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Biochar is a source of stable organic matter being explored as a manure additive. A 64 d incubation experiment was conducted to quantify the short-term effect of manure (RM), biochar–manure (BM), raw biochar (BC), RM + BC, and BM + BC amendment on soil carbon (C) and nitrogen (N) mineralization. Manure increased CO2-C emission rates, with the highest cumulative CO2-C emissions being observed for RM + BC. Treatments with BM halted soil C mineralization, indicating manure-C stabilization. By contrast, neither RM nor BM affected soil N mineralization. Applying BM might benefit soil C sequestration by lowering CO2-C emissions over the long term.

Soil hydraulic properties are important aspects of the bamboo plantation's eco-hydrological processes as they affect the runoff, soil erosion, and water balance. This study assessed the effect of four commercially important sympodial bamboo species viz., Bambusa vulgaris, Bambusa balcooa, Dendrocalamus hamiltonii, and Dendrocalamus strictus on surface soil saturated and near-saturated hydraulic conductivity (NSHC), macropore characteristics, and the factors influencing the soil hydrological processes. The surface soil hydraulic conductivity at 0, -10, and -30 mm pressure heads and macropore characteristics were estimated from measured steady-state infiltration using a tension (hood) infiltrometer. Soil organic carbon, bulk density, aggregate mean weight diameter (MWD), root biomass, and litterfall was correlated with saturated hydraulic conductivity (SHC) to determine these parameters' relationship with the hydraulic properties. D. hamiltonii showed significantly higher SHC, NSHC, and water-conducting macroporosity than the rest of the species. The correlation analysis revealed that root biomass and soil aggregate MWD were the major determinants of soil hydraulic conductivity characteristics. Bulk density, soil organic carbon, and leaf litter were weakly correlated with SHC. Among the species evaluated, D. hamiltonii was found to be a highly promising species for improvement of soil hydro-physical property and, therefore, can be recommended for increasing infiltration, reducing runoff, controlling soil erosion, and improving groundwater recharge.

To better understand interglacial paleosol development by quantifying the paleosol development processes on the Chinese Loess Plateau (CLP), we need a soil genesis model calibrated for long timescales. Here, we calibrate a process-based soil genesis model, SoilGen2, by confronting simulated and measured soil properties for the Holocene and MIS-13 paleosols formed in the CLP for various parameter settings. The calibration was made sequentially on three major soil process formulations, including decalcification, clay migration and soil organic carbon, which are represented by various process parameters. The order of the tuned parameters was based on sensitivity analyses performed previously on the loess in West European and the CLP. After the calibration of the intrinsic soil process parameters, the effect of uncertainty of dust deposition rate on calibration results was assessed. Our results show that the simulated soil properties are very sensitive to ten reconstructed dust deposition scenarios, reflecting the propagation of uncertainty of dust deposition in model simulations. Our results also show the equal importance of calibrating soil process parameters and defining correct external forcings in the future use of soil models. Our calibrated model allows interglacial soil simulation in the CLP over long timescales.

Some of the highest nitrous oxide (N2O) emissions arising from Australian agriculture have been recorded in the high-rainfall zone (>650mm) of south-western Victoria. Understanding the association between nitrogen (N) management, crop N uptake and gaseous losses is needed to reduce N2O losses. Field experiments studied the effect of N-fertiliser management on N2O emissions, crop N uptake and crop productivity at Hamilton and Tarrington in south-western Victoria. Management included five rates of urea-N fertiliser (0, 25, 50, 100 and 200kgN/ha) topdressed at either mid-tillering or first-node growth stages of wheat development; urea-N deep-banded 10cm below the seed at sowing; and urea coated with the nitrification inhibitor DMPP (3,4-dimethylpyrazole phosphate) was either topdressed or deep-banded. Pre-sowing soil profile chemical properties were determined before static chambers were installed to measure N2O losses, accompanied by wheat dry matter, crop N uptake and grain yield and quality, to measure treatment differences. N2O losses increased significantly (P≤0.10) where urea-N was deep-banded, resulting in a 2–2.5-fold increase in losses, compared with the nil N control. The high N2O losses from deep-banding N appeared to result from winter waterlogging triggering gaseous or drainage losses before wheat reached peak growth and demand for N in spring. Despite the high losses from deep-banding urea-N, grain yields were largely unaffected by N management, except at Hamilton in 2012, where topdressed wheat growing in a soil with large reserves of NO3–-N, and later experiencing post-anthesis water deficit resulted in a negative grain yield response. All sites had high concentrations of soil organic carbon (>2.8%) and the potential for large amounts of N mineralisation throughout the growing season to supplement low N fertiliser recovery. However, topdressed urea-N resulted in significant enrichment of crop tissue (P≤0.004) and associated positive response in grain protein compared with the deep banded and nil N treatments. 3,4-Dimethylpyrazole phosphate (DMPP)-coated urea provided no additional benefit to crop yield over conventional urea N. Our study highlighted the importance of synchronising N supply with peak crop N demand to encourage greater synthetic N uptake and mitigation of N2O losses.

In permafrost peatlands, the degradation of permafrost soil can raise soil temperature and alter moisture conditions, which increases the rate of loss of soil organic carbon (SOC). Here we selected three typical permafrost types that have very different active layer thicknesses but with soil originating from the same vegetation and which exist under comparable climatic conditions in the Da Xing’an mountain range: continuous permafrost, island permafrost, and island melting permafrost. To quantify the relative importance of control elements on SOC stabilization in these different permafrost types, we used correlation analysis to assess the relationship between organic carbon, physical and chemical properties and microorganisms, and explored the contribution of these factors to the accumulation of organic carbon. This study shows that the interaction between clay or silt, iron oxides and microorganisms have an important influence on the stability of organic carbon in permafrost peatlands.

Soil inorganic carbon (SIC) is an important reservoir of carbon (C) in arid, semi-arid, and semi-humid regions. However, knowledge is incomplete on the dynamics of SIC and its relationship with soil organic C (SOC) under different land use types in the semi-humid region, particularly in coastal zones impacted by soil salinization. We collected 170 soil samples from 34 profiles across various land use types (maize-wheat, cotton, paddy, and reed) in the middle-lower Yellow River Delta (YRD), China. We measured soil pH, electrical conductivity (EC), water-soluble salts, and SOC and SIC contents. Our results showed significant differences in both SOC and SIC among land use types. The dry cropland (maize-wheat and cotton) soils had significantly higher SOC and SIC densities (4.71 and 15.46 kg C m–2, respectively) than the paddy soils (3.28 and 14.09 kg C m–2, respectively) in the 0–100 cm layer. Compared with paddy soils, reed soils contained significantly higher SOC (4.68 kg C m–2) and similar SIC (15.02 kg C m–2) densities. There was a significant positive correlation between SOC and SIC densities over a 0–100 cm soil depth in dry cropland soils, but a negative relationship in the paddy soils. On average, SOC and SIC densities under maize-wheat cropping were 15% and 4% lower, respectively, in the salt-affected soils in the middle-lower YRD than the upper YRD. This study indicated that land use types had great influences on both SOC and SIC and their relationship, and salinization had adverse effect on soil C storage in the YRD.

Crested wheatgrass (CWG) [Agropyron cristatum (L.) Gaertn.] is a commonly introduced grass in the Canadian prairies, but concerns remain about its possible long-term effects on soil quality, and its influence on soil water repellency (SWR) has not been determined. The long-term (24 yr) effects of CWG on SWR in comparison to seeded native grasses and annual cropping were determined for a clay loam soil in southern Alberta, Canada by measuring SOC concentration and SWR using soil hydrophobicity (SH) and soil water repellency index (RI) methods. The cropping treatments were CWG, seeded native grass mix (NGM), continuous wheat, and wheat–fallow rotation, each with fertilized (nitrogen) and non-fertilized subplots, replicated four times. Mean SOC concentration, SH, and RI in samples of surface soil were similar (P > 0.05) for CWG and seeded NGM, and they did not support our hypothesis (seeded NGM > CWG). Mean SOC was significantly greater for seeded perennial grasses than annual crops by 1.7–2 times and SH by 2.1–2.5 times, which supported our hypothesis, but RI was similar among treatments. As expected, nitrogen fertilization significantly increased SOC concentrations, but the effects on SH and RI were undetectable. A strong positive correlation occurred between SOC concentration and SH (r = 0.92) but not for RI (r = 0.10). Our findings suggested that SWR was similar for CWG and seeded NGM. The SWR as measured using SH was greater for seeded perennial grasses than annual cropping but was similar using RI.

Context Sustainable management of the soil is one of the pillars of conservation agriculture (CA). Aims The objective of this study was to evaluate the long-term effects of soil management systems (SMS) on liming efficiency, soil chemical properties and wheat yield. Methods This study was part of a long-term experiment established in 1986 in Passo Fundo, Rio Grande do Sul, Brazil, but using data from 2008 to 2015 to explore the effects of agricultural lime applied in 2008. The experiment was laid out in a split-plot design where the main plot (SMS) were arranged in randomised blocks and the cropping systems (sub-plot treatments) were randomised within the main plots. This study assessed the effects of the SMS; i.e. two CA systems [no-tillage (NT) and reduced tillage] and two conventional tillage (CT) systems (disk ploughing + disk harrowing annually, and mouldboard ploughing + disk harrowing annually). Key results The NT system was the most sustainable due to improvements in soil organic carbon concentration. After liming, CT systems were more effective than CA systems in decreasing Al3+ toxicity and increasing soil pH and Ca2+ and Mg2+ concentrations at deeper soil layers. The NT system had a considerable advantage over other SMS, due to a greater average wheat yield (18%). Conclusions The SMS evaluated in this study modified chemical properties when compared with the native forest area. The NT system was the least detrimental to soil organic carbon, an important indicator of soil quality. Implications The NT system provided greater average wheat yield (18%), and thus was the most viable SMS for subtropical spring wheat production.

Soil aggregates store most soil organic carbon (SOC), but how does litter quality influence their formation? We hypothesized varying litter quality to facilitate differences in aggregate formation by altering the seasonal development of microbial biomass (MB) C and N, with MB driving aggregate development in a tropical sandy soil in Thailand. Aggregate development was studied in a long-term fallow experiment, receiving 10 Mg ha−1 annual applications of rice (Oryza sativa) straw (low N and polyphenols (PP)), groundnut (Arachis hypogaea) stover (high N, low PP), tamarind (Tamarindus indica) litter (medium N and PP), or dipterocarp (Dipterocarpus tuberculatus) leaf litter (low N, high PP) compared to a control. N-rich litter from groundnut and tamarind led to significantly higher MB, bulk soil C and aggregate C than dipterocarp, rice straw, and the control. Bulk soil C and small macroaggregates C of N-rich litter treatments increased about 7% in 30 weeks. Increasing MB N explained increasing small macroaggregate C and both, MB C or N were important covariates explaining temporal variations of C stored in themicroaggregates, in silt and clay. MB also explained temporal variations of aggregate fraction weights. With time, SMA C only increased in the N-rich groundnut and tamarind treatments, but decreased in other treatments. Connections of MB to aggregate C and weight substantiated the importance of microbial activity for aggregate formation and carbon sequestration. By promoting MB for longest time spans, medium-quality tamarind could best facilitateaggregate formation, and increase silt and clay C.

Context Compaction removal and organic amendment application are commonly used to mitigate the compaction-induced declines in crop yield, soil carbon (C) and soil health. However, the response of microbial activities and nutrient pools to the combination of mill-mud amendments and decompaction in the soil profile are not fully understood. Aims A field trial was conducted at Burdekin, Australia, to investigate the effects of different decompaction managements on soil nutrient cycling, associated biological activities and sugarcane yield. Methods This experiment included four treatments: control (CK, without mill-mud), mill-mud shallow furrow (MS), deep trenching without mill-mud (DT) and deep trenching mill-mud application (MD). Key results The MD treatment increased concentrations of hot water extractable organic C by 30–70% and hot water extractable total nitrogen (N) by 30–90% at the application depth. Soil microbial biomass C and N were also higher in mill-mud applied layers. Mill-mud applied treatments increased plant cane yield by 7% (MS treatment) and 14% (MD treatment) compared to CK. The DT treatment also increased plant cane yield by 11% compared to CK. Conclusion The MD treatment increased the supply of organic C and nutrients to the microbial community within the entire soil profile, enhanced nutrient cycling processes, improved soil environmental conditions and soil health for sugarcane growth and thus increased sugarcane productivity. Implications Further research should focus on microbial community composition shifts to further explore the mechanisms responsible for soil microorganism regulation of nutrient cycling in sugarcane farming systems.

Context Organic farming is based on the non-use of synthetic fertilisers and pesticides. Nitrogen inputs are derived from symbiotic fixation and organic fertilisers, which also contribute carbon to the agroecosystem. Soil organic carbon (SOC) generally increases in organically managed soils, but it is unclear whether the increase is due to carbon transfer from off-site or can be achieved without carbon transfer from other production systems. Aims This study aims to determine how carbon transfer is achieved to increase SOC under organic farming systems. Methods A meta-analysis was conducted to answer this question using articles published in peer-reviewed journals in which the results of randomised and replicated experiments were available. Data were collected from 66 experiments that generated 83 direct comparisons of organic vs conventional management. The data were divided into three groups: no carbon transfer between agroecosystems (no off-site effects, n = 15), with carbon transfer (off-site effects, n = 43), and undefined carbon management (n = 25). The response ratio was used as the effect size and the 95% confidence interval was calculated. Key results In experiments with no off-site effects, SOC did not differ between organic and conventional systems. In contrast, in experiments where manure-compost was transferred to organic systems from off-site or crop residues were harvested in conventional treatment, SOC was 22% higher in organic system. Conclusions These results indicate that organic farming increases SOC only when carbon is transferred between agroecosystems. Implications Off-site effects should be considered when addressing the carbon sequestration potential of organic farming.

For sustaining productivity and increasing biodiversity in Cox´s Bazar, a coastal area, and Bandarban, a hilly area, in Bangladesh, it is important to study the soil properties of the homegardens in these districts. We assessed the effects of varying forest management on soil carbon (C), nitrogen (N), and nutrients (P, K, Na, and Ca) between the hill and coastal homegardens. Soil samples were collected from 24 homegardens; 12 from the hill and 12 from the coastal sites. In both homegardens, the topsoil C and N stocks were up to 23% and 41%, respectively, higher than those in the deepest soil. We found a vertical decrease in C:N ratio in the soil of both homegardens, and the highest C:N ratios and C stock (49.90 Mg ha−1) were in the hill homegardens. The topsoil C in the hill homegardens was higher most probably due to higher deposition of litterfall and/or lower litter harvesting or mulching. The highest total N stock (5.97 Mg ha−1) was in the coastal homegardens, which may be due to higher tree density and species composition. The concentration and stocks of nutrients decreased vertically in the soil and this decrease was higher in the hill than in the coastal homegardens (except for P). It could be concluded that overall nutrient dynamics may be significantly affected by litter deposition, stand structure, and the variation in the rainfall. Soil N and nutrient deficiency should be considered in the planning of sustainable forest management to sustain productivity and increase biodiversity.

Context Gravel is a common constituent in soil and is routinely excluded when estimating soil carbon (C) and nitrogen (N) stocks. Aims We investigated the contribution that the gravel fraction (>2 mm) makes to C and N stocks in an agricultural soil. Methods The amount of gravel and the C and N content of gravel-associated organic matter (OM) was assessed to 180 cm in a long-term cropping soil with differing nutrient treatments. Key results Gravel-associated C and N accounted for ∼5% of the total C and N stocks in the upper layers (0–30 cm) of soil and up to 40% below 100 cm. The C:N ratio of the gravel-associated OM was similar to that in fine earth fraction (FEF) soil, with C:N ratio of ∼13 in surface layers to ∼8 at depth. Conclusions We estimated that 19% and 23% of the total stock of C and N, respectively, were associated with gravel over the whole soil profile. In the two nutrient treatments, with differing C and N stocks in the FEF, gravel-associated OM accounted for 9.3–10.6 t C ha−1 and 1.1–1.3 t N ha−1. Implications Our work highlights the significance of gravel in contributing to soil OM and the importance of sampling to depth to estimate soil C and N stocks. Importantly, disregard of the gravel fraction results in an underestimation of total soil C and N, which has implications for the accounting of C in agricultural soils and for the development of strategies to sequester soil C.

A large-scale ecological restoration project was initiated in the 1990s in southwest China, which is one of the largest areas of rocky desertification globally. However, the influence and potential mechanisms of vegetation restoration on soil carbon(C) sequestration in karst and non-karst regions remains unclear. Based on field investigation and multi-source data synthesis, the mechanisms of soil C sequestration were investigated to determine the most important variables affecting the rate of soil C change (Rs) in southwest China. Our results show significant differences in soil C sequestration between karst and non-karst regions with faster and longer C sequestration occurring in karst regions. In these areas, Rs was approximately 31% higher than in non-karst soils. The Rs of shrubland, grassland and cropland sites in karst areas was significantly higher than that observed in non-karst areas. We found that temperatures were the primary factor inhibiting soil C sequestration instead of precipitation. The total effect of nitrogen (N) on Rs was positive in both karst and non-karst regions. Phosphorus was the dominant factor limiting the use of N by vegetation in karst regions and then resulting in limitation of C sequestration. The results indicated that soil C storage may increase intermittently due to combination of karst environment and climate change in southwest China in future.

Context Tillage has temporal effects on soil organic matter and microbial attributes. Aim Three tillage systems (NT, no-tillage; MT, mulch tillage; MP, mouldboard ploughing) were used to assess the impact on soil quality indicators such as gravimetric soil water content (GSWC), soil organic carbon (SOC), total nitrogen (TN), easily extractable-glomalin (G EE), dehydrogenase (DHA), β-glucosidase (β-glu), urease (URE), acid-(AcP) and alkaline-(AlP) phosphatase over time in a sandy-loam Plinthustalf cropped annually with winter wheat and occasionally oat in eastern Free State. Methods Samples were collected during oat (October 2010, November 2010), fallow (February 2011, April 2011, May 2011) and wheat (August 2011, September 2011, October 2011) phases at 0–5 and 5–10 cm depth. Results When averaged over sampling dates, GSWC, SOC, TN and enzyme activities were 6–85% higher under NT than in MT and MP in the upper 5 cm soil. Trends changed at the 5–10 cm depth, with 20–32% higher enzyme activities recorded under MT. Soil quality indicators exhibited different trends over time, with GSWC, TN, DHA, AcP and AlP generally increasing during the fallow period and decreasing during oat and wheat phases, while β-glu was higher during both crop phases than at fallowing. URE was 33.6–174.3% higher during the oat phase than at the fallow and wheat phases. The opposite was observed with SOC, C/N ratio and G EE. Conclusions Enzyme activities were sensitive indicators, but SOC and TN can be used to assess temporal changes in soil quality in resource-limited countries. Implications However, temporal effects on SOC and TN were probably built in the long-term, hence further research focusing on multiple seasons is required.

Context Although both plant cover and mulch are considered for erosion control in arid and semi-arid regions, they have divergent impacts on soil ecology. Aim We examined the effects of orchard floor management practices on the density and diversity of soil free-living nematode communities and relevant soil abiotic properties. Methods Soils were sampled in winter in a citrus orchard in the Sharon region of Israel from plots that for 6 years had been under (1) annual native species; or (2) Avena sativa and Vicia villosa, planted between tree rows; or (3) woodchip mulching along tree rows. There were two control sites: (4) bare soil between tree rows and (5) bare soil along the tree rows (both common practice). Key results Nematode communities and their trophic diversity were significantly impacted by floor management. Significant increases in soil moisture under plant cover, and higher organic matter and water-holding capacity for all covered orchard floors could be related to nematode changes. Shifts in nematode feeding group structure suggest a shift in the type and availability of soil carbon pools. Conclusions There was a strong association between orchard floor management and soil free-living nematode communities, indicating a shift in the soil food-web structure and functionality. Bare soil harboured fewer nematodes, but more complex communities dominated by persisters, while seeded plant cover had a greater nematode abundance dominated by coloniser communities, indicating increased availability of resources. Implications Results reveal the importance of integrating biological information in performance index determinations for improving soil management decisions, suggesting these relationships as sensitive bio-indicators of soil health.

The purpose of this study is to assess the individual and interactive effects of different rates of rice straw incorporation, Rsti, (0, 5, 7.5, and 10 t ha−1) and nitrogen fertilizer, N, (0, 90, 120, and 150 kg ha−1) on changes in physicochemical properties, available nutrients of surface soil, and wheat yield in a long-term rice-wheat system field experiment. Following rice in wheat crop, four rates of Rsti in the main plots and four rates of N in the sub plots were applied in a split-plot design with three replications. After wheat harvest of the 10th rice-wheat cropping cycle, triplicate soil samples were collected from 0 to 15 cm soil layer. Rice straw incorporation improved the soil organic carbon, soil aggregation, porosity, retention, and availability of water, as well as macro and micronutrients availability, and reduced resistance to root penetration, but increased soil bulk density. Wheat yield increased up to 7.5 t ha−1 Rsti and N up to 120 kg N ha−1. Among the assessed soil properties and available nutrients influenced by Rsti and N, supplementary soil organic carbon and available potassium were the top-ranked soil properties responsible for increased wheat yield. Wheat yield increased with rice straw incorporation was mainly due to increased soil organic carbon and available potassium.

The priming effect (PE) on native soil organic matter induced by exogenous carbon addition influences soil carbon and nutrient cycling across the soil depths. Therefore, this study aimed to explore the effects of exogenous glucose-induced PE on native soil organic carbon (SOC) influenced by soil properties across soil depths, weather factors in different ecosystems and experimental variables. We conducted a meta-analysis of 1231 experimental comparisons from 41 publications to explore the responses of native SOC to stable or radioactive carbon isotope (glucose) addition in laboratory incubation experiments representing various ecosystems and soil depths on the global scale. Overall, glucose addition had 110% positive PE on native SOC. The PE was higher in deep soil (197%) and lowest in topsoil (99%). Deep soil contains significantly lower SOC, dissolved organic carbon and microbial biomass carbon and a higher soil carbon/nitrogen ratio than topsoil. The PE positively correlated with soil carbon/nitrogen ratio and glucose addition rate but negatively correlated with microbial biomass carbon, dissolved organic carbon, SOC and incubation duration. Furthermore, PE positively related to mean annual temperature and precipitation in cropland while negatively correlated with mean annual precipitation in grassland ecosystem. Low soil nutrients and high carbon/nitrogen ratio is the reason for higher PE in deep soil than topsoil. Furthermore, the experimental variables and weather factors provide a framework for understanding the magnitude and direction of PE on native SOC induced by glucose addition and highlight the need for future integrated approaches of studies on PE.

The soil carbon (C) and nitrogen (N) dynamic was usually considered as a minor change based on a static process in the sealed soil under decades of impervious surface (IS). However, no systematic studies concerning the soil organic carbon (SOC) and nitrogen (SON) dynamic were conducted under IS in contrast with urban vegetation (i.e., forest, grass). Here we utilized fractional distillation of soils as well as stable isotopic analysis to examine soil C&N cycles after 20 and 30 years of vegetation planting and IS construction in Guangzhou and Shenzhen, Pearl River Delta, China. Soil samples including bare soil (CK) and four land use treatments were split into different chemical fractions. Then we analyzed the C&N content, C/N ratio, δ13C, δ15N, C&N recalcitrant indices (RIC, RIN), and the mean residence time (MRT). We found that the soil C&N increased first (i.e., 20 years) because of enhanced C&N stocks in both labile (LP) and recalcitrant pool (RP), and then stabilized or decreased (i.e., 30 years) with the IS ages in both cities. IS had a lower SOC decomposition rate and thus resulted in the five to ten times longer MRT (about 259–465 years) than that in vegetated soils (about 39–55 years). Moreover, the SOC&SON always showed a decoupling relation in labile pools (i.e., LC and LN) in forests in both cities. The study showed the IS remarkably altered the soil C&N dynamics, showing a great difference in SOC&SON fractions composition and turnover compared with vegetation.

A study was conducted to examine changes in soil fertility under different fallow periods in fields of smallholder farmers under contrasting soils and agro-ecologies in North West Zimbabwe. The study was a 4*4*6 factorial design replicated three times consisting three factors namely agro-ecological region (AER) (II, III, IV, V), soil texture (sandy clay loam, sandy loam, loamy sand and sand) and fallowing period in years (0–5, 6–10, 11–15, 16–20 and two controls). Soil samples were analysed for pH, soil organic carbon (SOC), soil KCl-extractable nitrogen (N), bicarbonate-extractable phosphorus (P) and exchangeable potassium (K) using standard methods. There was no significant three-way interaction (p > 0.05) among AER, soil texture and the fallow period on the soil fertility properties except for soil pH. Soil KCl-extractable N was significantly influenced (p

The rhizosphere and root detritusphere are hotspots of microbial activity, where root-derived inputs induce intensive priming effects (PE) on soil organic carbon (SOC) decomposition. These conditions for induced PE differ between rhizosphere and detritusphere and are modified by plant traits. Continuous labelling with 13C-depleted CO2 allowed for the partitioning of plant and soil C sources of CO2 efflux and the investigation of the PE in the rhizosphere and detritusphere of slow-growing conservative Carex acuta and fast-growing acquisitive Glyceria maxima. Glyceria allocated more C into the soil, induced higher microbial activity and a larger portion of active microorganisms, and depleted mineral N stronger than Carex. Its rhizosphere PE was 2.5 times stronger than that of Carex. Root residues (detritusphere) induced negative PE at the early stage of decomposition (1–9 months). The depletion of available organic substances in the detritusphere of more easily decomposable Glyceria roots resulted in positive PE after 3 months. The PE in the detritusphere of N-poorer Carex roots was more intensive but started after 9 months. The rhizosphere PE was positive and stronger than the detritusphere PE, which switched from initially negative to positive PE after depletion of available substances during few months. More productive species with faster N-uptake and higher belowground C input (here Glyceria) induce larger rhizosphere PE than slower-growing species (here Carex). The N-rich Glyceria roots decompose faster than N-poor roots of Carex and, consequently, have a lower impact on SOC dynamics and induced a smaller positive detritusphere PE.

Context Success of the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) is dependent on a range of soil factors including pH and soil organic carbon (OC) content. Aims This study identified the effect of soil properties and moisture content at the time of DMPP application on the efficiency of DMPP and soil mineral N concentrations. Methods Soil was collected from paired paddocks with contrasting management, cropping or pasture across three sites. Soil samples were pre-incubated for 7 days with moist (−85 kPa) or air dried soil to simulate sowing into soil with moisture equivalents of post seasonal break or dry sowing. Urea ammonium nitrate (UAN) was applied with and without DMPP to all soils. Key results DMPP inhibited nitrification in all soils, although decreased inhibitory effectiveness was observed in acidic soils compared to neutral soils. Inhibition efficacy on acidic soils was improved when DMPP was applied to dry rather than wet soils. Neutral soils did not observe the same soil moisture effect having similar inhibition efficiency of DMPP observed between dry and wet soil application. Nitrogen fertilisers applied to dry soils nitrified at a greater rate than when applied to wet soils. DMPP decreased the ammonia oxidising bacteria (AOB) population while the ammonia oxidising archaea (AOA) amoA gene copy numbers were unaffected. Conclusions This study shows that the lower soil pH and high OC contents can reduce the efficacy of DMPP. Implications When using DMPP in Australian broad acre agriculture, knowledge of soil properties including soil pH will determine if application of DMPP is suitable for use before or after a seasonal break rainfall event.

Drought significantly impacts ecosystem structure and function, especially the transformation rates of soil carbon and nitrogen. This study explores how drought affects ecosystem respiration (R-e), methane (CH4) uptake and nitrous oxide (N2O) emissions in temperate desert steppes and the underlying mechanisms. Methods An in-situ experiment was conducted in the Inner Mongolia desert steppe in northern China to study the effect of drought on R-e, CH4 and N2O fluxes. Structural equation modeling (SEM) was used to establish the relationship between R-e, CH4 uptake and N2O emissions and plant functional traits and environmental factors. Results Ecosystem respiration and CH4 uptake were both significantly reduced by chronic drought (66 % precipitation reduction from 1 May to 31 August) but not by pulse drought (100 % precipitation reduction in June and July). In contrast, no significant impact on N2O emissions was observed under chronic or pulse drought. There were no significant direct effects of soil moisture on R-e, CH4 uptake or N2O emissions. However, soil moisture had an important indirect effect on R-e, CH4 uptake and N2O emissions, mainly through its influence on plant functional traits, plant above-ground biomass and soil nutrients. Plant biomass and soil temperature were the key indicators of R-e, and plant leaf nitrogen content was the key plant trait associated with N2O emissions. In contrast, plant specific leaf area and biomass were the key traits associated with CH4 uptake. Conclusions Overall, R-e and CH4 uptake were reduced by chronic drought in this desert steppe, but there was no significant effect on N2O emissions. Ecosystem respiration, CH4 uptake and N2O emissions were associated with plant functional traits. This provides new insight for the understanding of soil carbon and nitrogen dynamics in desert steppe systems under drought conditions and an important theoretical basis for the revision of model parameters.

We investigated the effect of Serendipita indica, an endophytic fungus, inoculation of different wheat (Triticum aestivum) cultivars on the rhizosphere physical quality. S. indica inoculated and uninoculated seedlings of wheat cultivars (Roshan, Ghods, Kavir and Pishtaz) were grown in rhizoboxes. Plants were harvested and intact samples were taken from the rhizosphere to measure soil organic carbon (SOC), hot-water soluble carbohydrates (HWSC), carbon mineralization rate (CMR), water repellency index (RI) by the sorptivity method, and aggregate stability by the high energy moisture characteristic (HEMC) method. Root mucilages of inoculated and uninoculated seedlings were also collected for measuring total polysaccharides (TPmucilage). The SOC, HWSC, and RI were increased by 146, 83, and 40% and CMR was decreased by 56% in planted treatments, which consequently increased the HEMC aggregate stability indices. S. indica increased SOC, HWSC, RI, and structural stability, and improved the physical quality especially in soil with Roshan and Ghods, which had more extensive root distributions and higher TPmucilage. The changes of soil-physical and hydraulic properties among different wheat cultivars imply that both quantitative and qualitative properties of root exudates have significant effects on soil quality. Soil with Roshan had the highest SOC, HWSC, and root distribution and the lowest aggregate stability. However, soil with Ghods had almost the same SOC and HWSC, but it had the highest stability indices. S. indica inoculation of different wheat cultivars, by increasing SOC and inducing water repellency in the rhizosphere, can improve the aggregate stability and soil physical quality.

The injection of pig slurry in the soil, associated with the no-tillage system and the reduction of carbon and nitrogen losses through volatilisation, can positively influence the carbon and nitrogen contents in the soil organic matter (SOM) fractions. The objective of the present study was to evaluate the effect of surface and injected applications of pig slurry to soils under a no-tillage system on soil organic carbon (SOC) and soil total nitrogen (STN) contents in particle-size fractions of the SOM. The no-tillage system included a crop rotation with grass species, summer maize, and winter black oat and wheat grown from 2011 to 2015. The treatments consisted of injected application of pig slurry, surface applications of pig slurry, application of chemical fertiliser (NPK), and a control with no soil fertiliser application. The 0–5, 5–10, and 10–20 cm soil layers were evaluated for SOC and STN contents, and for particle-size fractions: particulate organic carbon, particulate organic nitrogen, mineral-associated organic carbon, and mineral-associated organic nitrogen. We also evaluated the carbon and nitrogen contents and mass in the light organic matter. The injection of pig slurry increased carbon and nitrogen contents of all SOM fractions compared to surface application of pig slurry. These results suggest that the use of injected pig slurry to the soil under crop rotation in no-tillage reduces carbon and nitrogen losses by volatilisation and emissions to the atmosphere. We recommend the application of pig slurry by injecting in soil because it promotes higher increases in the SOM fractions. This form of application of pig slurry to the soil was shown as an effective and environmentally sustainable method for the conservation and improvement of soil quality.

Research carried out on soil organic carbon stock (SOCS) in the Sudano-Sahelian region of Cameroon is very rare. The few existing studies are mostly available in reports and concern in most cases carbon stocks in plant biomass. In order to contribute to the documentation on soils in this part of the country, the present work was designed to evaluate the SOCS in the main soil types and the influence of environmental factors and soil properties on these stocks under the natural dry tropical area of the Sudano-Sahelian zone of Cameroon. The study was undertaken in four sites, including three natural forest reserves (Laf, Zamai, Kosohon) and one national park (Mozogo), located at different latitudes. Three replicates were collected at each site, giving rise to three sampling points chosen per site, from 0 to 75 cm depth, for the determination of SOCS. At each sampling point, soils were sampled using depth increments of 25 cm from the surface. The studied area is covered by Haplic Vertisols, Dystric Arenosols, Dystric Leptosols and Dystric Planosols. Total SOCS (T-SOCS) content, which refers to a depth of 75 cm, decreases with increasing latitude, with 249±26.26 Mg ha−1 in Vertisols at Laf forest reserve most southerly located, 199±8.00 Mg ha−1 in Arenosols at Zamai forest reserve, 166±16.63 Mg ha−1 in Leptosols at Kosohon forest reserve and 161±8.88 Mg ha−1 in Planosols at Mozogo national park most northerly located, regardless of the altitude. No significant correlation was noted between T-SOCS and the altitude. A good correlation was noted between precipitation which decreases with increasing latitude and T-SOCS, indicating the importance of climate in the distribution of T-SOCS in the study area, which directly influences the productivity of the vegetation. More than 60 % of the SOCS was stored below the first 25 cm from the soil surface, a peculiarity of SOCS in drylands. The SOCS in the Sudano-Sahelian area of Cameroon is mainly influenced by climate and vegetation.

In Canterbury, New Zealand, there has been widespread conversion of dryland sheep grazing to more intensive irrigated dairying. We determined the effects of these land uses on soil carbon on a cent...

Urban soils are of increasing interest for their potential to provide ecosystem services such as carbon storage and nutrient cycling. Despite this, there is limited knowledge on how soil sealing with impervious surfaces, a common disturbance in urban environments, affects these important ecosystem services. In this paper, we investigate the effect of soil sealing on soil properties, soil carbon and soil nutrient stocks. We undertook a comparative survey of sealed and unsealed green space soils across the UK city of Manchester. Our results reveal that the context of urban soil and the anthropogenic artefacts added to soil have a great influence on soil properties and functions. In general, sealing reduced soil carbon and nutrient stocks compared to green space soil; however, where there were anthropogenic additions of organic and mineral artefacts, this led to increases in soil carbon and nitrate content. Anthropogenic additions led to carbon stocks equivalent to or larger than those in green spaces; this was likely a result of charcoal additions, leading to carbon stores with long residence times. This suggests that in areas with an industrial past, anthropogenic additions can lead to a legacy carbon store in urban soil and make important contributions to urban soil carbon budgets. These findings shed light on the heterogeneity of urban sealed soil and the influence of anthropogenic artefacts on soil functions. Our research highlights the need to gain a further understanding of urban soil processes, in both sealed and unsealed soils, and of the influence and legacy of anthropogenic additions for soil functions and important ecosystem services.

We checked the effect of biochar addition to a fertile temperate soil on plant growth and the quantity and quality of seeds of four varieties of wheat (Triticum spp., two “ancient” varieties, Verna and Senatore Cappelli, and two “modern” varieties, Bologna and Claudio) and a high oleic hybrid of sunflower (Helianthus annuus L.). Relatively novel is the qualitative investigation of the marketable product, as few are the works on this topic. We tested three different doses of biochar—1, 4, and 20 t ha−1—versus an untreated soil (“control”) in a 2-year open field trial in Central Italy, where wheat was grown the first year and sunflower the second year. Biochar addition did not change the soil characteristics save for the carbon content, which increased significantly with the highest dose of biochar. Also, we did not find any significant biochar-induced effect on plant growth and yields of both wheat and sunflower. Regarding the qualitative aspects, adding biochar to the soil implied an increase in total polyphenols in the middlings and bran of wheat and, with the highest dose of biochar, also in total proteins and in flavonoids and caffeic acid derivatives. Instead, no difference in carotenoids concentration and antiradical activity was observed in middlings or bran. As for the sunflower, no significant difference in seeds’ composition was detected at any of the biochar doses. The addition of biochar to a fertile, well-drained soil as the one we investigated is not detrimental to the quantity and quality of wheat and sunflower seeds. Rather, the concentration of some polyphenols in wheat appears to be positively affected by biochar addition., The work benefited of a doctoral fellowship (XXXIII cycle) by the University of Firenze. Marco Panettieri acknowledges the Spanish Ministry of Science, Innovation and Universities for his post-doctoral fellowship number IJCI-2016-27693. The formerly Spanish Ministry of Economy, Industry and Competitiveness (MINEICO) and AEI/FEDER are thanked for funding the project CGL2015-64811-P.