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Organic manure is considered as a beneficial fertilizer on soil quality and an excellent alternative resource of chemical fertilizer (CF). However, organic manure from intensive farms may have a negative impact on soil quality because of containing some harmful components, such as heavy metal and antibiotics. The aim of this study was to determine the influence of poultry litter (PL) and livestock manure (LM) from intensive farming on soil physical and biological indicators of soil quality. Results showed that PL and LM amendment increased soil macropore and mesopore volumes and decreased soil micropore volumes. Tensile strength in PL and LM treatment were lower than those in CF, while soil aggregate wet stability index were greater than those in CF. Compared with CF treatment, the microbial biomass C and N contents (+89%, +74%), soil basal respiration rate (+49%) and soil microbial quotient (+45%) in PL and LM treatment were significantly greater. Significant linear correlations were found between soil organic carbon and most soil physical and biological properties (P < 0.01). The results suggested that modern intensive farm manures can be alternate chemical fertilizers as a main fertilizer to improve soil physical and biological indicators in a rice-wheat system.

The work deals with the qualitative modifications of a Calcaric fluvisol after irrigation with fresh water and depurated pig-slurry effluents (aerobic and anaerobic treatment, and phytodepuration with a reed bed system). The accumulation of nutrients (nitrogen and phosphorus) and heavy metals (Cd, Co, Cr, Cu, Ni, Pb, Zn) as total and as bio-available forms in the soil was evaluated, together with soil aggregate stability index, hydraulic conductivity of the saturated soil and the in situ infiltration rate. The experimental field was divided into three plots, and cultivated with silage maize for three years (2003-2005). Results showed that the irrigation with depurated and phytodepurated effluents produced significant changes in the soil chemical properties controlling soil permeability, and influenced the bio-available fraction of heavy metals.

Aggregate stability (AS) is a key property in the soil system and it has been previously observed that its response to the fire can be very different with patterns that can show opposite trends depending on the principal cementing agents that control the aggregation between particles. In the case of some Mediterranean soils, previous studies observed an increase of AS. However it is not clear if this increase is real or apparent since fire could destroy a part of the aggregates and, therefore, what we are measuring is the AS that remains after fire. Soils from five different areas were heated in a muffle furnace at different temperatures (300, 500 and 700 °C) for 20 min. The weight of aggregate size fractions of 0.25–4 mm and < 0.25 mm before and after heating treatments was quantified. The loss of weight by the combustion, the organic matter content and AS were also measured in all samples studied. A selection of aggregates of the three studied soils (control and heated at 700 °C) were also analysed by X-ray diffraction (XRD) and the surface soils were observed by scanning electron microscopy (SEM-EDX), in order to identify mineralogical and structural changes in the surface of aggregates due to heating. Results showed an initial decrease in the proportion of the macro-aggregates at 300 °C with regard to control (unheated) samples for all the soils analysed ( p < 0.05). We presumed it is mainly due to the loss of SOM by combustion and subsequent disruption of some aggregates in lower sizes. However, this effect was not enhanced by heating the soils at 500 and 700 °C compared to 300 °C for any soil studied. Moreover, the heating treatments caused an increase in AS with heating temperature, despite no significant decrease for 0.25–4 mm aggregate fraction and the decrease of SOM produced by the combustion. Therefore, these results are not apparent as a consequence of the selection of the most resistant aggregates because of the destruction of other soil aggregates. X-Ray diffraction patterns and SEM-EDX analyses results in selected aggregates assisted us to explain the above-mentioned results of the increase of AS with heating temperature. The relative mineral abundances of the heated aggregates at 700 °C were slightly modified with regard to control. We observed some changes in the iron (hydr)oxides minerals, where the intensities had decreased and dehydroxylated to form maghemite. The presented results also show the disappearance of kaolinite for one of the soils. An increase of relative content of dolomite and calcite was also observed in the other two soils. In general, changes in compactness of soil micro-fabric units that have been produced as the consequence of the recrystallizations and micro-structural modifications observed by SEM-EDX in the surface of the soil aggregates after heating. These changes in cementing minerals may lead to a stabilization of the aggregate structure and hence an increase in the AS. [ABSTRACT FROM AUTHOR]

A growing body of research into the effects of biochar on soil physical characteristics suggests that it is most effective in coarse-textured soils. In this study, we set out to test this theory by comparing the effects of a woodchip biochar on a Chernozem, Cambisol and a coarse-textured Planosol in a pot experiment. We also compared the effect of different biochars on the Planosol, including woodchip biochar, straw biochar, and two vineyard-pruning biochars produced at different pyrolysis temperatures. Three characteristics were measured as indicators of good soil structure: bulk density, soil aggregate stability and plant available water. The woodchip biochar induced greater decreases in bulk density in the coarse textured Planosol than in the other soils. It also had a greater effect on soil aggregate stability in the Planosol than in the Cambisol, but had no effect on the Chernozem. Woodchip biochar had no effect on plant available water in any of the three soils. Straw biochar was the most effective at improving soil aggregate stability in the coarse-textured Planosol, with a 98% increase. Straw biochar also improved plant available water in the Planosol by 38% relative to the control, compared with 24% and 21% increases in the vineyard-pruning biochars, produced at 525 °C and 400 °C, respectively. Our study supports the theory that coarse-textured soils have the most to gain structurally from biochar amendments. We also show that straw biochar was the most effective at improving soil aggregate stability and plant available water in a coarse-textured Planosol. [ABSTRACT FROM AUTHOR]

We have developed a new methodology for the assessment of soil slaking under fast wetting conditions. We applied an image recognition algorithm to a set of digital images of soil aggregates immersed in water taken at regular time intervals. The kinetics of the slaking process was captured by measuring the projected aggregate’s area change over time. The methodology was tested in a dataset covering a great part of the agro-ecological variability of New South Wales (NSW), Australia. An empirical model which captures the rapid and slow slaking process was fitted to the data and three new slaking coefficients ( a , b and c ) were obtained and related to selected soil properties and land-use. The coefficient a , equivalent to the maximum slaking potential of the samples, was linearly related to exchangeable sodium, pH, clay percentage, calcium/magnesium and total carbon/nitrogen, and non-linearly related to total carbon. The coefficients b and c , equivalent with the initial slaking and the rate of change respectively, were found to be linearly related to nitrogen and total carbon. The coefficient a , was significantly lower in the natural sites reflecting a higher aggregate stability in those soils. The methodology is fast, inexpensive and simple; furthermore, it provides a new perspective in soil aggregate stability experiments, since it considers the slaking dynamics during the entire disaggregation process. [ABSTRACT FROM AUTHOR]

Soil water movement is closely related to soil tillage. However, the development of a solid understanding of the physical mechanism by which soil ionic composition influences soil water movement remains a challenge for the scientific community. In this study, the specific ion effects of Li + , Na + and K + on soil water movement in a permanently charged soil were examined, and the vertical infiltration experiment was employed. The results provided evidence of strong specific ion effects, for which cationic polarization appears to be responsible. The velocity of the wetting front in the presence of K + was up to 18.0 and 1.52 times faster than that in the presence of Li + and Na + , respectively; the water diffusion coefficient values in the presence of K + were up to 2300 and 9.451 times higher than those in the presence of Li + and Na + , respectively. At electrolyte concentrations ≤0.01 mol L −1 , water could not infiltrate into the soil in the presence of Li + . Knowledge of the interaction forces of soil particles combined with the experimental results on soil water movement indicates that the specific ion effects can be explained by cationic polarization. We concluded that the different polarizabilities among the three cations resulted in different soil electric field strengths for a given soil under a given electrolyte concentration, which led to differences in soil pore and aggregate stability, and thus differences in the soil water movement. Our results imply that it may be possible to regulate soil water movement by adjusting ionic polarization in a soil. [ABSTRACT FROM AUTHOR]

Wildfires represent one of the main factors of land degradation in Mediterranean environments having negative effects to several ecosystem services. In this work, the fire-induced changes associated with depth (O horizon and Ah at 0-1, 1-2 and 2-3 cm depths) were studied in a gypseous soil under Aleppo pine forest. Topsoil monoliths were burned in an outdoor combustion tunnel simulating a fire of moderate intensity. In the O horizon, burning caused an immediate and significant decrease in water repellency (WR), total organic carbon (TOC) and pyrolyzed carbon (PyC) and an increase in total inorganic carbon. The Ah horizon was also significantly affected by fire, but mainly in its first shallower centimetre and with a different direction according to soil properties: TOC, gypsum, WR and PyC decreased, whereas soil aggregate stability and pH increased. Soil burning not only involved the loss of the pre-fire organic matter content of the O horizon and the upper centimetre of the Ah horizon but also decreased their relative abundance of markers of resins, lignin and polysaccharides. Moreover, the soil burning exerted the cracking of alkylic long-chain molecular series, some of them until the 2 cm Ah depth. The reduction of organic lipophilic molecules in the upper soil centimetre may be related to the fire-induced decreases in WR. Moderate burning of the studied gypseous ochric horizon does not modify any of the properties studied at depths greater than 2 cm. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Assessing the joint development of vegetation cover and soil properties is crucial to evaluate the efficiency of soil bioengineering techniques, especially during the most critical initial phase of vegetation colonization. We set up a laboratory experiment to quantify and disentangle the effect of Alnus incana roots on soil permeability and aggregate stability. Plants were grown in pots in a climate chamber for four different growing periods (1, 2, 4 and 8 months). Pots were filled with a soil coming from a moraine of a landslide area in Central Switzerland. After each growing period, surface permeability, soil volume permeability and soil aggregate stability were measured together with the development of the root systems. Our results show that alder roots significantly improve both surface and whole soil volume permeability already after 2 months of growth. Nevertheless, an increase in root length density does not necessarily correspond to an increase in permeability. We could set as a threshold a root length density of 0.1 cm/cm3 until which an increase in root development corresponds to an increase in soil permeability, whereas after this threshold we observed a decrease in soil permeability. A significant increase in soil aggregate stability could be observed only with a root length density of 2 cm/cm3. No obvious correlation between soil permeability and aggregate stability could be found. Future work should validate these laboratory results with field data. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Soil aggregate stability is a key indicator of soil resistance to erosion, but its measurement remains fastidious for large scale uses. Alternative time and cost-effective methods are thus needed. Our objective was to assess and compare the efficiency of laser granulometry (LG) and soil mid- and near-infrared spectroscopy (MIR/NIR) as alternative methods to assess soil aggregate stability in Mediterranean badland soils. A collection of 75 badland soil samples was used, showing wide variations in soil aggregate stability. Three different categories of measurements were performed: (i) the aggregate breakdown kinetics of the [< 1 mm] size fraction under stirring and sonication, tracked by repeated particle size distribution measurements, using LG, (ii) mid-(diffuse-MIR-DR and attenuate transmitted reflectance — MIR-ATR) and near-(NIR-DR) infrared spectra of the fine soil fraction [< 2 mm] and (iii) the soil aggregate [3–5 mm] stability, using the standardized method (ISO/FDIS 10930, 2012). Partial least squares regression models were used to predict soil aggregate stability using LG data and infrared spectra. Results showed that NIR-DR and MIR-ATR data provided the best prediction model for soil aggregate stability values (RPD = 2.61 & 2.74; R 2 = 0.85 & 0.87), followed by MIR-DR data (RPD = 2.24; R 2 = 0.89) and finally LG data (RPD = 2.12; R 2 = 0.80). For a quantitative use of the models to assign soil samples to standardized soil aggregate stability classes (ISO/FDIS 10930, 2012), infrared spectra also provided the best accuracy, with a misclassification rate below 30% for NIR-DR and MIR-ATR models, while it reached 43% with the LG-based model. The combination of IR and LG data did not yield a better prediction model for soil aggregate stability values and classes. Infrared-based method also provided best results in terms of time-saving strategy, reducing the measurement time to 8 min only. To conclude, infrared spectra (NIR-DR and MIR-ATR) outperformed LG-data to predict soil aggregate stability. Further development of this technique would require calibrating a set of soil-type specific prediction models for a wide range of soil types. [ABSTRACT FROM AUTHOR]

Biochar (BC) has been reported to improve soil physical properties mainly in laboratory and greenhouse pot experiments. Here we study, under field conditions, the effect of BC and its particle sizes on soil aggregate stability, bulk density (BD), water retention, and pore size distribution in two experiments in Zambia. A) Farmer practice experiment in sandy loam with maize cob BC in conservation farming planting basins under maize and soybeans crops. B) Maize cob and rice husk BC particle size experiments (≤0.5, 0.5–1 and 1–5 mm particle sizes) in loamy sand and sand. In the farmer practice experiment, BC increased aggregate stability by 7–9% and 17–20% per percent BC added under maize and soybeans crops respectively ( p < 0.05) after two growing seasons. Total porosity and available water capacity (AWC) increased by 2 and 3% respectively per percent BC added ( p < 0.05) under both crops, whereas BD decreased by 3–5% per percent BC added ( p ≤ 0.01). In the maize cob BC particle size experiment after one growing season, dose was a more important factor than particle size across the soils tested. Particle size of BC was more important in loamy sand than in sand, with ≤0.5 and 1–5 mm sizes producing the strongest effects on the measured properties. For example, BD decreased while total porosity increased ( p < 0.01) for all BC particle sizes in sand whereas only 1–5 mm BC significantly decreased BD and increased total porosity in loamy sand ( p < 0.05). However, AWC was significantly increased by only ≤0.5 and 1–5 mm BCs by 7–9% per percent BC added in both loamy sand and sand. Rice husk BC effect after one year followed similar pattern as maize cob BC but less effective in affecting soil physical properties. Overall, reduced density of soil due to BC-induced soil aggregation may aid root growth and with more water available, can increase crop growth and yields. [ABSTRACT FROM AUTHOR]

Surface charges can produce strong electric field around soil particles, and profoundly influence soil water movement. The influence of soil electric field on water transport in soil column with a permanently charged soil was studied. It was found that soil electric field influences soil water transport by affecting: (1) the electrostatic forces between the electric field and water molecule dipole; and (2) soil water conductivity through controlling stability of soil aggregates. When soil electric field was high, soil aggregates were broken and soil electric field influenced soil water transport through its effect on the interaction forces between water dipole and the electric field. Conversely, when soil electric field was low, the effect of soil electric field on soil water transport was mainly through its influence on soil aggregate stability. The surface potential of 153 mV for the soil was the critical potential, below this potential, the influence of soil electric field on soil aggregate stability was the main mechanism affecting soil water transport; and above this potential, the effect of soil electric field on the interaction forces between water dipole and the electric field was the main influence on soil water transport. This study suggests that it might be possible to regulate soil water transport by adjusting soil electric field using electrolytes. [ABSTRACT FROM AUTHOR]

Background and aims: Our objectives were to evaluate changes in soil aggregate stability along a successional gradient, located in severely eroded Mediterranean gully bed ecosystems and to identify predictors of soil aggregate stability variations among several soil, root traits and plant community characteristics. Methods: We selected 75 plots in gully beds, representing five successional stages that differ in plant community composition, dominated by herbs, shrubs or trees according to successional stage. In each plot, we measured soil aggregate stability, basic soil characteristics, root traits and plant diversity indices. Results: Soil aggregate stability increased along the successional gradient, being thrice higher in tree-dominated communities as compared to grass-dominated communities. This increase was mainly driven by soil organic carbon (SOC) accumulation. In early successional stages showing low SOC (below 24 g.kg or 12 g.kg in some cases), fine sand content and the percentage of fine roots acted as co-drivers enhancing soil aggregate stability while silt content decreased it. Conclusion: Plant succession in severely eroded Mediterranean gully bed ecosystems is accompanied by a strong stabilization of soil aggregates, mainly driven by SOC accumulation and for early successional stages, by soil granulometry and root traits as co-drivers. Stimulating succession thus appears as a promising restoration strategy for severely eroded ecosystems. [ABSTRACT FROM AUTHOR]

[Display omitted] • Forest conversion (FC) reduced bulk SOC in forest plantations but not ANR forest. • Aggregates stability is higher in ANR forest than plantations following FC. • FC did not change bulk SOC composition in ANR forest. • FC increased aromatic C and reduced O-alkyl C in Castanopsis plantation. • SOC significantly correlated with soil aggregate stability but not C recalcitrance. Preservation of biochemically recalcitrant organic matter and protection within soil aggregates are two important mechanisms of soil organic carbon (SOC) preservation, but their relative importance remains unclear. In this study, we converted part of a mature secondary forest to two young plantation forests (Castanopsis carlesii and Chinese fir) and an assisted naturally regenerated (ANR) forest in 2012. The three young forests (five years old at the time of study) and the remaining mature secondary forest constitute a soil disturbance intensity gradient ideal for exploring effects of forest conversion on soil aggregate size classes and stability as well as SOC concentration and chemical composition. Taking advantage of the disturbance gradient, we examined the relative importance of physical protection versus recalcitrance in SOC preservations. We found that the young ANR forest conserved a similar amount of SOC to that of the mature secondary forest, which was 18 %–21 % higher than those retained in the two young plantations. Compared with the mature secondary forest, the young ANR forest retained 87 % of >2 mm aggregates, whereas the two young forest plantations retained only 45 %–53 %. Compared to the mature secondary forest, aggregate mean weight diameter (MWD) decreased by 10 % in the young ANR forest and 37 %–43 % in the two young plantations. Moreover, the young Castanopsis carlesii plantation had proportionally more recalcitrant aromatic carbon (C) and less labile O -alkyl C compared to the mature secondary forest. Total SOC was positively related to >2 mm aggregates mass percent, soil aggregate MWD, and labile O -alkyl C, but not with recalcitrant alkyl and aromatic C. Our results indicate that SOC preservation is more related to soil aggregate stability than recalcitrant C abundance, and advocate that reducing soil disturbance is key to future forest management aiming to maximize C sequestration. [ABSTRACT FROM AUTHOR]

The aim of global carbon (C) neutrality brings soils and their potential for C storage into the spotlight. Improved agricultural management techniques such as minimum or no-tillage are thought to foster soil C sequestration. However, the underlying mechanisms are still not well understood. In this study, we investigated the inter-relations of soil organic C (SOC), fungal biomass, microbial necromass biomarkers, and aggregate stability in rhizosphere and bulk soil after thirteen years of reduced tillage intensities (reduced, minimum, and no-tillage). Overall, rhizosphere and bulk soil were indifferent in their response to reduced tillage. Reducing tillage intensity increased SOC and nitrogen stocks and dissolved organic C contents in the following order: minimum > no-tillage > reduced > conventional. Aggregate stability showed the strongest increase under no-tillage. Interestingly, ergosterol contents were highest under reduced and minimum tillage followed by no-tillage. The amino sugars muramic acid, galactosamine, and glucosamine – proxies for soil microbial-derived necromass – showed similar increases under all three tillage reduction systems. Structural equation modelling revealed that increased dissolved organic C contents under reduced tillage intensity facilitated SOC sequestration and aggregate stability through enhanced fungal biomass to necromass turnover. Thus, reducing soil tillage intensity is a valuable tool to facilitate microbial growth and hence to increase SOC sequestration in agricultural soils. • Tillage intensity reduction increases fungal abundance and microbial necromass. • Responses of selected soil parameters are more pronounced in minimum and no tillage. • Bulk and rhizosphere soils have minor difference of responses to tillage intensity. • Soil fungi facilitate soil carbon sequestration and aggregate stabilization. • Microbial carbon assimilation is a prominent pathway for soil carbon accumulation. [ABSTRACT FROM AUTHOR]

[Display omitted] • OC and TN in aggregates were negatively correlated with aggregate size and soil depth. • Sheet erosion reduced aggregate stability and thus aggravated losses of OC and TN. • Woodland soil had higher aggregate OC, TN and stability compared to agricultural soil. • Land-use affected aggregate stability by changing bulk soil properties, OC and TN in aggregates. Soil aggregate stability is considered as one of the most sensitive parameters that reflect soil structure and quality, which is significantly influenced by soil organic carbon (OC) and total nitrogen (TN). However, the responses of soil OC and TN contents in both bulk soils and aggregates to aggregate stability as affected by land-uses remain unclear, especially under sheet erosion condition. Thus, aiming to investigate the effects of different land-use types on soil aggregate stability, aggregate-associated OC and TN contents and the relationships between them under sheet erosion condition in south subtropical zone of China, soil samples from four land-use types were collected at soil depths of 0–10, 10–20 and 20–30 cm, respectively. Results showed that soil water-stable aggregate content (WSA), mean weighted diameter (MWD), geometric mean diameter (GMD), aggregate-associated OC and TN were highest in woodland soil and showed significant differences among different land-use types (P < 0.05), which were mainly because of the differences on aggregate size distributions induced by soil erosion. Soil aggregate-associated OC and TN contents decreased with the increases of aggregate sizes. In addition, soil aggregate-associated OC and TN contents were negatively correlated with aggregate sizes, because of the strong bonding ability among OC, TN, clay particles and aggregates. Moreover, the interactions among soil aggregate-associated OC, TN and physicochemical properties contributed to 81.7 % of aggregate stability, which highlighted the vital role of OC and TN on maintaining soil aggregate stability under sheet erosion condition. Therefore, appropriate agricultural and engineering strategies focusing on the enhancement of aggregate-associated OC and TN should be carried out to maintain soil aggregate stability and reduce erodibility under global sheet erosion condition. [ABSTRACT FROM AUTHOR]

To reclaim a limestone quarry, 200 and 400 Mg/ha of municipal sewage sludge were mixed with an infertile calcareous substrate and spread as mine soil in 1992. Soil samples were taken 1 week later and again after 17 yr of mine soil rehabilitation so as to assess changes in the amount and persistence of soil organic carbon (SOC). Sludge application increased SOC as a function of the sludge rate at both sampling times. Seventeen years after the sludge amendments, the nonhydrolysable carbon was increased in the 400 Mg/ha of sludge treatment. The recalcitrance of SOC was less in sludge-amended soils than in the control treatment at the initial sampling, but 17 yr later this trend had reversed, showing qualitative changes in soil organic carbon. The CO2-C production had not differed between treatments, yet the percentage of mineralized SOC was less in the high sludge dose. When the size of active (Cactive) and slow (Cslow) potentially mineralizable C pools was calculated by curve fitting of a double-exponential equation, the proportion of Cactive was observed to be smaller in the 400 Mg/ha sludge treatment. Soil aggregate stability, represented by the mean weight diameter of water-stable soil aggregates, was significantly greater in mine soil treated with the high dose of sludge (18.5%) and SOC tended to be concentrated in macro-aggregates (5-2 mm). Results suggest that SOC content in sludge-amended plots was preserved due by (i) replacement of the labile organic carbon of sludge by more stable compounds and (ii) protection of SOC in aggregates. [ABSTRACT FROM AUTHOR]

Soil aggregate stability is an important parameter that indicates soil resistance to erosion and the potential productivity of sloping farmland. The cultivated-layer (0–20 cm) of typical sloping purple soil (entisol) farmland around the Three Gorges Reservoir was studied. In-situ controls test and shovel test were used to determine the response of water stable aggregates to two factors, degree of erosion and soil amendment (CK, no fertilizer; F, chemical fertilizer; and BF, biochar with chemical fertilizer) and to analyze regulating pathways of the rational cultivation layer for sloping farmland. Water stable aggregate content for each soil particle size fraction in the cultivated-layer was significantly different for all degrees of erosion. The fraction of particle size > 5 mm in subsurface soil (10–20 cm) was greater than in topsoil (0–10 cm). Erosion significantly affected soil aggregate stability (W R 0.25 , >0.25 mm particle size water-stable aggregates content; MWD, mean weight diameter of aggregates; GMD, geometric mean diameter of aggregates) in the cultivated-layer. Both MWD and GMD reached maximums for S-0 (erosion of 0 cm). Comparing all treatments, it is BF that showed greater weight increase for MWD and GMD in topsoil (0–10 cm). Percentage of aggregate disruption consistently increased along downward direction of erosion degrees. Shear strength and penetration resistance, which are soil macrostructure parameters, were used to quantify soil stability in a short time. Treatment BF resulted in the greatest increase in shear strength in topsoil for S-10 (erosion of 10 cm) and significantly decreased penetration resistance. This treatment could significantly improve soil tillage performance and facilitate the formation of a loose upper and compact lower cultivated-layer. Shear strength responded very significantly to the interactive effects of erosion and soil treatment and was more sensitive to soil treatment. These results demonstrated that erosion makes soil less sustainable by disintegrating macroaggregates, and BF is the better soil management practice to effectively improve aggregate stability of erodible cultivated purple soil. • Response of aggregate stability to erosion degrees and soil amendment treatment were compared. • In-situ control tests and shovel tests were used. • Erosion caused significant difference in water-stable aggregate content for each size fraction. • Biochar with chemical fertilizer increased cultivated-layer soil stability. • The presented work can facilitate optimum management of the cultivation layer of purple soil. [ABSTRACT FROM AUTHOR]

The ability of trees to sequester carbon vary from species to species, this study therefore evaluates the influence of seven tree species (Acacia senegal, Azadirachta indica, Eucalyptus camadulensis, Khaya senegalensis, Prosopis africana, Tamarindus indica and Tectona grandis) on soil aggregate fractions and various pools of carbon in soil at three soil depth (0-5, 5-15 and 15-25cm). Results revealed that most soil quality enhancing properties concentrated more at the soil surface (0-5cm) relative to other depths. Soil planted to T. indica stood out in possessing high proportion of large and small macro aggregates, mean weight diameter (MWD) and least proportion of silt plus clay particles. High proportion of fine particulate organic carbon, particulate organic carbon, silt plus clay associated organic carbon and non hydrolysable organic carbons were attributed to soil under T. indica. Tamarindus indica might be a better choice of the seven tree  species in mitigating green house effects by sequestering atmospheric carbon and improving soil aggregate stability.

Highlights: [•] Changes in rhizosphere properties of trifoliate orange by AMF species were studied. [•] AMF soils had higher SOC, BRSP fractions, aggregate stability and percent of WSA. [•] In BRSP fractions, only fraction 1 was positively correlated with WSA stability. [•] Hyphal length and SOC positively correlated with WSA stability and BRSP fractions. [•] Hyphal length effect on WSA stability was stronger than fraction 1 and SOC. [Copyright &y& Elsevier]

The use of treated wastewater (TWW) for agricultural irrigation becomes increasingly important in water stressed regions like the Middle East for substituting fresh water (FW) resources. Due to elevated salt concentrations and organic compounds in TWW this practice has potential adverse effects on soil quality, such as the reduction of hydraulic conductivity (HC) and soil aggregate stability (SAS). To assess the impact of TWW irrigation in comparison to FW irrigation on HC, in-situ infiltration measurements using mini disk infiltrometer were deployed in four different long-term experimental orchard test sites in Israel. Topsoil samples (0-10 cm) were collected for analyzing SAS and determination of selected soil chemical and physical characteristics. The mean HC values decreased at all TWW sites by 42.9% up to 50.8% compared to FW sites. The SAS was 11.3% to 32.4% lower at all TWW sites. Soil electrical conductivity (EC) and exchangeable sodium percentage (ESP) were generally higher at TWW sites. These results indicate the use of TWW for irrigation is a viable, but potentially deleterious option, as it influences soil physical and chemical properties. [ABSTRACT FROM AUTHOR]