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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]

Decline in soil organic carbon (SOC) due to intensive tillage and removal or burning of crop residues is considered a major threat to maintaining soil quality and meeting future challenges of food production at national and global scales. Adoption of conservation-agriculture practices (no till and residue retention) is necessary to promote soil structural stability and increases in SOC content and enzyme activities. We evaluated the impact of tillage and residue-management practices on yield, soil labile-C pools, aggregate stability and soil enzyme activities after seven cycles of a rice (Oryza sativa L.)–wheat (Triticum aestivum L.) system on the Indo-Gangetic Plain of India. Treatments included four combinations of tillage and crop establishment in rice (main plots), and three combinations of tillage and residue management in wheat (subplots). Irrespective of rice-establishment method, mean grain yield of no-till wheat with rice-residue mulch (NTW+RR) was 9% and 22% higher, respectively, than of conventional-till (CTW) or no-till wheat with no rice-residue mulch. Soil C pools (very labile, labile, less-labile and non-labile) were significantly higher under a no-till dry-seeded rice (NTDSR)–NTW+RR cycle than conventional-till puddled transplanted rice–CTW. Macro-aggregates (>0.25 mm) had higher labile C pools, glomalin content and enzyme activities than micro-aggregates. NTW+RR significantly increased soil C pools within both macro- and micro-aggregates. Compared with CTW, NTW+RR increased soil dehydrogenase, cellulase and alkaline phosphatase activities by 23%, 34% and 14%, and water-soluble organic C by 31%, and increased water-stable aggregates and mean-weight-diameter. NTDSR–NTW+RR increased SOC, enzyme activity, aggregate stability and wheat grain yield. Results indicated that soil labile-C pools across aggregate fractions were the most sensitive indicators of soil quality when determining the effects of changes in management practices. Furthermore, adoption of no till and residue retention may improve sustainability in rice–wheat systems of the Indo-Gangetic Plain. This 7-year study examined soil carbon pools, aggregate stability, enzyme activities and wheat yield under conservation and conventional tillage and residue-management practices in a rice–wheat system on the Indo-Gangetic Plain. Macro-aggregates (>0.25 mm) had higher labile C pools, glomalin content and enzyme activities than micro-aggregates. The combination of no-till direct-seeded rice with no-till wheat + rice residue increased SOC, soil enzyme activities, aggregate stability and wheat grain yield, indicating that adoption of no till and residue retention may improve sustainability in these rice–wheat systems. [ABSTRACT FROM AUTHOR]

Carbon (C) mineralization of crop residues is an important process occurring in soil which is helpful in predicting CO2 emission to the atmosphere and nutrient availability to plants. A laboratory experiment was conducted in which C mineralization of residues of rice (Oryza sativa), wheat (Triticum aestivum), maize (Zea mays), mungbean (Vigna radiata) and their mixtures was applied to the soil surface or incorporated into an Alfisols from Northwest India. C mineralization was significantly affected by residue placement and type and their interactions. Rice residue had a higher decomposition rate (k = 0.121 and 0.076 day−1) than wheat (0.073 and 0.042 day−1) and maize residues (0.041 day−1) irrespective of placements. Higher decomposition rates of rice and wheat were observed when placed on soil surface than incorporated in the soils. Additive effects of the contribution of each residue type to C mineralization of the residue mixture were observed. When mungbean residue was added to the rice/wheat or maize/wheat mixture, decomposition of the residue mixture was enhanced. Crop residues with low N and high C/N ratio such as maize, wheat, rice and their mixtures can be applied on the soil surface for faster C and N mineralization, thereby helping to manage high volumes of residues under conservation agriculture-based practices in northwest India. [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]

Agricultural production must increase to feed a growing and wealthier population, as well as to satisfy increasing demands for biomaterials and biomass-based energy. At the same time, deforestation and land-use change need to be minimized in order to preserve biodiversity and maintain carbon stores in vegetation and soils. Consequently, agricultural land use needs to be intensified in order to increase food production per unit area of land. Here we use simulations of AgMIP’s Global Gridded Crop Model Intercomparison (GGCMI) phase 1 to assess implications of input-driven intensification (water, nutrients) on crop yield and yield stability, which is an important aspect in food security. We find region- and crop-specific responses for the simulated period 1980–2009 with broadly increasing yield variability under additional nitrogen inputs and stabilizing yields under additional water inputs (irrigation), reflecting current patterns of water and nutrient limitation. The different models of the GGCMI ensemble show similar response patterns, but model differences warrant further research on management assumptions, such as variety selection and soil management, and inputs as well as on model implementation of different soil and plant processes, such as on heat stress, and parameters. Higher variability in crop productivity under higher fertilizer input will require adequate buffer mechanisms in trade and distribution/storage networks to avoid food price volatility. [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]

Perennial grasses have been promoted to supply cellulose for ethanol production but possible consequences on soil organic carbon (SOC) should be assessed before adoption in a given region. Specific objectives were to (i) compare aboveground biomass C production and depth distribution of SOC content of continuous winter wheat (Triticum aestivum L.) and switchgrass (Panicum virgatum L.), (ii) determine the contribution of switchgrass to SOC, and (iii) characterize soil C inventories under each crop across a wide range of precipitation regimes. A 6-yr (2008–2013) field study with winter wheat and switchgrass ‘Blackwell’ was conducted in northeastern Oregon. Solid set sprinkler irrigation was used to create a productivity gradient of low, medium, and high precipitation levels. The contribution of switchgrass to SOC was identified with δ13C measurements. Winter wheat had significantly higher 5-yr-average aboveground biomass C production than switchgrass across precipitation levels and winter wheat under high precipitation produced significantly higher aboveground biomass C than medium and low precipitation. After 5-yr of cropping, SOC accrual in the 0- to 15-cm depth was significantly higher under winter wheat than switchgrass in each precipitation regime. Results of δ13C indicated switchgrass contributed 7.9, 8.5, and 12.9% to profile SOC at low, medium, and high precipitation levels. Soil organic carbon in dry cropland is resistant to a shift in crop species. Switchgrass does not increase SOC more than continuous winter wheat in dry cropland of the semiarid Pacific Northwest. [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]

Background: Differences in cropping systems and their impacts on plant growth and carbon (C) uptake as well as soil C release pose a major challenge in projecting agroecosystem C balance. Methods: A four-year (2012-2015) field experiment was conducted to examine crop C uptake and soil respiration in two conventional (wheat-cotton and wheat-maize) and two legume-based (wheat-soybean and alfalfa-maize) double-season cropping systems in North China Plain. Results: During the 4 experimental years, crop C uptake was greater in the two conventional systems than the two legume-based systems. However, soil respiration was higher in the two systems with C (i.e. maize) than C crops (i.e. cotton and soybean) planted in summer. As consequences, cropland C balance was positive in the two conventional cropping systems, with greater value in the wheat-maize comparing to wheat-cotton system. However, the two legume-based cropping systems showed negative cropland C balance. Conclusions: Our findings indicate that, although more CO-C is emitted in maize-related cropping systems, the conventional agricultural activities may sequestrate more C in comparison with the legume-based farming in North China Plain due to higher C uptake, and highlight the importance of management strategy in improving agroecosystem C storage. [ABSTRACT FROM AUTHOR]

Straw return is a promising method for managing soil organic carbon (SOC) in agricultural soils and thus may promote sustainable land use. However, the optimal straw-return strategy for economically sustainable grain production in intensive winter wheat (Triticum aestivum L.)-summer maize (Zea mays L.) cropping systems remains uncertain. A 4-yr field experiment was conducted in the central North China Plain to determine the effects of straw return on SOC stock and lability, soil enzyme activity, and grain yield, and to further evaluate the sustainability of crop production in intensive wheat-maize double-cropping systems. Four treatments were tested: no straw return (NR), return of wheat straw (WR), return of maize straw (MR), and return of both wheat and maize straw (WR+MR). Compared with the initial value, SOC stocks significantly increased by 2.8, 5.4, and 13.1% in WR, MR, and WR+MR, respectively, and significantly decreased by 2.9% in NR. Stocks of KMnO4-oxidizable C and microbial biomass C; activities of soil invertase, protease, and dehydrogenase; and the C management index were significantly higher with than without straw return and followed the order NR < WR < MR < WR+MR. Yields of wheat and maize were highest in WR+MR, but economic sustainability was higher in WR and MR relative to NR and WR+MR. Our results indicate that return of either wheat or maize straw is sufficient to maintain SOC levels and may be the optimal strategy for economically sustainable grain production in the central North China plain. [ABSTRACT FROM AUTHOR]

Soil organic carbon (SOC) is an important and manageable property of soils that impacts on multiple ecosystem services through its effect on soil processes such as nitrogen (N) cycling and soil physical properties. There is considerable interest in increasing SOC concentration in agro-ecosystems worldwide. In some agro-ecosystems, increased SOC has been found to enhance the provision of ecosystem services such as the provision of food. However, increased SOC may increase the environmental footprint of some agro-ecosystems, for example by increasing nitrous oxide emissions. Given this uncertainty, progress is needed in quantifying the impact of increased SOC concentration on agro-ecosystems. Increased SOC concentration affects both N cycling and soil physical properties (i.e., water holding capacity). Thus, the aim of this study was to quantify the contribution, both positive and negative, of increased SOC concentration on ecosystem services provided by wheat agro-ecosystems. We used the Agricultural Production Systems sIMulator (APSIM) to represent the effect of increased SOC concentration on N cycling and soil physical properties, and used model outputs as proxies for multiple ecosystem services from wheat production agro-ecosystems at seven locations around the world. Under increased SOC, we found that N cycling had a larger effect on a range of ecosystem services (food provision, filtering of N, and nitrous oxide regulation) than soil physical properties. We predicted that food provision in these agro-ecosystems could be significantly increased by increased SOC concentration when N supply is limiting. Conversely, we predicted no significant benefit to food production from increasing SOC when soil N supply (from fertiliser and soil N stocks) is not limiting. The effect of increasing SOC on N cycling also led to significantly higher nitrous oxide emissions, although the relative increase was small. We also found that N losses via deep drainage wereminimally affected by increased SOC in the dryland agro-ecosystems studied, but increased in the irrigated agro-ecosystem. Therefore, we show that under increased SOC concentration, N cycling contributes both positively and negatively to ecosystem services depending on supply, while the effects on soil physical properties are negligible. [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]

The aim of this study was to assess the changes in soil organic carbon (SOC) stock in relation to the carbon (C) input from nine wheat-based cropping systems and untilled grass. The SOC pool ranged from 32.1 to 49.4 Mg ha−1at 0–20 cm and from 94 to 171 Mg ha−1at 0–100 cm for the arable soil, while in untilled grassland, it was higher (54 and 185 Mg C ha−1, respectively). SOC stock was observed to be lower at the unfertilized 2-year rotation and higher at the 4-year rotation with manure and mineral fertilization. The study showed a winter wheat yield decrease of 176.8 kg ha−1for a 1- Mg ha−1SOC stock change in the 0–20-cm soil depth. The estimated C input for SOC stock maintenance was from 266 to 340 g C m−2 year−1for winter wheat and rotations, respectively. Additional C input did not increase the SOC pool, suggesting that arable plots had a limited ability to increase SOC. These results provide guidance for the selection of management practices to improve C sequestration. [ABSTRACT FROM PUBLISHER]

Background and aims: Soil degradation is a major global problem; to investigate the potential for recovery of soil biota and associated key functions, soils were monitored during the early years of conversion between permanent grassland, arable cropping and bare fallow (maintained by regular tilling). Distinct differences in soil properties had become apparent 50 years after a previous conversion. Methods: Subplots on previously permanent grassland, arable and bare fallow soil were converted to the two alternatives, generating 9 treatments. Soil properties (soil organic carbon, mesofauna, microbial community structure and activity) were measured. Results: After 2 years, mesofauna and microbial abundance increased where plants were grown on previously bare fallow soils and declined where grassland was converted to bare fallow treatment. Overall prokaryote community composition remained more similar to the previous treatments of the converted plots than to the new treatments but there were significant changes in the relative abundance of some groups and functional genes. Four years after conversion, SOC in arable and bare fallow soils converted to grassland had increased significantly. Conclusions: Conversion to permanent grassland effectively replenished C in previously degraded soil; the soil microbiome showed significant conversion-related changes; plant-driven recovery was quicker than C loss in the absence of plants. [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]

Lime application is the most common method to improve crop production in acid soils and has been shown to change soil organic C content. However, the impact of liming history on the priming effect on soil organic C is not well understood. This study examined the effect of liming history on C priming in response to the addition of crop residues of different qualities. Soils with pH ranging from 4.7 to 7.4 were collected from two adjacent field experiments whereby lime was applied at different rates, 6 and 35 years ago. A 90-day incubation study was conducted by applying C-labelled wheat (C/N 42) and field-pea (C/N 29) residues at a rate of 5 g kg soil. Residue application to soils yielded the positive priming effect in all pH levels with the magnitude of C priming being the greatest at initial soil pH 6.6. In comparison, the optimal pH for residue decomposition (7.3) was higher than that for priming. The overall priming effect was about 17% greater with field-pea than wheat residue. However, cumulative decomposition of added field-pea residue was 15% lower than that of wheat residue. Furthermore, C priming was greater in soils from the 35-year-old than the 6-year-old limed plots, indicating that a longer history of liming did not enhance the protection of indigenous C from mineralization. The results suggest that increases in soil pH by liming enhanced native C priming through greater microbial biomass and activity and that the magnitude and dynamics of the priming effect largely depended on residue quality and its consequent nutrient supply to decomposer organisms. The study implies that over-liming would likely have negative impacts on the long-term C sequestration. [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]

Aims: The study aimed to find soil parameters that are best related to Se plant uptake for low Se soils with predominantly organic Se, and to explore the mechanisms that control Se bioavailability in the soils under study. Methods: A pot experiment using nineteen soil samples taken from different fields of arable land (potato fields) in the Netherlands was conducted on summer wheat ( Triticum aestivum L.). Selenium in wheat shoots and soil parameters, including basic soil properties, C:N ratio, inorganic selenite content, and Se and organic C in different soil extractions (0.01 M CaCl, 0.43 M HNO, hot water, ammonium oxalate, aqua regia) were analysed. Regression analysis was performed to identify soil parameters that determine Se content in wheat shoots. Results: The regression model shows that Se:DOC ratio in 0.01 M CaCl soil extraction explained about 88 % of the variability of Se uptake in wheat shoots. Selenium uptake increased with Se:DOC ratio in CaCl extraction, which can be interpreted as a measure of the content of soluble Se-rich organic molecules. Selenium:DOC ratio in CaCl extraction and Se uptake increased towards higher soil pH and lower soil C:N ratio. The soil C:N ratio is also negatively correlated to Se:organic C ratio in other extractions (0.43 M HNO, hot water, ammonium oxalate, aqua regia), indicating that at low soil C:N ratio soil organic matter is richer in Se. Contrarily, the soil pH is positively and strongly correlated to Se:organic C ratio in CaCl and hot water extractions, but only weakly correlated to Se:organic C ratio in other extractions. Conclusions: Selenium-rich dissolved organic matter is the source of bioavailable Se in low Se soils with predominantly organic Se. The soil pH and quality of soil organic matter (i.e. soil C:N ratio) are the main soil properties determining Se bioavailability in these soil types. [ABSTRACT FROM AUTHOR]

Understanding of crop residue mineralization is imperative for crop residue management in crop production. C and N mineralization dynamics of rice and wheat residues under surface applied and soil incorporated conditions were evaluated in an incubation experiment. Both rice and wheat residues were incorporated and surface applied. Soil moisture was maintained at 18% w/w (≈ - 15 kPa) during course of study. Periodic determinations on CO2-C and N mineralized were performed over a period of 120 days. The highest peaks for CO2-C occurred during the first week of the incubation period. Significantly higher emission of CO2-C occurred from rice and wheat incorporation treatments (50%) followed by surface application treatments (19%) as compared to control soil. Variations between rice and wheat residue either incorporated or surface applied were non-significant. Both rice and wheat residues either incorporated or surface applied immobilized soil mineral N. Peak for N immobilization in the incorporated treatments was on day 15 and then started mineralization while surface applied wheat and rice residue decreased soil mineral nitrogen gradually and continuously up to 75th day of incubation. Incorporated residues increased soil organic carbon and soil aggregate stability significantly by 18% and 55% over control respectively. This study indicated that crop residues incorporated into the soil have higher decomposition rate with a quicker mineral N release, more organic matter build up and soil structure improvement than retaining crop residues at the soil surface. [ABSTRACT FROM AUTHOR]

The maintenance and accumulation of soil organic carbon (SOC) in agricultural systems is critical to food security and climate change, but information about the dynamic trend and efficiency of SOC sequestration is still limited, particularly under long-term fertilizations. In a typical Purpli-Udic Cambosols soil under subtropical monsoon climate in southwestern China this study thus estimated the dynamic, trend and efficiency of SOC sequestration after 22-year (1991-2013) long-term inorganic and/or organic fertilizations. Nine fertilizations under a rice-wheat system were examined: control (no fertilization), N, NP, NK, PK, NPK, NPKM (NPK plus manure), NPKS (NPK plus straw), and 1.5NPKS (150% NPK plus straw). Averagely, after 22-years SOC contents were significantly increased by 4.2-25.3% and 10.2-32.5% under these fertilizations than under control conditions with the greatest increase under NPKS. The simulation of SOC dynamic change with an exponential growth equation to maximum over the whole fertilization period predicted the SOC level in a steady state as 18.1 g kg−1 for NPKS, 17.4 g kg−1 for 1.5NPKS, and 14.5-14.9 g kg−1 for NK, NP, NPK, and NPKM, respectively. Either inorganic, organic or their combined fertilization significantly increased crop productivity and C inputs that were incorporated into soil ranging from 0.91 to 4.63 t (ha · y)−1. The C sequestration efficiency was lower under NPKM, NPKS, and 1.5NPKS (13.2%, 9.0%, and 10.1%) than under NP and NPK (17.0% and 14.4%). The increase of SOC was asymptotical to a maximum with increasing C inputs that were variedly enhanced by different fertilizations, indicating an existence of SOC saturation and a declined marginal efficiency of SOC sequestration. Taken all these results together, the combined NPK plus straw return is a suitable fertilizer management strategy to simultaneously achieve high crop productivity and soil C sequestration potential particularly in crop rotation systems. [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]

Depth distribution of soil organic carbon (SOC) fractions depends on the efficiency of agro-technical managements. Information on depth distribution of SOC fractions mostly confined to the plow layer and scant in dry lands of Punjab, Pakistan. Therefore, a field experiment was laid out with moldboard plow (MP) (control), tine cultivator (TC), and minimum tillage (MT) as main plots, and cropping sequences fallow wheat ( Triticum aestivum L.), (FW, control), mungbean ( Vigna radiata L.) wheat (MW), sorghum ( Sorghum bicolor L.) wheat (SW), green manure wheat (GW), and mungbean-chickpea (MC) ( Cicer arietinum L.) as sub-plots. Treatment effects were assessed for microbial biomass carbon (MBC), potentially mineralizeable carbon (PMC), particulate organic carbon (POC), dissolved organic carbon (DOC), HCl insoluble carbon (HIC), and stratification ratio (SR) in Rawal series: Udic Haplustalf. Alfisols. The MBC concentration was the highest in MT system, at 15 to 30-cm depth under MW and PMC concentration was highest under SW with MT at 45-60 cm. MP had higher POC in FW sequence. The highest DOC was at 0 to 15-cm depth under MC with TC and stock of HIC was more under TC with FW sequence. The highest SR of PMC was under MT with FW at 0-15:15-30 and POC was under TC and MP with FW at depths of 0-15:45-60 cm. The highest SR for DOC was under MP with GW at 0-15:45-60 cm and HCl insoluble C was under MT with SW at 0-15:45-60. In broad-spectrum, labile organic fractions revealed differential sensitivity, and POC stocks are also a sensitive indicator to detect the short-management effects. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The knowledge of profile distribution of soil organic carbon (SOC) in long-term agricultural systems could help to store atmospheric carbon in the soil. We investigated profile distribution of easily oxidisable Walkley-Black SOC pool (SOCWB) under long-term rice-wheat (R-W) and maize-wheat (M-W) cropping systems under soils of different pedogenesis. The soil samples were collected from the characteristic genetic horizons and analysed for carbon fractions. The SOCWB was the highest in soils under R-W systems in both Alfisols and Inceptisols. The SOCWB stock in the deeper profile horizons under R-W system was significantly ( p < 0·05) higher than that under M-W system especially in Typic Hapludalfs. Long-term R-W system could store on average 3·55 Mg ha−1 more SOCWB than M-W system in the Ap horizon. The SOCWB stock in the Ap horizon of all pedons was significantly ( p < 0·05) higher in Alfisols than that in Inceptisols. About 60-90% of the total profile SOCWB stock was contributed by B-horizon because of its greater extent. Considering the whole profile, clay was negatively correlated with SOC fractions; however, the SOC fractions were closely related to each other. This study reveals that the distribution of SOCWB is different in long-term R-W and M-W systems not only in surface but also in the deeper horizons and the magnitude of the variation is influenced by the specific pedogenic processes. This indicates the significance of profile SOCWB stock instead of topsoil SOCWB stock in quantifying carbon retention potential of the long-term management practices. Copyright © 2014 John Wiley & Sons, Ltd. [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]

Accurate modelling of agricultural management impacts on greenhouse gas emissions and the cycling of carbon and nitrogen is complicated due to interactions between various processes and the disturbance caused by field management. In this study, a process-based model, the Soil-Plant-Atmosphere Continuum System (SPACSYS), was used to simulate the effects of different fertilisation regimes on crop yields, the dynamics of soil organic carbon (SOC) and total nitrogen (SN) stocks from 1990 to 2010, and soil CO 2 (2007–2010) and N 2 O (2007–2008) emissions based on a long-term fertilisation experiment with a winter-wheat ( Triticum Aestivum L.) and summer-maize ( Zea mays L.) intercropping system in Eutric Cambisol (FAO) soil in southern China. Three fertilisation treatments were 1) unfertilised (Control), 2) chemical nitrogen, phosphorus and potassium (NPK), and 3) NPK plus pig manure (NPKM). Statistical analyses indicated that the SPACSYS model can reasonably simulate the yields of wheat and maize, the evolution of SOC and SN stocks and soil CO 2 and N 2 O emissions. The simulations showed that the NPKM treatment had the highest values of crop yields, SOC and SN stocks, and soil CO 2 and N 2 O emissions were the lowest from the Control treatment. Furthermore, the simulated results showed that manure amendment along with chemical fertiliser applications led to both C (1017 ± 470 kg C ha −1 yr −1 ) and N gains (91.7 ± 15.1 kg N ha −1 yr −1 ) in the plant-soil system, while the Control treatment caused a slight loss in C and N. In conclusion, the SPACSYS model can accurately simulate the processes of C and N as affected by various fertilisation treatments in the red soil. Furthermore, application of chemical fertilisers plus manure could be a suitable management for ensuring crop yield and sustaining soil fertility in the red soil region, but the ratio of chemical fertilisers to manure should be optimized to reduce C and N losses to the environment. [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]

Crop residue burning is a major environmental issue and their potential long-term impact on the climate is a global concern. A laboratory experiment was carried out to study the impact of biochar on carbon loss from tropical soils. Residues of two important foodgrain crops viz, rice and wheat were used to prepare respective biochar and added as amendments in two different tropical agricultural soils (red and alluvial). In general carbon loss was more from alluvial soil than red soil. In alluvial soil, carbon loss was more when biochars were applied along with N fertilizer (urea) than biochar alone. Increasing rate of application of rice biochar without urea showed potential carbon protection in alluvial soil. Interestingly, unlike rest of the treatments, carbon loss was more in red soil when wheat biochar was applied without urea than with it. While physicochemical characteristics of biochars play crucial role in carbon protection, the intrinsic nature and properties of soil largely regulates it. © 2015 American Institute of Chemical Engineers Environ Prog, 35: 183-188, 2016 [ABSTRACT FROM AUTHOR]

Nitrogen fertilizer is the most commonly fertilizer for increasing grain yield of wheat, but its effects on wheat carbon (C), nitrogen (N) and phosphorus (P) availability are not clear yet. This field experiment was conducted to evaluate the C, N and P stoichiometry characteristics of winter wheat and soil and their relationship during the anthesis and harvest stages under nitrogen fertilization (0, 180, 360 kg ha-1) in Northwest China. We found that N fertilization could increase N contents, C: P and N: P ratios and decrease P contents, C: N ratio in wheat. During anthesis, the highest N and P contents were found in the flag leaf and culm, respectively and at harvest, N and P contents were higher in the grain. N and P contents in all tissues of wheat were related, and more importantly, a significant relationship with the soil N and P contents was found, these results could help us understand the nutritional balance regulation in wheat under nitrogen fertilization. © 2015 Friends Science Publishers [ABSTRACT FROM AUTHOR]

Introduction: 14th Line, "The variation between C3 (~ 27%) and C4 (~ 13%)"; Page no: 2, 1st line "ranging from - 23 - - 40% ... from - 9 to - 19%". 2nd page under title: Materials and methods (Soil sample and analysis): 15th line " SP 13 sp C3 and SP 13 sp C4 are - 27% and - 13%". [Extracted from the article]

The effect of conventional ploughing, mulching, and direct drilling on the soil organic C (soil Corg) contents through the soil profile and on total soil Corgstocks (0–45 cm) was investigated at five different German sites. All sites showed similar results: after 10–13 years, soil Corgcontents in the surface soil (0–10 cm) were 15–71% and 33–42% higher under direct drilling and mulching, respectively, than under ploughing (8–18 g kg−1). Under ploughing, the soil Corgcontents were distributed homogenously through the soil profile. Either mulching or direct drilling resulted in 3–28% higher soil Corgstocks than ploughing (49–116 t ha−1). However, the tillage management was no significant factor since the sites showed the effects to different extents but were the mathematical replications. Five to six years later, trends and values were similar. We concluded that the main effect of mulching or direct drilling was the stratification with higher soil Corgcontents in the surface soil. Since this is a positive means for soil protection, we suggested that the use of mulching or direct drilling can contribute to a sustainable soil management in crop rotations with sugar beet which are characterized by a strong physical impact on the soil during harvest. [ABSTRACT FROM PUBLISHER]

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]

The objective of this study was to investigate the effects of addition of pulses in crop sequences, crop residue management, and application of fertilizer N on soil nitrogen content, soil organic carbon, nutrient uptake, and its consequences for wheat yields. The field experiments were carried out from 2009 to 2012 in the sub-humid and sub-tropical zone of northern India. The treatments were (i) crop residue retained (+Residue) or (ii) removed (-Residue), (iii) 120 kg N ha-1 applied to wheat, (iv) 150 kg N ha-1 to maize, and (v) a control with no nitrogen applied to either wheat or maize. The cropping systems consisted of a rotation of wheat and maize or wheat and green gram. Postharvest incorporation of crop residues significantly (P< 0.05) increased the wheat grain and straw yields during 2010-2011 and 2011-2012. On average, crop residues incorporation increased the wheat grain yield by a factor of 1.31 and straw yield by 1.38. The wheat crop also responded strongly to the previous legume (green gram); grain yield increased by a factor of 1.89 and straw yield by 2.05, compared to the control. Application of fertilizer N to the preceding maize crop exerted a strong carryover effect on grain (1.18) and straw yield (1.26) wheat. Application of N fertilizer to wheat increased grain and straw yields by, respectively, a factor of 1.69 and 1.79 on average. The overall conclusion is that an improved crop residue management, combined with application of fertilizer N or incorporation of legumes greatly improves the N economy of cereal cropping systems and enhances crop productivity in soils with a low N content on the short term. [ABSTRACT FROM AUTHOR]

Biomass burning is a major contributor to the atmospheric carbon budget and increases the concentration of many trace gases apart from the adverse effects on soil properties. However, in many parts of India, crop residue burning is a recurrent and widespread practice for disposal of the residues after harvest of the previous crop to facilitate sowing of the succeeding crop. The residue burning on a larger scale also leads to severe atmospheric pollution. Against this backdrop, the present work was conducted to study the effect of wheat (Triticum aestivum) residue burning on soil properties and assess the potential greenhouse gas emission from burning of such residues on a regional scale. The study was taken up on farmers' field in Bhopal district, Madhya Pradesh, with two residue disposal methods, viz. residue burning and residue removal, for comparison with respect to their effect on soil properties and the greenhouse gas emission potential. No significant difference was observed between both methods in terms of soil organic carbon, inorganic carbon and available P content at 0-15 and 15-30 cm soil depths. Though residue burning showed favourable effect on available K content, there was reduction in the available N content in the 15-30 cm soil depth. Residue burning did not show significant effect on soil biological activity as estimated from fluorescence diacetate test. On the other hand, there was a significant adverse effect on soil structure and labile carbon content. Residue burning was estimated to result in the emission of 379 Gg C equivalent for India and 14 Gg C equivalent for MP. [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]

Background and Aims: Soil micro-circumstance and biological stress resistance were studied to validate our hypothesis that the allelopathic potential that was enhanced by breeding resulted partially from rhizophere microbes associated with the different varieties. Methods: The rhizosphere soils from four wheat genotypes with different allelopathic potential were collected so as to compare their soil micro-environments and bio-pressure tolerances. Results: The levels of these three categories such as bacteria, fungi, and actinomycetes ranged among 1.54-26.59 × 10, 0.43-4.12 × 10, and 1.36-18.25 × 10 CFU/g soil, respectively. Wheat 22 Xiaoyan with greater allelopathic potential had higher levels of microorganisms than the other three genotypes having weak allelopathy. The soil microbial carbon and nitrogen analyses suggested that wheat could create an active microhabitat with high activities of key soil enzymes such as urease, catalase, sucrase, and dehydrogenase. Using the approximate concentrations detected in wheat rhizosphere soils, the leachates of all four wheat materials significantly inhibited the growth of the weed Descurainia sophia and take-all pathogen Gaeumannomyces graminis var . Tritici. Conclusions: Wheat exudates provided carbon and nitrogen resources for the relevant microorganism. Meanwhile, the rhizosphere soil microbes contributed to allelopathic potential of wheat by positive feedback. [ABSTRACT FROM AUTHOR]

In this study, we performed a rhizobox experiment to examine the dynamic changes in the rhizosphere properties and antioxidant enzyme responses of Triticum aestivum L. under three levels of cadmium stress. A set of micro-techniques (i.e., Rhizobox and Rhizon SMS) were applied for the dynamically non-destructive collection of the rhizosphere soil solution to enable the observation at a high temporal resolution. The dynamics of soluble cadmium and dissolved organic carbon (DOC) in the rhizosphere soil solutions of the Triticum aestivum L. were characterised by the sequence week 0 after sowing (WAS0)<3 weeks after sowing (WAS3)<10 weeks after sowing (WAS10), whereas the soil solution pH was found to follow an opposite distribution pattern. Systematically, both superoxide dismutase (SOD) and catalase (CAT) activities in the leaves of the Triticum aestivum L. increased concomitantly with increasing cadmium levels (p>0.05) and growth duration (p<0.05), whilst ascorbate peroxidase (APX) activity was induced to an elevated level at moderate cadmium stress with a decrease at high cadmium stress (p>0.05). These results suggested the enhancement of DOC production and the greater antioxidant enzyme activities were two important protective mechanisms of Triticum aestivum L. under cadmium stress, whereas rhizosphere acidification might be an important mechanism for the mobilisation of soil cadmium. The results also revealed that plant–soil interactions strongly influence the soil solution chemistry in the rhizosphere of Triticum aestivum L., that, in turn, can stimulate chemical and biochemical responses in the plants. In most cases, these responses to cadmium stress were sensitive and might allow us to develop strategies for reducing the risks of the cadmium contamination to crop production. [Copyright &y& Elsevier]

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]

Tillage and crop residue inputs are important factors that impact soil aggregation and soil organic C (SOC) decomposition. This study evaluated the impacts of tillage and 10 yr of crop residue removal on aggregate stability, distribution, and associated C. The research was conducted in North China between 2002 and 2011. The treatment s were five tillage systems that included conventional tillage (CT), subsoiling (ST), harrow tillage (HT), rotary tillage (RT), and no-till (NT) in combination with crop residue retention (P) or residue removal (A). The results indicate that 74 to 82% of aggregates were macroaggregates (0.25-5 mm) and that these aggregates contained from 53 to 87% of the SOC in the 0- to 30-cm depth. Tillage and residue removal reduced macroaggregates and SOC levels, especially under the RT treatment, but residue inputs slowed down the rate of SOC depletion in the soil. The treatments of no-till with residue retention (NTP) and subsoiling with residue retention (STP), accumulated more C in stable macroaggregates and significantly increased SOC levels, which increased 13.37 and 9.59 Mg C ha-1, respectively, in 10 yr. Crop residue input combined with an appropriate tillage system is an effective method for maintaining and improving low-quality soil and SOC levels in the widespread wheat (Triticum aestivum L.)-maize (Zea mays L.) cropping system of North China. [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]

Soil turning during pre-seeding preparation is meant to loosen and promote physical characteristics responsible for the development of crop roots in soil. In this study, we demonstrate effects of three methods of pre-seeding preparation at two depths of irrigation on carbon dioxide (CO2) efflux as well as the temporal variability in the distribution of soil carbon. This experiment was conducted at the rural cooperative extension research station in Tangará da Serra, Mato Grosso, Brazil, for two wheat production years in 2011 and 2012. The experimental design was randomized in strips, with four repetitions. Wheat was irrigated during the June to early October dry season. The treatments include two methods of soil preparation: traditional preparation with one plowing and two disc harrowings and minimal preparation with one seed bed conditioner pass. A third treatment of direct seeding was also evaluated. Soil CO2 efflux, soil temperature, air-filled soil porosity, and labile carbon were measured. We found soil preparation affects CO2 efflux in irrigated cultivation systems within Brazil's Cerrado savannah, with conventional tillage having greater CO2 emissions than either reduced tillage or direct seeding. Soil CO2 emissions were lower at 508 mm versus 698 mm irrigation depth, but wheat yields were significantly lower. [ABSTRACT FROM AUTHOR]

Deforestation for agricultural development or extension is a common land-use problem that may cause a series of changes in the ecological environment and soil carbon stock in planting systems. However, the response of soil physical, chemical properties and carbon stocks in agricultural systems in the initial period after deforestation have not been thoroughly examined, especially in the subsoil. We investigated the variations in the soil physicochemical properties and organic carbon stocks to a depth of 100 cm in a poplar (Populus deltoides cv. 35) plantation, a summer maize (Zea mays L.) followed by winter wheat (Triticum aestivum L.) field after 1 year of deforestation of a poplar plantation, and a wheat–maize rotation field used for decades. The soil bulk density and pH decreased, and the soil total nitrogen (TN), total phosphorus, and total potassium contents increased considerably. The soil organic carbon (SOC) content and stocks (to 100 cm) increased by 32.8% and 20.1%, respectively. The soil TN content was significantly (p < 0.001) positively correlated with the SOC content, and the C:N ratio increased for the field following deforestation. Furthermore, the nitrogen in the poplar plantation and the field following deforestation was limited. We recommend increasing the amount of nitrogen fertilizer following deforestation to improve fertility and this will be beneficial to SOC storage. [ABSTRACT FROM AUTHOR]