Soil Pore System Research Articles

Heave in the Soil due to Driving Pile Foundations

GIS 150 KV Tambak Lorok III Semarang is a coastal area, stabilization is carried out with piles to reduce land subsidence in the area. In the piling process the soil grains are forced vertically and laterally when the pile foundation is driven into the ground, thus increasing the water pressure in the soil pore system. Nearby buildings will be affected and may suffer damage. The pile driving location for the GIS 150 KV Tambak Lorok III Semarang project is adjacent to other structures. So, the amount of land that needs to be cleared around the project must be calculated. This study uses methodology that makes theoretical predictions about the magnitude of heave caused by piles. Subsequently, vertical ground movement measurements made using the Finite Element Method (Plaxis Program) were compared with the theoretical predictions. Pile depth variations of 45 and 50 meters were performed in the plaxis analysis. In conclusion, the results of the two approaches will be contrasted. In the GIS 150 KV Tambak Lorok III Semarang project, soldier piles with a diameter of about 600 mm were driven 45 meters deep into the ground with hydraulic jacks. The theory led to the conclusion that the heave values for the effect of piling at -45 m depth and at -50 m depth were 0.1285 m and 0.1284 m, respectively. Based on Plaxis pile measurements at a depth of 45 meters, the vertical soil movement value was 5.80 cm, while 4.90 cm was recorded for a depth of 50 meters.

Cover crops effects on anisotropy of unsaturated soil hydraulic properties

No tillage (NT) is frequently implemented in simplified agricultural systems, which has negative effects on soil physical quality. Among the suggested practices to preserve the physical fertility of soils under NT are winter cover crops (CC). Soil physical degradation affects the soil pore configuration and therefore it can generate a change in the directionality of the properties that depend on it. The objective of this study was to determine the effect of cover crop incorporation under NT on the soil pore system configuration and on the anisotropy of the unsaturated hydraulic properties in a Typic Argiudoll. The results showed that the inclusion of cover crops modifies the soil pore configuration increasing the structure porosity. The inclusion of CC modifies the anisotropy of unsaturated hydraulic conductivity in the medium saturation region. The pore size distribution behaves as isotropic as expected for a scalar variable.

Soil water status shapes nutrient cycling in agroecosystems from micrometer to landscape scales

AbstractSoil water status, which refers to the wetness or dryness of soils, is crucial for the productivity of agroecosystems, as it determines nutrient cycling and uptake physically via transport, biologically via the moisture‐dependent activity of soil flora, fauna, and plants, and chemically via specific hydrolyses and redox reactions. Here, we focus on the dynamics of nitrogen (N), phosphorus (P), and sulfur (S) and review how soil water is coupled to the cycling of these elements and related stoichiometric controls across different scales within agroecosystems. These scales span processes at the molecular level, where nutrients and water are consumed, to processes in the soil pore system, within a soil profile and across the landscape. We highlight that with increasing mobility of the nutrients in water, water‐based nutrient flux may alleviate or even exacerbate imbalances in nutrient supply within soils, for example, by transport of mobile nutrients towards previously depleted microsites (alleviating imbalances), or by selective loss of mobile nutrients from microsites (increasing imbalances). These imbalances can be modulated by biological activity, especially by fungal hyphae and roots, which contribute to nutrient redistribution within soils, and which are themselves dependent on specific, optimal water availability. At larger scales, such small‐scale effects converge with nutrient inputs from atmospheric (wet deposition) or nonlocal sources and with nutrient losses from the soil system towards aquifers. Hence, water acts as a major control in nutrient cycling across scales in agroecosystems and may either exacerbate or remove spatial disparities in the availability of the individual nutrients (N, P, S) required for biological activity.

A novel physical-empirical model linking shortwave infrared reflectance and soil water retention

Soil hydraulic properties, including soil water retention, control various terrestrial hydrological processes such as infiltration, runoff, and evapotranspiration. Measuring and monitoring these properties at large scales is challenging. Therefore, over the past decade, remote sensing has been investigated as a promising tool for large-scale mapping of soil hydraulic properties. Nonetheless, a solid physical relationship between soil hydraulic and spectral properties is still lacking. To close this knowledge gap, this study introduces a novel physical-empirical model that to our best knowledge for the first time connects the soil water retention curve (SWRC) to soil spectral reflectance. The new model has been developed based on the hypothesis that the capillary and adsorbed water components of the SWRC exhibit vastly different optical properties due to their distinct distribution within the soil porous system. The model was validated using soil water retention and reflectance measurements of 21 soils, vastly differing in physical and hydraulic properties. The model provides not only a new and accurate soil moisture-reflectance functional relationship, but also a potential means for retrieval of the soil water retention curve from spectral reflectance in the shortwave infrared domain.

An analysis of three XCT-based methods to determine the intrinsic permeability of soil aggregates

• Consistent permeability found in orthogonal flow directions by fluid flow simulation. • Skeletonization was a reliable and quick approach to parametrize Kozeny-Carman. • Pore network modelling was more sensitive to thin ramifications of the pore system. • Faster calibrated XCT-based methods can be used in large datasets for permeability. Nowadays there are many papers dealing with the analysis of the soil porous system through X-ray computed tomography (XCT). However, a reduced number of studies focus on modeling the intrinsic permeability (k) of complex porous media, such as soil, based on three-dimensional (3D) high-resolution images. The determination of k is fundamental to understanding several processes taking place in soil such as water and air transmission. Thus, this paper compares three XCT-based methods for estimating the k of the pore system of soil aggregates: i) Finite volume-based simulation (APES - Absolute Permeability Experiment Simulation), ii) Image-based parametrization of the Kozeny-Carman (IBP-KC) equation, and iii) Pore network model (PNM). The 3D image considered in the comparison of methods was acquired at the X-ray microtomography beamline at the Brazilian Synchrotron Light Facility, with a voxel size of 1.64 μm. APES was considered as a reference method for being less dependent on the configuration of sensitivity parameters. APES and PNM demonstrated to be more time consuming than the IBP-KC, the first taking longer among all for the k computation. PNM presented the drawback of higher sensitivity to thin pore ramifications, resulting in unrealistic values of k and requiring disconnecting one thinner pore to yield permeabilities comparable to the ones obtained by APES. This study demonstrated that a fine alternative to compute k for large image datasets is to calibrate faster methods (e.g., IBP-KC and PNM) against a slower but more reliable reference method (e.g., APES), using at least one 3D image, before applying the faster methods on the remaining images of the dataset.

Soil pore system complexity and heterogeneity as affected by contrasting management practices

To better understand the changes that occur in soil systems at different scales, researchers have been using concepts from the multifractal theory for investigating intricate and heterogeneous complex structures. This analysis has also been applied to understand how complex systems such as the soil behave under contrasting management practices. This study presents the use of the three-dimensional multifractal theory, lacunarity, and normalized Shannon entropy to characterize changes in the porous system of a Rhodic Hapludox under different management practices (conventional tillage, minimum tillage, and no-tillage) compared with the same soil under a secondary forest, assumed as a reference. The results of lacunarity and multifractal spectra revealed separations between management groups in relation to their porous systems (secondary forest with no-tillage and conventional tillage with minimum tillage). These results indicate possible “degradation” in the structure of the soil under conventional and minimum tillage and its preservation when under no-tillage as the complexity of their pores is analyzed. The contrasting management practices and forest presented linear correlations between soil porosity and lacunarities, maximum normalized Shannon entropy, and the multifractal spectra. The degree of multifractal spectra asymmetries and lacunarities evidenced the variability of spatial distributions of the managements and forest pore size diameters, showing that these tools are useful for characterizing the soil pore system. The results obtained showed the potential and sensitivity of the 3D multifractal approach in the characterization and differentiation of complexity in soil management practices.

Impact of using magnetic water on the micro structure of leached saline-sodic soil.

Structural changes in the porous media are critical in evaluating the soil pore system and other physical properties of leached soil. In this work, the combination of selected physical parameters such as bulk density and hydraulic conductivity with images of scanning electron microscopic (SEM) was used to study the impact of five levels (1, 3, 5, 7, and 9 magnets) of magnetically treated water (MTW) on the structural changes in pore spaces of leached high saline-sodic soil, compared with leached soil with non- magnetically treated water (NMTW) and unleached soil. Results show that leaching saline-sodic soil with MTW leads to a remarkable increase in soil pore network as confirmed by SEM observations and ImageJ software program. The influence of MTW is important in all cases but the changes in pores of leached soil were mainly observed when the magnetic fields of 7 and 9 were used. It has been found that the value of total percentage area of pores in the leached soil was found to be 7.55 and 9.53, respectively, while the total percentage area of pores in both leached soil with NMTW and unleached soil were 0.69 and 0.1 respectively. It can be concluded that MTW can improve the physiochemical properties of soils in two ways: first, it accelerates the solubility of salts and increases calcium ion available on the soil exchange surface which displaced a higher concentration of adsorbed sodium ions. Second, the changes in the microstructure lead to improved soil porosity combined with saturated hydraulic conductivity and bulk density. This study will provide a method for using magnetic water technology to improve soil properties greatly by increasing soil porosity. Through this porosity, water, solutes, and gases can diffuse through the ground, thus increasing exchange processes.

Reclamation of Salt-Affected Land: A Review

Reclamation of salt-affected soil has been identified by the FAO as being critical to meet the needs to increase agricultural productivity. This paper reviews commonly used reclamation methods for salt-affected soils, and provides critical identifiers for an effective reclamation practice of salt-affected soil. There are widely used methods to reduce salinity and sodicity of salt-affected soils, including salt leaching, addition of amendments, revegetation using halophytes and salt scrapping. Not all reclamation techniques are suitable for salt-affected land. The reclamation strategy must be tailored to the site, and based on understanding the soil, plant and climate interactions. On some occasions, a combination of techniques may be required for reclamation. This can include salt scrapping to remove salts from the surface soil, the addition of physical amendments to improve soil pore systems and enhance salt leaching, followed by amelioration of soil by chemical amendments to preserve soil physical conditions, and then halophyte establishment to expand the desalinization zone. This study reveals that soil hydro-geochemical models are effective predictive tools to ascertain the best reclamation practice tailored to salt-affected land. However, models need to be calibrated and validated to the conditions of the land before being applied as a tool to combat soil salinity.

Millimetre scale aeration of the rhizosphere and drilosphere

AbstractSoil aeration is a critical factor for oxygen‐limited subsoil processes, as transport by diffusion and advection is restricted by the long distance to the free atmosphere. Oxygen transport into the soil matrix is highly dependent on its connectivity to larger pore channels like earthworm and root colonised biopores. Here we hypothesize that the soil matrix around biopores represents different connectivity depending on biopore genesis and actual coloniser. We analysed the soil pore system of undisturbed soil core samples around biopores generated or colonised by roots and earthworms and compared them with the pore system of soil, not in the immediacy of a biopore. Oxygen partial pressure profiles and gas relative diffusion was measured in the rhizosphere and drilosphere from the biopore wall into the bulk soil with microelectrodes. The measurements were linked with structural features such as porosity and connectivity obtained from X‐ray tomography and image analysis. Aeration was enhanced in the soil matrix surrounding biopores in comparison to the bulk soil, shown by higher oxygen concentrations and higher relative diffusion coefficients. Biopores colonised by roots presented more connected lateral pores than earthworm colonised ones, which resulted in enhanced aeration of the rhizosphere compared to the drilosphere. This has influenced biotic processes (microbial turnover/mineralization or root respiration) at biopore interfaces and highlights the importance of microstructural features for soil processes and their dependency on the biopore's coloniser.

Cation exchange capacity and soil pore system play key roles in water vapour sorption

Understanding the controlling factors of soil water vapour sorption at different water activities (aw) is essential for accurate estimation of soil properties, such as cation exchange capacity (CEC) and specific surface area (SSA). The objective of this study was to identify the role of CEC and soil pore system in water vapour sorption and sorption hysteresis over a range of aw values. The CEC, SSA, pore volume, and water and nitrogen adsorption/desorption isotherms for eight soils with different clay contents and mineralogies were measured. Irrespective of aw and sorption direction, there was a significant correlation between water content and CEC, and the correlation varied with aw. The water content change was mainly related to CEC and SSAH2O for aw < ∼0.6, and to SSAN2 and pore volume for aw > ∼0.6. Similar to the forced closure phenomenon of the soil nitrogen desorption branch at a relative pressure (P/P0) of ∼ 0.45, the soil water vapour desorption branch also exhibited a sudden drop in the range of 0.2 < aw < 0.4. The water vapour sorption hysteresis for aw < ∼0.75 was mainly due to the difference in cation hydration during the adsorption and desorption process, and the hysteresis phenomena for aw > ∼0.75 was attributed to the different sizes of narrow pore necks and the connected pores.

Physical-hydric properties of Oxisols as influenced by soil structure and clay mineralogy

The soil water retention curve (SWRC) and soil hydraulic conductivity (K) are important soil hydraulic properties. In Oxisols, the degree of microaggregation depends on the amount of iron and aluminum oxides, kaolinite and biological activity engaged in modifying the pore size distribution (PSD) of the soil porous system. The objectives of this study were (i) to characterize four Brazilian Oxisols in terms of SWRC and PSD, using undisturbed (structural SWRCs) and disturbed (textural SWRCs) soil samples; (ii) to apply the van Genuchten-Mualem (vGM) model to the prediction of K and (iii) to correlate the classes of porosity and saturated hydraulic conductivity (Ksat) with the physical, chemical and mineralogical properties. Four soils were studied: Xantic Kandiustox, Rhodic Haplustox, Anionic Acrustox and Typic Hapludox. The soil samples were collected from the Bw horizon of each soil. The structural SWRCs were determined by Haine’s funnels and Richards’ chambers, whereas the textural SWRCs were determined by dew point meter. Ksat was evaluated by constant head permeameter and, additionally, soil chemical and mineralogical analyses were prepared. It was concluded that: (i) the four soils showed bimodal PSD; (ii) the four soils presented the maximum frequency of equivalent radius in the class of macropores (structural SWRCs) with rmax varying between 43.37 and 88,98 μm, and in the class of cryptopores (textural SWRCs) with rmax varying between 0.012 and 0.014 µm; (iii) the higher the Ksat, the higher the K predicted by the vGM model over the entire soil water content range of the structural SWRCs, except for Xanthic Kandiustox and Typic Hapludox in which this phenomenon occurred closer to saturation; (iv) the K values estimated by the vGM model from textural SWRCs were very low, varying approximately from 10−25 to 10−11mm h−1 for the four soils; (v) the degree of microaggregation of Rhodic Haplustox and Anionic Acrustox resulting from the high levels of Fe and Al oxides, leading to the formation of greater inter-aggregate space, had an influence on the high Ksat and showed that the mineralogy of the clay fraction was decisive in the physical-hydric behavior of these soils.

Cation Exchange Capacity and Soil Pore System Play the Key Role in Water Vapour Sorption

Cation Exchange Capacity and Soil Pore System Play the Key Role in Water Vapour Sorption

Characterisation of soil pore structure anisotropy caused by the growth of bio-subsoilers

Deep-rooting cover crops (tap-rooted plants and grasses) are suggested to enhance soil properties when used as bio-subsoilers in compacted soils. However, there is limited knowledge the impact of bio-subsoilers on anisotropy of the soil pore system of compacted zones. The objective of this study is to evaluate the impact of different bio-subsoiler species on the anisotropy of the soil pore characteristics of a compacted sandy loam subsoil. The experimental treatments consisted of spring barley as control and chicory, lucerne and tall fescue as bio-subsoilers. The soil samples were taken in both vertical and horizontal directions at 0.3–0.4 m depth. Air permeability (ka) and air-filled porosity (εa) were quantified at −10, −30, −50, −100 and −300 hPa matric potential, and X-ray computed tomography (CT) scans were obtained for samples drained at −100 hPa. Results showed no significant treatment effect (p < 0.05) on ka, the ratio of the non-Darcian to the Darcian air permeability (R), or the PO1 index (ka/εa) in either vertical or horizontal directions. However, the factor of anisotropy of ka, PO1 and R-ratio was significantly affected by chicory and lucerne (p < 0.05), indicating the creation of more vertically than horizontally oriented pores. The results from measured parameters were supported by CT image analysis as macropores connecting from end-to-end of the soil cores were mainly captured for vertically oriented samples by the CT scanner. Lucerne had significantly larger proportion of CT-macroporosity (∼50%) and CT-total branch length (∼40%) for vertically connected pore network as compared to spring barley (∼20% for both parameters). This study suggests that the impact of growing bio-subsoilers on the anisotropy of the soil pore system of the studied compacted subsoil is species-dependent.

Plant species and plant neighbor identity affect associations between plant assimilated C inputs and soil pores

Greater plant diversity is known to facilitate soil C gains, yet the exact mechanisms of this effect are still under intensive discussion. Whether a plant grows in monoculture or in a multi-species mixture can affect allocation of plant assimilates, belowground exudation, and microbial stimulation. The goal of this study was to examine the effects of inter-cropping on a previously overlooked aspect of plant-soil interactions, namely, on locations where plant assimilated C is allocated within the soil pore system and its subsequent fate in relation to soil pore size distributions. The soil for the study originated from a greenhouse experiment with switchgrass (Panicum virgatum L.) (var. Cave'n'Rock) (SW), big bluestem (Andropogon gerardii Vitman) (BB), and wild bergamot (Monarda fistulosa L.) (WB) grown in monocultures and in inter-cropped pairs and subjected to species specific 13C pulse labeling (Kravchenko et al., 2021). Intact soil cores (8 mm Ø) were collected from the experimental pots, subjected to a short-term (10 day) incubation, X-ray computed micro-tomography (µCT) scanning, and soil 13C micro-sampling “geo-referenced” to µCT images. Results indicated that in the plant systems with demonstrated interplant C transfer soil 13C was positively correlated with < 10 µm Ø pores immediately after plant termination and with 20–80 µm Ø pores after the incubation. In the systems without marked interplant C transfer soil, 13C was positively correlated with 20–30 µm Ø pores, however, the correlations disappeared after the incubation. Soils from the systems with demonstrated belowground C transfer displayed lower losses of root-derived C during incubation than the systems where interplant C transfer was negligible. Factors facilitating interplant C transfer appear to also lead to placement of root-derived C into smaller pores and to its greater protection there.

Suitability of Image Analysis in Evaluating Air and Water Permeability of Soil

A comprehensive understanding of the water and air permeability of soil is necessary for modelling the transport properties which depend on soil structure. We aimed to evaluate the suitability of image analysis to estimate gas and liquid transport in soil using resin-impregnated soil blocks. The soil texture, TOC, density, porosity, air capacity (VV), air permeability (logAP), and the saturated hydraulic conductivity (logKS) of a Cambisol developed from loess were measured. To characterise the pores, using the soil structure images, we determined the macroporosity (AA), index of soil pore-network growth rate, percolation number (lognPER), length of pore path/unit area (PLA), and relative volume of pores overlapping top and/or bottom edge of the image (VTB). logKS and logAP related to morphometric parameters of soil structure derived from the image analysis. The main factor controlling the soil’s infiltration was the total volume of soil pores (VV and AA). AA, PLA, VTB, and lognPER were equally useful for characterising the soil pore system. These results will contribute to more accurate estimations of gas and liquid transport in soils and allow to obtain historical hydraulic properties and model long-term trends in the soil water regime based on the existing collections of thin sections and polished blocks.

Conservation tillage rotation enhanced soil structure and soil nutrients in long-term dryland agriculture

Conservation tillage has been proposed as an effective way to conserve soil water in dryland agriculture. However, long-term continuous mono-tillage including conservational and conventional tillage has been proved to have limited improvements or some defects on soil structure and nutrients enhancement. Combining different tillage practices in a rational rotation that adapts to the cropping system may optimize the advantages and improve the potentials of mono-tillage practices. Soil porosity, aggregates, water, organic carbon, nitrogen and crop yield were investigated in a ten-year (2007–2016) long-term conventional with conservation tillage rotation experiment which contained four tillage systems, NT (no-tillage), ST (subsoiling), CT (conventional tillage), and NCS rotation (no-tillage, conventional tillage and subsoiling rotated annually) in a dryland field to assess the soil pore system, aggregates, nutrients content and productivity. Compared with three mono-tillage systems (NT, ST and CT), the NCS rotation significantly decreased soil bulk density by 3.8–8.4 % and increased soil porosity by 3.2–6.7 % (P < 0.05) after ten years. NCS rotation increased soil capillary porosity by 9.7–36.3 %, reduced inactive porosity by 4–8.1 % when compared to continuous mono-tillage (NT, ST and CT), optimized soil porosity distribution at 0−60 cm soil depth till the tenth year. Meanwhile, compared with mono-tillage, NCS rotation improved soil macroaggregates content (0.25–5 mm) by 35.2–46.4 % and resulted in 40.3–113 % higher macroaggregates content than ten years before at 0−40 cm soil depth (P < 0.05). As the experiment continues, soil organic carbon (SOC) and nitrogen (TN) at different tillage systems accumulated at rates of 1.65−2.01 Mg ha−1 year−1 and 0.14−0.21 Mg ha−1 year−1, respectively, NCS rotation resulted in the highest soil nutrients accumulation (SOC: 57.98 Mg ha−1, TN: 6.40 Mg ha−1), better soil nutrients distribution and suitable C/N (9.01) for crop growth and soil enhancement. Additionally, NCS rotation conserved more soil water in fallow period (394 mm) and during crop growth season (winter wheat: 352 mm, spring maize: 384 mm), produced higher winter wheat (5169 kg ha−1) and spring maize yield (8251 kg ha−1). The long-term rotational research showed that NCS rotation optimized soil structure (soil porosity, soil aggregates) and enhanced soil nutrients (SOC, TN), provided better soil conditions for crop production in dryland rain-fed farming agriculture.

Soil burrow characterization by 3D image analysis: Prediction of macroinvertebrate groups from biopore size distribution parameters

Although scientific literature focuses mainly on earthworms, all soil macroinvertebrates play an important role in modifying the architecture of the soil pore space and, in turn, in soil functions. Notwithstanding the fact that non-invasive technology, such as X-ray tomography, has long been used to differentiate non-biopores from biopores, it is still difficult to distinguish the specific contribution different macroinvertebrates make to the soil biopore system. Unlike the object-based image analysis approach, when applied to a soil pore system, mathematical morphology permits the user to obtain a very accurate pore size distribution consistent with the physical principle of water retention. The aim of this work was to evaluate the potential of the parameters of this kind of biopore size distribution to differentiate between the burrows of five different macroinvertebrate groups, namely Earthworms, Millipedes juliform, Centipedes, Campodeiform larvae and Elateriform larvae, inoculated into repacked soil mesocosms and incubated (14 days) in the field from where the soil animals were originally collected.A two-fold approach was proposed in this work so as to obtain parameters by both pore size population distributions and Weibull modelling of the cumulative distributions. Then a predictive discriminant analysis was performed on selected parameters by using macroinvertebrate groups as grouping variables and a very good prediction was obtained in both cases. The most useful parameters were the skewness and FFT indices in the first case and the shape parameter α of the Weibull model along with its RMSE in the second one. In addition, topological characterization was performed on gallery-shaped biopores. Vertical deviation was the only parameter that was independent of the individual body size and showed the statistically significant lowest value for the earthworms. The experiment and analyses performed in this work to explore the connection between macroinvertebrate groups and the corresponding biopore size distributions may represent a suitable methodological approach to performing a general investigation into the relationships between soil management and its impact on the system of soil macropores.

A meta-analysis of the impact of traffic-induced compaction on soil physical properties and grain yield

Soil compaction caused by wheel traffic is a major driver of soil degradation in modern agriculture and thus, a threat to agricultural sustainability. To improve the predictive capacity of compaction models and to support decision-making that implements site-specific practices for ameliorating soil compaction effects in modern agriculture, we need quantitative syntheses of the effect of soil compaction on soil physical properties and crop types. In this work, we used a meta-analytical approach to summarize results from 51 published articles on the impacts of soil compaction attributed to machinery axle load, wheel passes, compaction events and tire inflation pressure on soil bulk density (ρb), degree of compactness (DC), penetration resistance (PR), volume of water filled pores at field capacity (θFc), air permeability (ka) at field capacity, saturated hydraulic conductivity (ksat), and grain yield of corn (Zea mays L.), wheat (Triticum aestivum L.), barley (Hordeum vulgare L.) and soybean (Glycine max L.). Results from this meta-analysis (MA) showed that compaction increased soil mechanical strength shown by increased soil ρb, DC and PR. However, an increase in soil strength was more pronounced in the medium- and coarse-textured soils, and mainly in the topsoil (0–30 cm depth). Penetration resistance for the non-compacted soil (control) treatment was 1.21 MPa for the coarse-textured, 1.11 MPa for the medium-textured and 0.93 MPa for the fine-textured soils. Soil compaction on average, increased PR by 99, 94 and by 41 percent in the medium-, coarse- and fine-textured soils. Compaction decreased hydraulic conductivity characterized by ka and ksat from the topsoil down to the subsoil (>40 cm depth), and grain yield of corn, wheat, barley, and soybean. Overall, compaction decreased grain yield on average by 6–34 percent. Findings of the MA suggest that soil hydraulic properties may be more sensitive indicators to reflect the impact of soil compaction on soil structure and pore system functions in the soil profile. Future efforts should place a greater emphasis on the publication of complete metadata that allows replication and accurate comparison of results across studies and on providing open access to original datasets that can be used to improve our understanding of the effect of traffic-induced compaction on soil functioning, including crop production.

Land-use change affects soil hydro-physical properties in Mollisols of semiarid Central Argentina

The objective of the present study was to describe the relationships between soil physical properties and to identify variables that determine the pore system and hydrological functions which are specifically important in drought prone semiarid marginal croplands. We compared Mollisols under natural vegetation (NV) with their agriculture (AG) pairs in the central Argentinean Dry Pampas to obtain the range of values for variables that characterize the soil pore system. These were total carbon (OC), bulk density (BD), structural instability index (SII), volumetric weight of aggregates (VAW), total porosity (TP), macropores (Ma), saturated hydraulic conductivity (K), infiltration rate (IR), Dexter's S index (S), and least limiting water range (LLWR). To a depth of more than 23 cm, TP and Ma were considerably lower (~ 35% and 50% less, respectively) in AG versus NV. The changes in porosity and pore size resulted in 74% smaller IR and 65% lower K. The S index had mean values of 0.16 and 0.14 for the upper and middle layer respectively in NV; while for AG, these values were significantly lower (0.09 and 0.10, respectively). The LLWR was also lower in AG (21 and 59% less in the upper and middle layer, respectively), due to high soil resistance even at non-limiting BDs (1.17 and 1.32 g cm−3 for AG2 and AG1, respectively). Soil OC was positively correlated with TP, Ma, and S, and negatively correlated with BD and SII. Multiple regression models for S included SII, TP, and clay contents, while for LLWR the variables were OC, TP, and clay plus silt. Thus, these complex soil quality indices can be predicted by using simpler physical parameters, but texture and organic matter also have a strong effect on them. Moreover, our results contribute to a better understanding of the role of texture and organic matter in controlling soil physical quality and for maintaining soil-based ecosystem services.

Quantification of soil structure via synchrotron X‐ray tomography after 22 years of fertilization

AbstractApplying fertilizers on a long‐term basis can promote the accumulation of soil organic matter and increase soil aggregation. The effects of organic and inorganic fertilizers on soil structure have manifested as different morphological characteristics for different soil types. To quantify the three‐dimensional (3D) pore structure of soil cores after long‐term fertilization, we collected cinnamon soil (Chromic Luvisol) aggregates and 2 cm × 2 cm × 2 cm soil cores from a long‐term fertilization field trial beginning in 1989. The treatment groups included no fertilization (CK), inorganic fertilization (NPK) and organic fertilization (OF). Synchrotron radiation‐based X‐ray microcomputer tomography (SR‐μCT) and digital image analysis were used to determine the soil core structure. The results showed that the long‐term practices of OF treatment increased the stability of wet aggregates. Combined visualization of the soil structure and morphological parameters consistently revealed that the soil pore systems under OF treatment were more connected and multilevel than those under the CK treatment after 22 years. The soil pore structures under the CK and NPK treatments were similar but significantly different from the structure under the OF treatment.Highlights Effect of long‐term organic and inorganic fertilization on soil structure was explored. SR‐μCT and digital image analysis techniques were applied to visualise the soil 3D pore structure. Long‐term application of organic fertilizers promoted the number of pores in soil aggregates. OF‐treated soil had more macropores and better continuity between the pores with longer path lengths.