded landscapes in the world, and it is urgent that alternative practices be evaluated to control soil erosion. Our objective was to determine how three different tillage practices for monoculture of winter wheat (Triticum aestivum L.) affected soil organic carbon (SOC) and N content after 11 years. Conventional tillage with residue removal (CT), shallow tillage with residue cover (ST), and no-tillage with residue cover (NT) were investigated. Carbon and N in various aggregate-size classes and various labile organic C fractions in the 0–15- and 15–30-cm soil layers were evaluated. The ST and NT treatments had 14.2 and 13.7% higher SOC stocks and 14.1 and 3.7% higher total N (Nt) stocks than CT in the upper 15cm, respectively. Labile C fractions: particulate organic C (POC), permanganate oxidizable C (KMnO4-C), hot-water extractable C (HWC), microbial biomass C (MBC) and dissolved organic C (DOC) were all significantly higher in NT and ST than in CT in the upper 15cm. KMnO4-C, POC and HWC were the most sensitive fractions to tillage changes. The portion of 0.25–2mm aggregates, mean weight diameter (MWD) and geometric mean diameter (GMD) of aggregates from ST and NT treatments were larger than from CT at both 0–15- and 15–30-cm soil depths. The ST and NT treatments had significantly higher SOC and Nt in the 0.25–2mm fraction at both depths and significantly higher Nt content in the upper 15cm. Positive significant correlations were observed between SOC, labile organic C fractions, MWD, GMD, and macroaggregate (0.25–2mm) C within the upper 15cm. We conclude that both variants of conservation tillage (NT and ST) increase SOC stock in the rainfed farming areas of northern China and are therefore more sustainable practices than those currently being used. [Copyright &y& Elsevier]

Abstract: Rising levels of atmospheric CO2 have often been found to increase above and belowground biomass production of C3 plants. The additional translocation of organic matter into soils by increased root mass and exudates are supposed to possibly increase C pools in terrestrial ecosystems. Corresponding investigations were mostly conducted under more or less artificial indoor conditions with disturbed soils. To overcome these limitations, we conducted a 14CO2 pulse-labelling experiment within the German FACE project to elucidate the role of an arable crop system in carbon sequestration under elevated CO2. We cultivated spring wheat cv. “Minaret” with usual fertilisation and ample water supply in stainless steel cylinders forced into the soil of a control and a FACE plot. Between stem elongation and beginning of ripening the plants were repeatedly pulse-labelled with 14CO2 in the field. Soil born total CO2 and 14CO2 was monitored daily till harvest. Thereafter, the distribution of 14C was analysed in all plant parts, soil, soil mineral fractions and soil microbial biomass. Due to the small number of grown wheat plants (40) in each ring and the inherent low statistical power, no significant above and belowground growth effect of elevated CO2 was detected at harvest. But in comparison to ambient conditions, 28% more 14CO2 and 12% more total CO2 was evolved from soil under elevated CO2 (550 μmol CO2 mol−1). In the root-free soil 27% more residual 14C was found in the FACE soil than in the soil from the ambient ring. In soil samples from both treatments about 80% of residual 14C was found in the clay fraction and 7% in the silt fraction. Very low 14C contents in the CFE extracts of microbial biomass in the soil from both CO2 treatments did not allow assessing their influence on this parameter. Since the calculated specific radioactivity of soil born 14CO2 gave no indication of an accelerated priming effect in the FACE soil, we conclude that wheat plants grown under elevated CO2 can contribute to an additional net carbon gain in soils. [Copyright &y& Elsevier]

Abstract: In areas where two crops are grown per year or three crops every 2 years, the status of residual soil nutrients after the harvest of the first crop is critical to the crop to be grown immediately after, while the postharvest soil nutrient status can be influenced by irrigation applied to the test crop. This study determined the effect of various soil water treatments applied to the test crop on the status of postharvest residual soil nutrient pools in an arid environment. Spring wheat (Triticum aestivum L.) was grown as test crop under conditions of full- (as control), high-, moderate-, and low-water conditions during jointing, booting-heading, and grain filling stages, in 2003 and 2004. Compared to the control, grain yield and water use efficiency (WUE) were significantly increased by subjecting the wheat crop to moderate-water conditions during various growth stages, and low-water conditions at jointing stage in both years. Soil C at harvest decreased linearly with increased grain yield of the test crop. Moderate- to high-water conditions during jointing stage resulted in 12–24% greater soil C in the top 40cm depth in 2003, with a marginal difference in 2004. Water treatments impacted the status of residual soil nutrients in 2003; soil total N and available soil P in the top 40cm depth were significantly higher in low- to moderate-water treatments compared to the control, while in 2004 significantly higher total N and P, available N, P and K were found only in the top 20cm depth. Increased yield of wheat test crop with moderate-water resulted in increased postharvest residual soil nutrients, whereas the ratios of C/N, C/P, and C/K were largely influenced by years and were less related to water treatments. We conclude that the determination of postharvest soil C and nutrient elements may provide useful information in monitoring potential changes of soil nutrient status over time in the intensified cropping systems, and that the recommendation of fertilization for the crop to be grown immediately following the first crop can be established by simply analyzing the productivity of the first crop without intensive measurements of soil nutrients. [Copyright &y& Elsevier]

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]

Abstract: A spatially referenced biophysical model, the water and nitrogen management model (WNMM), was developed and shown to simulate dynamic soil water movement and soil–crop carbon (C) and nitrogen (N) cycling under a given agricultural management, for the purpose of identifying optimal strategies for managing water and fertiliser N under intensive cropping systems (mainly wheat–maize) in the North China Plain and other regions in the world. A uniform data structure, ARC GRID ASCII format, was used both in GIS and WNMM for achieving a close Model-GIS coupling. A significant part of WNMM adopts and modifies concepts and components from widely used models, with a focus on soil N transformations. WNMM simulates the key processes of water dynamics in the surface and subsurface of soils: including evapotranspiration, canopy interception, water movement and groundwater fluctuations; heat transfer and solute transport; crop growth; C and N cycling in the soil–crop system; and agricultural management practices (crop rotation, irrigation, fertiliser application, harvest and tillage). The model runs on a daily time step at any desired scale and is driven by lumped variables (meteorological and crop biological data) in text data format, and spatial variables (soil and agricultural management) in ARC GRID ASCII format. In particular, WNMM simulates all key N transformations in agricultural fields, including mineralisation of fresh crop residue N and soil organic N, formation of soil organic N, immobilisation in biomass, nitrification, ammonia (NH3) volatilisation, denitrification and nitrous oxide (N2O) emissions. WNMM has been successfully applied in Fengqiu County, Henan Province and Luancheng County, Hebei Province, China at site and regional scales. The key WNMM components were intensively calibrated and verified against comprehensive field measurements of soil water content, evapotranspiration, crop leaf area index and yield, NH3 volatilisation, denitrification and N2O emissions as well as nitrate (NO3 −)–N concentrations in the soil solution. A sensitivity analysis showed that WNMM was sensitive to changes in meteorological variables, soil hydraulic properties, land use and agricultural management. At the site scale, WNMM simulated well soil water content, crop growth and yield, NH3 volatilisation and soil NO3 −–N concentration. There was uncertainty in simulating soil denitrification and N2O emissions, when the predicted peaks of denitrification and N2O emissions at very wet conditions could not be confirmed because of limitations in the acetylene-inhibition method for measuring denitrification. At county scale, WNMM simulation of crop yield in Fengqiu County explained 22% of the variation in observed crop yields, and 31% of crop yield variation in Luancheng County where soil variation was less. These results are considered acceptable because factors such as soil salinity and other nutrient deficiencies, which have not been considered in this version of WNMM, may play a role. The source code for the WNMM is available on request. [Copyright &y& Elsevier]

Abstract: Soil respiration is a process influenced by land use, management practices, and environmental conditions. Our objectives were to evaluate relationships between management-induced differences in soil organic carbon (SOC) and soil CO2 efflux from continuous no-till spring wheat (Triticum aestivum L.), spring wheat-fallow under no-till, and a native mixed-grass prairie with grazing near Mandan, ND. A Werner–Sen–Chama soil complex (Entic Haplustoll, Typic Haplustoll, and Typic Calciustoll) was present at the grassland site and a Wilton silt loam (Pachic Haplustoll) at the cropping sites. Soil chambers were used to measure soil CO2 effluxes about every 21 days starting 14 May 2001 to 1 April 2003. Soil water and soil temperature were measured at time of CO2 efflux measurements. Soil organic carbon, microbial biomass carbon (MBC), and above and belowground plant biomass were measured in mid-July each year. Root biomass to 0.3m depth of the undisturbed grassland was significantly greater (12.3Mgha−1) than under continuous wheat (1.3Mgha−1) and wheat-fallow (0.3Mgha−1). Grassland SOC content of 84Mgha−1 to 0.3m soil depth was 1.2 times greater than continuous wheat and 1.3 times greater than wheat-fallow. The MBC of the grassland was 2.2Mgha−1, or 3.6 times greater than continuous wheat and 7.2 times greater than wheat-fallow treatments. Soil CO2 efflux averaged 2.8gCO2–Cm−2 day−1 for grassland, compared to 1.9gCO2–Cm−2 day−1 for wheat fallow and 1.6gCO2–Cm−2 day−1 for continuous wheat treatments. Although these CO2 efflux rates were based on measurements made at intervals of about 21 days, the differences among treatments with time were rather consistent. Differences in soil CO2 efflux among treatments could be attributed to differences in SOC and MBC, suggesting that land use plays a significant role in soil CO2 efflux from respiration. [Copyright &y& Elsevier]

Conservation tillage has become a major soil management strategy to reduce soil erosion and improve soil quality, yet the impacts of crop rotation on soil responses to conservation tillage remain poorly described. We investigated the effects of (i) perennial grass cover versus annual cropping and (ii) type of break crop in a wheat (Triticum aestivum L.)-based crop rotation system on surface-soil (0–10 cm) structural and organic matter properties towards the end of a decade of continuous management on an Albic Luvisol in the cold, semiarid region of northwestern Canada. Soil aggregation was at state to resist water erosion more under perennial grass (i.e. bromegrass (Bromus inermis Leyss.) and red fescue (Festuca rubra L.)) than under annual cropping systems (mean-weight diameter of 2.1 and 1.6 mm under perennial and annual systems, respectively). Soil organic C was higher (44 g C kg−1 soil versus 38 g C kg−1 soil), but total soil N was lower (3.5 g N kg−1 soil versus 3.9 g N kg−1 soil) under perennial compared with annual cropping systems. There were few significant differences in soil-structural properties among the various annual cropping systems. The largest effect was greater light-fraction C and N under continuous wheat (4.0 g C kg−1 soil and 0.27 g N kg−1 soil) compared with other rotations, especially wheat–wheat–fallow (2.4 g C kg−1 soil and 0.16 g N kg−1 soil), as a result of higher residue inputs. Relationships between mean-weight diameter of water-stable aggregates and biochemical properties were strongest for soil microbial biomass C and soil organic C. Perennial grass cover exhibited greater potential to preserve soil-structural properties than no-tillage annual cropping. [Copyright &y& Elsevier]

• 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]