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Freezing and thawing affect the pore-space structure in agricultural soils with implications for soil hydraulic properties and water flow. Previous studies have focused on the upper few centimeters of the tilled topsoil, where most freeze-thaw (FT) cycles occur, even though deeper soil layers are also subject to freezing and thawing in cold climates. Thus, little is known about how freezing and thawing affect untilled soil layers, which often show high bulk densities that restrict vertical water movement. Furthermore, it remains unclear how shifts in FT patterns with climate change may change the pore-space structure and water flow through these soil layers. Here we investigated the effects of freezing and thawing on X-ray imaged pore-space characteristics, water retention and near-saturated hydraulic conductivity (K) in untilled soil directly below plough depth. Intact cores were sampled at two sites in central Sweden under the same long-term reduced tillage management. The two soils, a silt loam and a silty clay loam, were subjected to three FT scenarios in a laboratory environment intended to represent FT patterns that are considered likely under current and future winter conditions for this region. The latter scenario was characterised by more FT cycles and a lower freezing temperature. Freezing and thawing increased K in the near-saturated range in both soils, which we attribute to observed small (<0.01 mm3 mm−3) increases in the volume of pores of diameters close to the X-ray resolution limit. Concomitant increases in pore network connectivity and critical pore diameter, especially in the denser silty clay loam soil, probably contributed to this increase in K. The water retention data suggested that changes in pore-space characteristics below X-ray resolution also occurred in both soils. Furthermore, our results indicate that both soils may show higher drainage rates due to shifts in FT patterns in the future, although longer-term changes in pore-space structure with an increasing number of FT cycles would mostly be limited to soils with relatively high clay contents. These soils are often more compacted below plough depth and, thus, benefits from improvements in soil structure such as improved root growth and plant water supply are also expected to be larger. • Freezing and thawing affects the soil pore structure of compacted soil layers. • Changes in freeze-thaw patterns may increase drainage rates of compacted soils. • Potential benefits are expected to be largest for clay-rich soils.. [ABSTRACT FROM AUTHOR]

The increase in heavy machinery traffic due to crop sequence intensification under no-tillage (NT) management can lead to soil compaction, modifying the soil pore configuration, with negative effects on water dynamics. The objective of this work is to evaluate the residual effects of repeated machinery traffic under different soil water contents on the anisotropy of soil hydraulic properties. The residual effect of repeated machinery traffic under different soil moisture conditions (partially dry, PD, and wet, W) on soil compaction was evaluated and compared with the control treatment (no traffic, T0). Field infiltration using tension disc infiltrometer was carried out, and in laboratory, in order to analyse the anisotropy of soil hydraulic properties infiltration experiments were carried out on vertical and horizontal undisturbed soil samples. No significant differences in field soil hydraulic conductivity K(h) were observed between treatments. The W treatment showed a decrease on the transmission and storage pores in the vertical direction, as compared to T0. Anisotropic behavior of soil hydraulic properties was observed for the compacted treatments. The W treatment showed an increment in the transmission porosity in the horizontal direction. In addition, the W treatment presented higher values of transmission and storage pores in the horizontal direction as compared with the vertical direction. From laboratory infiltration experiments, it was observed a strong reduction on the hydraulic conductivity measured at 0, − 3 and − 6 cm water pressure heads (K 0 , K 3 and K 6) in the vertical direction under W treatment. An anisotropic behavior for both compacted treatments was observed, with higher values of K 0 in the vertical direction under the PD treatment and higher values of K 0 and K 3 in the horizontal direction under the W treatment. These results show that machinery traffic under wet conditions causes a disruption in soil porosity, not only with a reduction of the pore space, but also with a change in its configuration. ● Machinery traffic effects on soil hydraulic properties were studied. ● Anisotropy of soil hydraulic properties was determined using mini-infiltration. ● Traffic in wet conditions causes higher K (h) in the horizontal direction. ● Soil compaction under wet conditions changes the pore system connectivity. [ABSTRACT FROM AUTHOR]

Water flow in the unsaturated zone is an important component of the water cycle. Linearized methods have been widely adopted to solve unsaturated flow problems described with Richards' equation, which is nonlinear. To better understand the effect of unsaturated soil water transport function linearization, this article presents an analytical study of a two-dimensional soil water flow system. Analytical solutions, experimental observations and numerical simulations were compared, and the results indicated that the soil water content variation trends were the same, but the values were a little different. The analytical solutions have a certain reference value for researching unsaturated water flow. However, the soil volumetric water content (SWC) results were sensitive to linearized water flow parameter variations in soil water diffusivity (D). The D changes with the SWC. The results showed that unsaturated water flow function linearization affected the analytical solution results essentially. As the nonlinear math problem was not solved, we recommend the numerical solution when more precise values are needed and complex conditions are considered. • Proposing an analytical solution of two-dimensional soil water transport under mulched drip irrigation. • Discussing the linearization methods of the unsaturated hydraulic conductivity for the analytical solution. • Verifying the applicability of the proposed analytical solutions. • Discussing the effect of unsaturated soil water transport function linearization. [ABSTRACT FROM AUTHOR]

Water repellency related to organic matter (OM) of coatings along the earthworm burrows (EB) walls can facilitate preferential flow due to limiting the water exchange with the soil matrix. The objectives of this work were (i) to characterize the hydraulic behavior of EB wall and the surrounding matrix using a miniaturized infiltrometer; (ii) to compare standard infiltration analyses with BEST-W R algorithm; and (iii) to determine the local spatial distribution of water repellency at the EB wall surface in relation to that of the OM composition. Infiltration experiments were carried out on intact sample surfaces, including the EB wall and the surrounding matrix. Soil samples were collected from Bt and C horizons in a characteristic Haplic Luvisol. Hydraulic conductivity (K) at different water pressure heads (h) and water and ethanol sorptivity (Sw and Se, respectively), water repellency index (RI) and water repellency cessation time (WRCT) were determined from infiltration data. The adapted Beerkan Estimation of Soil Transfer parameters (BEST) algorithm for water-repellent soils (BEST-W R) was used for analysing infiltration data. The potential water repellency index (PWRI), relating C-H with C O functional groups in OM, was determined at the same locations using diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. Lower values of K and Sw in the coatings as compared to the soil matrix were found related to higher PWI values. Water repellency was also reflected in the shape of the cumulative infiltration curves and in the RI-values. The latter were significantly higher for EB as compared to matrix surfaces. The fittings provided by the BEST-W R algorithm characterizing the hydraulic properties of the macropore surfaces were comparable to those obtained with standard method. The tested methods could help to improve the estimation of parameters for macropore-matrix mass exchange in two-domain models. • Mini-infiltration was used for hydraulic characterization of earthworm macropore. • Organic matter (OM) composition was determined with DRIFT spectroscopy. • OM's hydrophobic functional groups reduce hydraulic conductivity and sorptivity. • BEST-W R could be used for macropore-matrix mass exchange parameters estimation. [ABSTRACT FROM AUTHOR]

Studies that elucidate the likely differential impact of biochar produced from different parts of the same plant on soil functions and structure are scanty. Therefore, in this study, biochar made from 2 feedstocks: Mango Twig (B 1) and Mango Branch (B 2) were pyrolyzed at 550 ○C, and mixed with 2 differently textured substrates (silt loam – S and sandy loam –SD) at application rates of 0%, 3%, 4.5% and 6%, and uniformly prepared to a bulk density (BD) of 1.4 g cm−3. The substrates were subsequently subjected to standard procedures to characterize the affected water retention properties, air permeability, and saturated hydraulic conductivity (K s). The results indicate marked differences in the impact of biochar types on the available water and water retention capacity, depending on soil texture. The significant main effect of the biochar type on K s in silty loam and the plant available water capacity in sandy loam highlights the relevance of the selected part of the feedstock pyrolyzed. The optimum amount of biochar required to achieve a significant increase in soil water content was about 3% in both substrates, while air permeability and pore continuity were significantly altered at about 6% biochar amendment rate. Moreover, significant (P < 0.05) improvements in the saturated hydraulic conductivity were observed in the biochar-amended soil compared to the control. Air permeability decreased as the added biochar increased, while the air-filled pores increased at defined matric potential in all treatments. The improvement in soil functions was mostly due to the modification of soil structure parameters (pore size distribution (PSD) and pore continuity), due to increased meso pores concomitant with biochar additions; and greater changes were obtained with B 1. The varied impact of the biochar types especially on the soil water retention, available water capacity, pore continuity, and hydraulic properties for the different soil textures showed that even the selected plant part affects the options to improve soil functions. • Biochar produced from different part of mango plant was applied to soils of different textures. • Biochar types and application rates significantly impacted the soil structure differently. • Biochar types influenced soil intensity and capacity functions differently, depending on soil texture. • Improvement in soil functions was mostly due to the modification of soil structure. [ABSTRACT FROM AUTHOR]

Optimizing tillage management is one way to reduce the risk of soil compaction due to traffic load in Northeast China. In this study, we aimed to examine the responses of precompression stress (σ pc), compression index (C c), pore morphology (>30 µm), air-filled porosity (ε a60), air permeability at matric potential of − 60 hPa (k a60) and saturated hydraulic conductivity (K s) to harvest traffic on soil from two contrasting tillage practices using a 10-yr old field experiment. After the crop was harvested with a combine harvester, undistributed soil cores were collected in the 0–10 and 10–20 cm layers from non-traffic and traffic zones of no-tillage (NT) and moldboard plough (MP) plots. In the non-traffic zone, the MP management showed greater total porosity (ε total), ε a60 and macroporosity (ε X-ray) than the NT. There were no differences in pore connectivity, mean pore size and k a60 of the 0–10 cm layer and in K s of the 0–20 cm layer between the two tillage practices, however, more biopores were observed under NT. Harvest traffic showed no significant effects on NT soil. In the MP plots, the ε total , ε X-ray , and pore connectivity, were decreased and pores larger than 0.15 mm were preferentially compacted. As a result of traffic, MP soil displayed lower k a60 in the 0–20 cm layer and lower ε X-ray and connectivity in the 10–20 cm layer. In the NT management, the pore system had greater water and air conduction efficiencies and stable properties. Thus, compared to MP, NT can mitigate the negative effects of harvest compaction on soil in Northeast China. • Compared with MP, NT yields lower porosity and permeability before traffic pass. • After traffic pass, NT shows more stable soil pore system and better permeability. • NT mitigates the negative effects of harvest traffic on soil pores and permeability. [ABSTRACT FROM AUTHOR]

Crop management practices such as rotation, as well as climatic and edaphic factors, modulate soil physical health. However, the overall magnitude of crop rotation benefits on soil physical health properties across a broad range of different conditions remains uncertain. To address this, we conducted a meta-analysis on 865 paired comparisons from 148 rotation studies to examine i) how crop diversity affected soil physical health properties: bulk density, aggregate stability, porosity, infiltration rate, and saturated hydraulic conductivity, and ii) how management practices, climatic, and edaphic factors influenced crop diversity effects. Overall, increased crop diversity (i.e., number of crop species in the rotation) significantly reduced bulk density (−1.6 ± 1.3%), enhanced soil aggregation (15.9 ± 12.7%), improved porosity (3.1 ± 2.0%), and saturated hydraulic conductivity (112.8 ± 57.9%), but did not significantly change infiltration rate (92.2 ± 98.7%) compared to less diverse systems. Compared to using conventional tillage and cereals-only rotations, diverse rotations combined with conservation tillage or including grain legumes performed even better in enhancing both soil aggregation and porosity. Diverse crop rotations managed for 5–10 yr showed greater benefits in regions experiencing mean annual precipitation > 900 mm, and in medium- and fine-textured soils. Among soil physical health properties, saturated hydraulic conductivity was the most responsive to management practices. Based on this meta-analysis, we conclude that rotations including diverse crop species and grain legumes, managed under conservation tillage are best for improving soil physical health, and thus should be considered when designing and developing sustainable cropping systems that promote soil health, system resilience, and crop productivity. • Increasing crop diversity improved most soil physical health properties. • Grain legumes in cereal-based rotations improved soil physical health properties. • Diversity with conservation tillage enhanced soil aggregation, porosity, and saturated hydraulic conductivity. • Crop diversity improved soil hydrologic properties in regions with mean annual precipitation > 900 mm yr-1. • Rotational diversity over long periods had greater benefits in medium- and fine-textured soils. [ABSTRACT FROM AUTHOR]

Divergent processes in soils affect the pore systems and alter hydraulic, gaseous and thermal fluxes as soon as the internal soil strength (= the precompression stress) is exceeded. Especially the intense changes of the hydraulic flux properties during soil deformation result in retarded soil settlement due to their dependency on time and stress dependent changes in pore water pressure as well as the water saturation degree. These processes depend besides on texture and bulk density especially on aggregation level, but the linkage between changes in effective stress and soil structure in various soil horizons defined by the precompression stress is still not analyzed and is therefore subject of this investigation. In this study, stress strain and pore water pressure data from almost 900 (predrained to −60 hPa) samples from arable top- and subsoil horizons subjected to oedometer compaction tests are evaluated. Among others, hydraulic stress parameters like the effective stress and χ-factor are calculated and linked to the precompression stress values. Results are presented for 6 differently aggregated soil horizons. Ap horizons with a very weak soil structure document no defined soil rigidity due to a reduced functionality of the pore systems and a stress dependent weakening, while especially the soil deformation behavior of sandy Bw horizons is less controlled by the precompression stress and the calculated effective stresses. The E and Bg horizons indicate anthropogenic impacts on structure properties and the related stress-strain behavior. While it could be documented that the enhanced strain coincides with an increase in the calculated χ-factor, it does not coincide in correspondingly enhanced effective stresses due to the non- equilibrated pore water pressure even after 45 h of increasing stress application. We conclude that further investigations are needed to quantify the highly dynamic interactions between the stress dependent hydraulic conductivity / pore water pressure ratio and the impact on the stress affected pore water pressure reequilibration. Furthermore, the contribution of the sorptive potential in soils with more negative initial matric potential on these changes would elucidate also the physico chemical impacts on soil strength more clearly especially under drier soil conditions. • The changes in pore water pressure due to stress application are time dependent. • The χ-factor increases in the virgin compression stress range. • Changes of the effective stress are the more pronounced the weaker the soil. • The hydraulic conductivity affects strain and causes strength decrease or increase. [ABSTRACT FROM AUTHOR]

Studies on how the alteration in the soil pore architecture can influence the permeability of small soil aggregates are still scarce. These aggregates affect the water dynamics mainly at the intra-aggregate pore scale. Thus, investigating the intra-aggregate pore space properties becomes crucial for comprehending the matter and energy transported into the soil. This paper focuses on analyzing the permeability and hydraulic conductivity of small soil aggregates from contrasting tillage systems (no-tillage – NT, minimum tillage – MT, conventional tillage – CT, and secondary forest – F) through synchrotron-based X-ray Computed Tomography. The 3D image segmentation was performed using machine and deep learning strategies. Permeability was measured based on the image-based parametrization of the Kozeny-Carman equation, which is dependent on porosity, hydraulic radius, and tortuosity. The porosity, hydraulic radius, and pore connectivity were not affected by the soil tillage systems at the scale of analysis (aggregates of a few millimeters). Conventional tillage had higher pore tortuosity relative to NT, demonstrating less favorable fluid transport at the aggregate scale. However, only the aggregates under F had significantly higher permeability and hydraulic conductivity relative to NT, MT, and CT. Our results brought new insights into the effects of different tillage systems on the soil structure and their possible impact on water dynamics at the microscale. • Porosity, hydraulic radius, and connectivity were not affected by tillage systems. • Aggregates from conventional tillage had more tortuous pores than from no-tillage. • Aggregates from forest are more permeable and conductive than from tilled soils. • Image segmentation was performed using machine and deep learning strategies. [ABSTRACT FROM AUTHOR]

The idea of the study was to combine the saturation-dependent hydraulic conductivity, K(Se), as intensity parameter with the volume fraction related to the fractional capillary potential for each of the characteristic pore size classes that based on the matric flow potential, φ, and the soil water diffusivity, D(θ). The analysis is focused on the soil hydraulic properties of differently textured soils with differences in the pore size distribution, PSD. The soil-moisture retention, θ(h), and K(Se) as function of the effective saturation were determined with undisturbed samples for each soil profile and horizon and fitted by Mualem–van Genuchten type analytical function. The results indicate a strong linear relationship between φ values and the soil water diffusivity, D(θ), of soils with its volume fractions of macropores (r2: 0.65–0.91), wide coarse pores (r2: 0.55–0.77), and medium pores (r2: 0.83–0.85). The precompression stress, Pc, as mechanical soil strength parameter affects the soil water diffusivity of the chosen datasets especially in the wide coarse pore range (r2: 0.85). The results suggest that the PSD's-related φ and D(θ) values are affected by both textural and structural effects. The soil water diffusivity itself strongly depends on the PSD and is an effective link between soil's intensity and capacity parameter. • Soil water diffusivity is affected by textural and structural effects. • The more humous, the more important is the medium pores range for the soil water diffusivity. • Precompression stress positively affects soil water diffusivity in wide coarse pores range. [ABSTRACT FROM AUTHOR]

A study was conducted to determine the combined effects of three tillage practices and four maize (Zea mays L.)-based cropping systems on physical, saturated, and near-saturated hydraulic properties in a sandy loam soil of North-Western India. Split-plot experimental design was adopted with tillage [conventional tillage (CT), zero tillage (ZT), and permanent raised bed (PB)] as the main plot treatments and intensified crop rotations [Maize (Zea mays L.)-Wheat (Triticum aestivum)-Greengram (Vigna radiata L.) (MWGg), Maize-Chickpea (Cicer arietinum L.)- Sesbania (Sesbania aculeata) (MCpSb), Maize-Mustard (Brassica juncea) -Greengram (MMuGg) and Maize-Maize- Sesbania (MMSb)] as subplot treatments. The saturated and near-saturated soil hydraulic conductivity were derived from steady-state infiltration rates measured using a hood infiltrometer on the surface soil at 0, − 1, and − 3 cm pressure heads. The long-term (10 years) study revealed that the bulk density (BD) of the soil under conservation agriculture (CA) practices (PB and ZT) was significantly (P ≤ 0.05) lower than that in CT practices. The soil BD in the MCpSb cropping system was measured to be the lowest (1.24 g cm−3) among all the cropping systems. The soil aggregate mean weight diameter (MWD) under PB and ZT was determined to be 31% and 27% higher than in the CT treatments. In tillage × cropping systems interactions, the highest MWD was observed in the PB×MWGg. The saturated and near-saturated hydraulic conductivity (K (h)) were estimated to have higher values in CA practices (PB and ZT) than in the CT treatments. In the case of cropping systems, the soil's mean field saturated hydraulic conductivity was estimated to be significantly (P < 0.05) higher under the MWGg, MCpSb, and MMuGg than the MMSb. The present study indicates that conservation agriculture-based crop management with diversified maize-based rotation (MCpSb, MWGg, and MMuGg) could be promising alternatives to conventional tillage practices (CT). Among the cropping system choices, MWGg was more effective in improving the soil's hydro-physical properties in the study area. • Effects of 3-tillage and 4-maize based systems on soil hydraulic properties were evaluated. • Zero tilled permanent beds improved hydraulic properties in all the cropping systems. • Diversified systems had differential impact on near-saturated hydraulic conductivity. • Least near-saturated hydraulic conductivity was observed under Maize-Maize- Sesbania system. [ABSTRACT FROM AUTHOR]

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. • CC effects under NT on soil pore configuration and anisotropy were studied. • The unsaturated functions were determined using the simplified evaporation method. • CC increased structure porosity and affected hydraulic conductivity anisotropy. • The pore size distribution behaved as isotropic regardless soil management. [ABSTRACT FROM AUTHOR]

Land use type can impact soil properties and the characteristics of plant community, which in turn likely affect soil erodibility. The irrational land use induced by the fast conversion from natural forestland to cropland certainly leads to serious soil erosion. Few studies have been conducted to assess the potential effect of land use type on soil erodibility at small watershed scale. The aim of this study was to quantify the effects of six typical land use types on soil erodibility reflected by soil penetration resistance (PR), mean weigh diameter (MWD), mean number of drop impact (MND), slaking rate (SR), soil erodibility of K factor, soil organic matter content (SOM), soil structural stability index (SSI), soil cohesion (Coh), saturated hydraulic conductivity (K s) and an integrated comprehensive soil erodibility index (CSEI) in a small watershed of rolling hill northeast China. The results revealed that MWD , MND , SOM , Coh and K s varied significantly with land use type, with their maximum appeared in forest belt and their minimum occurred in road. The measured PR and SR exhibited an opposite trend. The calculated K factor and SSI were relatively stable or slightly fluctuating with land use type. Significant differences were found in soil texture, bulk density, root mass density and litter mass density between different land use types. CSEI varied extremely with land use type. CSEI of road was the maximum (0.855), while transverse forest belt had the minimum one (0.136). Compared to road, CSEI decreased by 14.3%, 10.8%, 26.5%, 36.9%, 33.3% and 65.7% for maize, soybean, grassland, shrub land, woodland and longitudinal forest belt, respectively. CSEI was significantly decreased and increased linearly with root mass density and bulk density. The results provide insights to understand the differences in soil erosion under different land use types in agricultural small watershed characterized by rolling hills. • Different changes were detected in nine erodibility indicators with land use type. • CSEI varied significantly with land use type, with road and TFB had the largest and smallest CSEI. • RMD and BD were the dominant factors influencing the variation in CSEI with land use type. [ABSTRACT FROM AUTHOR]

Growing livestock populations have intensified the potential for detrimental effects of grazing on grassland soils globally. Grazing management techniques can mitigate these effects but they are livestock-specific and studies on horse grazing are rare. The objective of this work was to compare the effects of rotational grazing (i.e., livestock graze sub-sections of a pasture in sequence) with the continuous approach to grazing on (1) rates of water infiltration (i) at slightly negative pressure potentials (h , −15, −10, −5, −3.5, −1 hPa), (2) saturated hydraulic conductivity (K sat), and (3) bulk density (BD). At a site in New Jersey, USA, one pair of pastures was managed with rotational grazing while another pair experienced continuous grazing. Twelve Standardbred mares were grazed for two years at a stocking rate of 0.52 horses ha−1. Over that period, i (n = 79, each at 5 h values) and BD (n = 154, from depth ranges 0–10 and 30–40 cm) were measured multiple times and K sat values were derived from infiltration measurements. Also, the standardized precipitation-evapotranspiration index (SPEI) was calculated with meteorological data from a nearby weather station. We found that: (1) i values inclusive of the largest pores tested (h = −1 hPa) were greater in rotationally- vs. continuously-grazed fields (geometric means ± GSE were 80.2 ± 1.15 and 42.3 ± 1.13 cm d−1, respectively), (2) K sat values were consistent with those of infiltration at h = −1 hPa but were too variable to isolate the effect of pasture management, and (3) near-surface BD was similar under rotational and continuous grazing (arithmetic means ± SE were 1.32 ± 0.02 and 1.37 ± 0.02 Mg m−3, respectively). Further, during periods of water surplus (i.e., when SPEI was positive), infiltration was strongly reduced in the smaller soil pores (h = −10 and −15 hPa) of the rotationally-grazed fields. This reduction was likely the result of pore colonization and blockage by pasture grass roots growing in these fields. This study suggests that rotational management allows for a larger macropore system than continuous grazing, which could lead to a reduction of water deficits and contribute to the sustainability of grazed ecosystems, with positive effects accruing through time. • Continuous horse grazing can damage soil structure and compress macropores. • Rotational grazing alleviated these effects, allowing for faster macropore infiltration. • Plant roots reduced infiltration during periods of water surplus. • Rotational grazing reduced surface degradation, leading to more sustainable pastures. [ABSTRACT FROM AUTHOR]

Central Santa Fe (Argentina) is a low-gradient region with impaired natural drainage. Extreme rainfall events are increasingly common and cause significant economic losses to agriculture. There is a growing interest in the use of mole drainage as a cost-effective strategy to mitigate such impacts. However, there is no information available that assists with mole drainage design, installation and maintenance, or the field assessment of a system's hydraulic performance. This work was conducted with the dual objective of evaluating the hydraulic performance of an existing mole drains system and validating Hooghoudt's steady-state drainage spacing equation for Mollisols. Three treatments representing different hydrologic conditions were tested; namely: (T1) rainfall of 360-min duration and intensity of 23 mm h-1, (T2) surface water ponding achieved through rainfall intensity of 50 mm h-1 and water depths between 50 and 100 mm, and (T3) similar surface water ponding conditions to treatment T2, but achieved through a rainfall intensity of 65 mm h-1 and either one (T3A) or two (T3B) sequential rainfall events. Following application of water, drainage commenced at 270 and 21 min for T1 and T2, and at 40 and 30 min for T3A and T3B, respectively. Mean drained depths were 1 and 3 mm for T1 and T2, respectively. For T3A, the mean drained depth was about one-third that measured for T3B (2.5 vs. 8.5 mm). Under a dry antecedent soil moisture condition, and rainfall intensity of 23 mm h-1, downward water movement was better described by piston flow. As surface water depth and soil water content increased, water flowed preferentially through the fissures and leg slots created by the mole plough implement at installation. Soil fissuring increased field hydraulic conductivity by factors between approximately three and ten. A 4 m mole drains spacing system was considered to be appropriate for managing excess water in the studied soil type. If the contribution of soil fissures to the field hydraulic conductivity can be accounted for, the Hooghoudt's equation applied to two-layered soils may be used with confidence to help optimise the design of mole drainage systems for Mollisols. Application of this numerical approach, however, will require that the resultant spacing between mole drains be increased by about 30–40 %. Such an allowance will reduce installation costs and will not compromise the hydraulic efficiency of the drainage system. • The hydraulic performance of mole drains was quantified in a Mollisol established to alfalfa. • Hooghoudt's equation can be used to guide the design of mole drainage systems in Mollisols. • Fissuring in moled soil increased field hydraulic conductivity by factors between three and ten. • A 4-m mole drains spacing system was appropriate for controlling excess water. • Mole drainage can improve productivity and resilience of poorly drained Mollisols. [ABSTRACT FROM AUTHOR]

Saturated hydraulic conductivity (K s) is controlled by a suite of soil processes operating at various scales. Little is known about the spatial variability of Ks along a slope and how it is changed through the planting operation process and the specific scales at which the controlling factors function. The objective was to characterize the scale-dependent relationships between K s and various soil processes and thereby to identify the primary controlling factors of K s. On a typical slope transect of 900 m in the black soil region of Northeast China, K s and six soil properties of bulk density (BD), wet-aggregate stability (WAS), surface roughness (SR), soil organic carbon content, sand and clay contents were investigated in an interval of 20 m before and after mechanical sowing in the spring. Statistical correlation analysis, its combination with noise-assisted multivariate empirical mode decomposition (NA-MEMD) and wavelet coherence were employed to examine the interactions between K s and each factor at different spatial scales. The BD was admittedly the dominant factor controlling K s, followed by WAS and SR before and after sowing, respectively. The statistical correlation analysis only detected the significant interactions between K s and BD, whereas the essential influence of WAS and SR were revealed upon frequency component decompositions by NA-MEMD and biwavelet coherency. Applying multiple wavelet coherence, BD was believed adequate in explaining K s variability before sowing, whereas the combination of BD and SR was suggested in the case after sowing. These findings hold important implications for precise K s estimations in the black soil region of Northeast China as well as other similar regions, and also demonstrate the effectiveness of NA-MEMD and wavelet coherence in untangling complex scale-dependent relationships among soil processes. ● K s and six factors were measured before and after sowing along a slope in NE China. ● Scale-dependent relationships were observed between K s and each soil factor. ● BD was admittedly the primary factor, followed by WAS before and SR after sowing. ● Multiple wavelet coherence believed BD was adequate for K s estimation before sowing. ● The combination of BD and SR was selected to explain K s variability after sowing. [ABSTRACT FROM AUTHOR]

Evaluation of soil properties that enable aggregates to resist breakdown from impacting water drops is useful in modeling soil erosion process and tillage of some tropical soils. The effect of applications of poultry manure and spent mushroom wastes on soil properties related to resistance of aggregates of a degraded ultisol to water drops detachment energy (D) in southern Nigeria was studied. The area was under continuous field trials for maize crop. The treatments were: control (PM0SM0), 5 and 10 t ha−1 poultry manure (PM5 and PM10, respectively), 5 and 10 t ha−1 spent mushroom wastes (SM5 and SM10, respectively), and 5 t ha−1 poultry manure plus 5 t ha−1 spent mushroom wastes (PM5 + SM5) applied in seven consecutive years. Experimental design was a randomized complete block design (RCBD) in five replications. Soil samples were analyzed for texture, organic matter, aggregate stability, water retention, bulk density, clay mineralogy and water drop test. Results revealed that seven-year applications of PM5, SM5, SM10, and PM5 + SM5 treatments had significant positive effects on soil structural and hydraulic properties than PM10. However, in comparison to PM0SM0, applications of 10 t ha−1 PM had significant positive effects on these properties. Saturated hydraulic conductivity was 46.6, 35.4, 32.6 and 25.5 cm h−1 in PM5 + SM5, SM10, SM5 and PM10 soils, respectively; compared to 9.6 cm h−1 in PM0SM0. A low aggregate ratio (AR) obtained for PM10 compared to higher values for SM10 and PM5 + SM5 suggest that PM10 in this case had a disaggregating effect on the soil aggregates. Sand content accounted for 81.2% of negative effect on water drop detachment energy (D), while clay content accounted for 86.8% of the positive correlation with D. Only water-stable aggregates (WSA) 0.5–0.25 mm had a significant positive correlation with D (r = 0.661, p < 0.05). Clay dispersion index (CDI) had a highly negative correlation with D (r = − 0.896, p < 0.01). Volumetric water content at FC (− 10 kPa) and PWP (− 1500 kPa) correlated positively with D (r = 0.618, P < 0.05 and r = 0.614, p < 0.05). There was a non-significant positive correlation of Muscovite and Berlinite with D. Significant positive correlations of calcite with D (r = 0.694, p < 0.05), and between mica and D (r = 0.731, p < 0.05), revealed their strong linkage with macro-aggregate stability. It was found that high rates of poultry manure alone could increased erodibility and decreased water retention at FC and PWP, while a combination of poultry manure and spent mushroom wastes could reduce erodibility. These properties could be used to make a quick inference on the resistance of soil aggregates to water drop impact. • Applications of spent mushroom wastes increased larger stable aggregates > 2.0 mm. • Clay content, and OM best predicted aggregate detachment energy D. • Poultry manure increase production of micro-aggregates. [ABSTRACT FROM AUTHOR]

Soil physical degradation is a current problem in Molisols of the Pampas Region under no-tillage (NT), that has been related to over-simplified agricultural systems with scarce or no rotations and long winter bare fallows. Soil physical quality (SPQ) is a key factor of soil health and productivity, as it controls root development and air and water fluxes and storage in the soil, which in turn affect nutrient uptake and plant growth. Cover crops have been proposed as a companion agricultural practice to improve NT performance and SPQ. The aim of this study was to evaluate the effect of the inclusion of winter cover crops in different cropping sequences on capacity and intensity indicators of SPQ in two soils of different texture under NT and to compare it with different traditional crop sequences, including non-agricultural plots. SPQ was evaluated at two different sites, one with a silty loam Argiudoll and the other with a sandy loam Hapludoll. Treatments included plots with and without cover crops, with different summer crop sequences (continuous soybean and corn – soybean rotations). Also, a corn – wheat/soybean rotation with and without pastures was evaluated. All treatments had more than 15 years under the same management. We measured soil organic carbon (SOC), and capacity SPQ indicators (bulk density, total porosity, pore size distribution, air capacity, plant available water, relative field capacity and S index). We also measured dynamic SPQ indicators derived from field infiltration tests (saturated and near saturation hydraulic conductivity, effective macro and mesoporosity, and porosity connectivity indexes for different pore families). On the silty loam Argiudoll, cover crops increased SOC but failed to improve SPQ. This was related to soil physical degradation and the low ability of these soils for structure regeneration. On the sandy loam Hapludoll, cover crops had mixed effects on SOC and pore size distribution, but increased near saturation hydraulic conductivity, in the case of the corn – soybean rotation with cover crops, reaching values similar to those of a natural grassland. • Cover crops increased unsaturated hydraulic conductivity on a sandy loam Hapludoll. • Cover crops did not improve SPQ on a degraded silty loam Argiudoll. • Cover crops had mixed effects on pore system configuration on a sandy loam Hapludoll. • Cover crops increased SOC in soybean but decreased SOC in a corn-soybean rotation. [ABSTRACT FROM AUTHOR]

• Pore size distribution was determined during the first year of cover cropping. • Hydraulic conductivity function was determined with the evaporation method. • Evolution of structural porosity was evaluated and compared with bare fallow. • Introduction of cover crop promotes the creation of a secondary pore system. • Cover crop introduction enhances pore connectivity under no-tillage. Soil degradation is a global problem, threating its conservation and affecting agronomic production. No-tillage (NT) is the main management system for soil conservation world-wide. However, in Argentina, simplification of the crop sequence with high proportion of soybean under NT is a very common practice, leading to soil physical constrains. Crop sequence intensification through the inclusion of cover crops has been reported as an effective tool in the long-term for the enhancement of ecosystems services, improving NT performance. The objective of this work was to follow the evolution of the structural pore domain in the surface layer during the first year after the incorporation of cover crop (cover fallow of barley (Hordeum vulgare L.) and vetch (Vicia sp. L.), CF), as compared with bare fallow (BF), under NT management in a field experiment located in the Argentinean Depressed Pampas Region. Mini-infiltration and evaporation experiments were conducted in undisturbed soil samples (0−5 cm depth) in the laboratory in order to determine the pore size distribution (PoSD) and hydraulic conductivity (K (h)) functions in three different dates (after cover crop seeding, after maize seeding and before maize harvest) in order to follow the changes in soil pore functioning during the first year of cover cropping management. Changes in the soil pore functioning were observed in the short-term after the first cover crop cycle, showing the time-dependence of the hydraulic soil properties. These changes were mainly observed during the maize cycle. Under CF an increment of structural porosity (PS) was observed at the end of the maize crop cycle, while during the fallow period this variable remained relatively constant. K (h) and structural porosity connectivity (Cw) showed a rapid increment under BF during the fallow period, while under CF the increase was more gradual, which could be related to pore clogging and roots decay cycles. From the obtained results, we found that the introduction of cover crops under NT promotes the increment of a secondary pore system related to structural soil porosity during the first year and enhances the unsaturated hydraulic conductivity and pore connectivity, especially at the end of the summer crop cycle. Our results highlight the importance of including cover crops into the crop rotation to improve the structural porosity and its connectivity. As well, the results show the necessity of including the short-term changes in the study of soil hydraulics properties. [ABSTRACT FROM AUTHOR]

[Display omitted] • We compared pore features and morphology before and after compression treatment. • Land subsidence transformed elongated macropores to regular and spherical pores. • Silt and silty clay soils > 100-m deep were the main contributors to land subsidence. • Compression decreased saturated hydraulic conductivity. • Saturated hydraulic conductivity was highly related to pore parameters. The extraction of deep confined groundwater has been widely identified as the main factor leading to land subsidence. However, how soil pore characteristics and morphology may change as a result of land subsidence remains unclear. The objective of this study was to (1) quantify and compare the effects of soil compression due to deep confined aquifer exploitation on soil pore characteristics and morphology and (2) assess the relationships between pore parameters and saturated hydraulic conductivity (K sat). Three kinds of lithology (clay, silt, and silty clay soils) from two 300-m engineering geological boreholes were investigated at natural saturated state (NSS) and complete drainage state (CDS). Seventeen undisturbed soil samples, 70 and 50-mm in diameter and height, respectively, were collected and subjected to steps of uniformly increasing loads in uniaxial confined compression tests to analyze pore characteristics, morphology, and K sat. Keeping the samples in a strain-locked state, pore parameters were assessed after each loading step by using X-ray micro-computed tomography (CT; voxel resolution: 3-μm) images. A hundred CT images were acquired and quantified for each treatment in each soil sample. Soil pore characteristics and morphological parameters including number of pores, number of macropores (diameter (∅) > 1000-μm), number of coarse mesopores (∅ 200–1000-μm), number of fine mesopores (∅ < 200-μm), porosity, macroporosity, coarse mesoporosity, fine mesoporosity, largest pore area, average pore diameter, shape factor, structure model index, degree of anisotropy, and the Euler number were analyzed using ImageJ software. All parameters differed between NSS and CDS treatments, especially in silt and silty clay soils below 100-m depth, and the differences seemed to increase with increasing depth. However, parameter variations were not obvious for clay soil. Furthermore, K sat differed significantly between treatments. The largest pore area, average pore diameter, and regular porosity accounted for 78.2 % of the change in K sat. Thus, the decrease in proportion of elongated macropores favors land subsidence, particularly in silt and silty clay soils below 100-m depth. Efforts such as optimization of groundwater exploitation depth should be made to alleviate and control land subsidence. [ABSTRACT FROM AUTHOR]

• Soil compaction by heavy machines used for transportation and hauling of the pipes. • Excavation and refilling of pipeline trenches result in loss of soil functions. • Restoration of physical soil function requires more than 3 years. The manifold requirements of arable soils e.g. as construction sites for gas pipes or electricity cable hauling can result in extensive stress and deformation processes. It is therefore hypothesized, that external impacts as the load applications by the used construction machinery, the excavation and following refilling activities cause a loss of important soil functions and changes in soil strength. The recovery of soil functions requires efficient amelioration methods in order to re-achieve the site-specific crop yield potential. In course of the gas pipe installation in Eutric Cambisols in the Weichselian glacial till region of Mecklenburg West Pommerania (North Eastern Germany), undisturbed soil samples were taken below the plowed A-horizon in 50 and 80 cm depth in the traffic lanes and refilled pipeline trenches in the construction area as well as in the adjacent arable soils (which were used as references) directly and 3 years after the construction process. Analyses of soil porosity characteristics, air and saturated hydraulic conductivity as well as of soil strength (precompression stress value) indicate a severe loss of soil functions (especially air capacity and hydraulic conductivity) directly after the construction process (refilling of the material) compared to the reference soil. A harmful soil degradation could be verified down to 80 cm depth in the traffic lanes as a consequence of much too heavy machines used for the transportation and hauling of the pipes. After the refilling and leveling process together with the amelioration measures like the application of in total 5 Mg CaO ha−1 and the following cultivation of alfalfa seeded at the surface after the refilling and leveling, the air capacity and air conductivity was improved, but the precompression stress and the saturated hydraulic conductivity only slightly increased during the following 3 years. We conclude that such intense impacts require a longer time period to regain more rigid soil functions in spite of all the supportive amelioration approaches. [ABSTRACT FROM AUTHOR]