Soil Hydrological Properties Research Articles

Regime shift by an exotic nitrogen-fixing shrub mediates plant facilitation in primary succession.

Ecosystem invasion by non-native, nitrogen-fixing species is a global phenomenon with serious ecological consequences. However, in the Mediterranean basin few studies addressed the impact of invasion by nitrogen-fixing shrubs on soil quality and hydrological properties at local scale, and the possible effects on succession dynamics and ecosystem invasibility by further species. In this multidisciplinary study we investigated the impact of Genista aetnensis (Biv.) DC., an exotic nitrogen-fixing shrub, on the Vesuvius Grand Cone (Southern Italy). Specifically, we tested the hypotheses that the invasion of G. aetnensis has a significant impact on soil quality, soil hydrological regime, local microclimate and plant community structure, and that its impact increases during the plant ontogenetic cycle. We showed that G. aetnensis, in a relatively short time-span (i.e. ~ 40 years), has been able to build-up an island of fertility under its canopy, by accumulating considerable stocks of C, N, and P in the soil, and by also improving the soil hydrological properties. Moreover, G. aetnensis mitigates the daily range of soil temperature, reducing the exposure of coexisting plants to extremely high temperatures and water loss by soil evaporation, particularly during the growing season. Such amelioration of soil quality, coupled with the mitigation of below-canopy microclimatic conditions, has enhanced plant colonization of the barren Grand Cone slopes, by both herbaceous and woody species. These results suggest that the invasion of G. aetnensis could eventually drive to the spread of other, more resource-demanding exotic species, promoting alternative successional trajectories that may dramatically affect the local landscape. Our study is the first record of the invasion of G. aetnensis, an additional example of the regime shifts driven by N-fixing shrubs in Mediterranean region. Further studies are needed to identity specific management practices that can limit the spread and impacts of this species.

Spatiotemporal variability of hydrologic soil properties and the implications for overland flow and land management in a peri-urban Mediterranean catchment

Summary Planning of semi-urban developments is often hindered by a lack of knowledge on how changes in land-use affect catchment hydrological response. The temporal and spatial patterns of overland flow source areas and their connectivity in the landscape, particularly in a seasonal climate, remain comparatively poorly understood. This study investigates seasonal variations in factors influencing runoff response to rainfall in a peri-urban catchment in Portugal characterized by a mosaic of landscape units and a humid Mediterranean climate. Variations in surface soil moisture, hydrophobicity and infiltration capacity were measured in six different landscape units (defined by land-use on either sandstone or limestone) in nine monitoring campaigns at key times over a one-year period. Spatiotemporal patterns in overland flow mechanisms were found. Infiltration-excess overland flow was generated in rainfalls during the dry summer season in woodland on both sandstone and limestone and on agricultural soils on limestone due probably in large part to soil hydrophobicity. In wet periods, saturation overland flow occurred on urban and agricultural soils located in valley bottoms and on shallow soils upslope. Topography, water table rise and soil depth determined the location and extent of saturated areas. Overland flow generated in upslope source areas potentially can infiltrate in other landscape units downslope where infiltration capacity exceeds rainfall intensity. Hydrophilic urban and agricultural-sandstone soils were characterized by increased infiltration capacity during dry periods, while forest soils provided potential sinks for overland flow when hydrophilic in the winter wet season. Identifying the spatial and temporal variability of overland flow sources and sinks is an important step in understanding and modeling flow connectivity and catchment hydrologic response. Such information is important for land managers in order to improve urban planning to minimize flood risk.

Are soil–water functions affected by biochar application?

Today biochar is considered a stable-carbon source that is able to improve soil quality. However, although biochar effects on some soil properties are already becoming well known, its impact on complex soil hydrological functions has yet to be better assessed. The main objectives are: (a) to determine the impact of different biochar amendments on important physical and chemical soil properties and (b) to determine whether the origin (biomass or sewage sludge) and pyrolysis technique can change biochar properties and regulate biochar influence on important soil functions, i.e. nutrient release, water sorption, and carbon storage. Six types of biochar produced from different biomass sources (pine, poplar or sludge) and pyrolysis processes (slow, fast or gasification) were applied to a sandy-loam, low-organic-matter, calcareous soil (mean dose: 18g/kg) and incubated in a greenhouse without seeding. Two sampling campaigns, one month and one year after biochar amendments, were performed. The overall impact of biochar, analysed by principal response curves (PRCs), indicated that it could improve or deteriorate soil hydrological properties at different intensities. Soil wettability was modified due to sludge biochar addition to soil by increased water penetration dynamics during the capillary rise process of about 18%. In contrast, water storage as a soil function during soil drying was not affected. Because no differences on aggregate stability were observed between treatments, increments on soil organic carbon could not be related to biochar physical protection caused by aggregate formation or by enhanced aggregate stability. As a result, carbon storage, considered as a soil function provided by biochar, was mainly related to its chemical stability. On the other hand, nutrient flux during soil slaking was improved, increasing nutrient release from soil to water. In terms of biochar properties, an increment of surface wettability of biochar during water drop penetration was observed after one year of its addition to soil, where the mean values of contact angle (CA) decreased 69.5%. This important result suggest that initial biochar hydrophobicity (CA>90°) disappeared after 1year. It was observed that PRC analysis was able to identify important key soil properties that should be monitored when biochar is used as soil amendment. We conclude that the impact of biochar on soil functions depends mainly on biochar feedstock rather than on the pyrolysis technique used during its production. In general, the performance of biochar obtained from sludge and vegetal biomass was markedly different.

High Nitrogen Fertilization of Tobacco Crop in Headwater Watershed Contaminates Subsurface and Well Waters with Nitrate

Our hypothesis was that subsurface and well waters in watershed with shallow, stony soils, steep landscapes, and cropped to tobacco are contaminated by nitrate. Nitrate in soil solution was monitored in (0.20 m) and below (0.5 m) root zone with tension lysimeters, in five transects. Water from two wells (beneath tobacco field and in native forest) used for human consumption was also analyzed for nitrate. Soil bulk density, porosity, and saturated hydraulic conductivity were evaluated. Soil physical and hydrological properties showed great variation at different landscape positions and soil depths. Soil coarse grain size, high porosity, and saturated hydraulic conductivity favored leaching nitrate. Nitrate in soil solution from tobacco fields was greater than in natural environment. Nitrate reached depths bellow rooting zone with values as high as 80 mg L−1in tobacco plantation. Water well located below tobacco plantation had high nitrate concentration, sometimes above the critical limit of 10 mg L−1. Tobacco cropping causes significant water pollution by nitrate, posing risk to human health. A large amount of nitrogen fertilizers applied to tobacco and nitrate in subsurface waters demonstrate the unsustainability of tobacco production in small farming units on steeps slopes, with stony and shallow soils.

Hydrological properties and dynamics of soils on the southern coast of Crimea

A close correlation and linear regression between precipitation, the field capacity, the permanent wilting coefficient, the range of available moisture (it is equal to the difference between the field capacity and the permanent wilting coefficient), and the storage of available water have been revealed under conditions of dry subtropical climate of the Mediterranean type (the Southern Coast of Crimea, State Nikitsky Botanic Garden, 1981–1990) in heavy-loam and light-loam brown soils under the park plantations of introduced subtropical plants. The significant variation in the hydrological properties of soils and elements of their hydrological dynamics in both time and area, as well as the present cyclicity of the latter have been ascertained. To optimize water/soil dynamics on the southern coast of Crimea, it is necessary to irrigate soil additionally at an amount of 416 ± 188 mm/year.

Applying airborne γ-ray and DEM-derived attributes to the local improvement of the existing individual-tree growth model for diameter increment

Airborne gamma-ray data (γ-ray), measuring gamma radiation naturally emitted from the earth's crust has proved useful for predicting the character and distribution of soil properties in forested landscapes. In addition, digital elevation models (DEMs) provide a reliable source of information regarding the hydrological properties of soils. The growth potential of a forest stand is an important parameter in forest management and planning, so that accurate prediction of growth is needed. The present study looked into applying γ-ray data in combination with DEM-derived attributes for improving the existing individual-tree growth model. To adapt the national model to local conditions, the data of 1118 sample trees and 9987 tally located within 197 sample plots in South-eastern Finland were used. Trees were distributed subjectively to reflect the stands' composition and structure. The main aim was to test the suitability of airborne γ-ray in combination with DEM-derived attributes for localizing a general parametric prediction model for the trees' growth (diameter at breast height increment for the period of five years). Linear mixed effect procedures were used to fit models derived from the γ-ray and DEM. Of the various models constructed for comparison purposes, the best result was obtained with broadleaved trees, followed by Scot pine (Pinus sylvestris L.) while Norway spruce (Picea abies L.) revealed little improvement. The improvement was found to be more accurate in less fertile site types (Vaccinum type (VT) and Calluna type (CT)) as well as on mineral soils. The result was found to be effective in reducing the root mean square error (RMSE) and the bias.

The influence of Caragana korshinskii shrub on soil and hydrological properties in a revegetation-stabilized desert ecosystem

Shrub-induced spatial heterogeneity of soil and hydrological properties are common in arid and semi-arid ecosystems. To examine the influence of shrubs on spatial patterns of soil physical, chemical and hydrological properties, the typical sand-fixation species, Caragana korshinskii, was studied in the Shapotou area of the Tengger Desert, China. Miniature cylinder infiltrometers were used to quantify the spatial variations of infiltration rate in the soils, and were installed at 20-cm intervals around the shrubs. Meanwhile, soil samples were collected at 0–5 cm depth every 10 cm to analyse their physical and chemical properties and soil moisture content. The results indicate that the various measured parameters showed a gradational change from sub-canopy to open space. The establishment of shrubs formed obvious “fertile islands” where more soil nutrients collected. The total nitrogen (TN), soil organic matter (SOM), electrical conductivity (EC) and surface soil moisture content decreased gradually from around shrub stems to the interspace. The sand content around shrub stems was significantly higher (p < 0.05), and decreased gradually from the centre towards the outside microsites. The silt and clay contents showed opposite variability characteristics. The variation of soil bulk density was less within 140 cm distance from the stem, and no abrupt change was found at the shrub’s drip line. No significant tendency was found for the soil pH values. The steady infiltration rates declined with increasing stem distance and then tended to be stable, and no abrupt change occurred at the position of the overhead canopy margin. The increase of infiltration rate was rapid nearer to the stem; the variability trend can be fitted by a log-log (power function) model. This study indicated the gradational change in soil and hydrological properties, which was not consistent with the binary division of shrubs into “canopy” and “interspace” zones.Editor Z.W. Kundzewicz

Electromagnetic Conductivity Imaging of Soil Salinity in an Estuarine–Alluvial Landscape

In coastal–estuarine agricultural landscapes, shallow and often saline water tables are problematic because they limit agricultural productivity. To understand the dynamics of rainfall events and tidal influences, natural resource management baseline data need to be collected to describe the heterogeneous nature of the soil and interactions with fluctuating groundwater tables, particularly in areas characterized by coastal acid sulfate soil. Electromagnetic induction instruments are increasingly being used because they measure the apparent soil electrical conductivity (ECa, mS m−1), which is related to soil salinity and hydrologic properties. Our aim was to demonstrate how the ECa data from a DUALEM‐421 can be used in conjunction with inversion software (EM4Soil) to develop electromagnetic conductivity images, which are two‐dimensional cross‐sections of estimates of the true electrical conductivity (σ, mS m−1). We show how the estimates of σ can be related to the electrical conductivity of a saturated soil paste extract (ECe, dS m−1) across an estuarine landscape and situated within Quaternary fluvial sediments adjacent to Rocky Mouth Creek on the far northern coast of New South Wales, Australia. Our results indicate that a good linear relationship (r2 = 0.70) can be established between σ and ECe, and the results reflect the existing soil landscape units.

Thermal analysis as a predictor for hydrological parameters of fire-affected soils

Soil burn severity indexes have been developed to rapidly assess ecosystem damage from vegetation fires and predict associated risks during the post-fire period. In terms of the hydrological impacts of fire, the lack of measurable relationships between the commonly determined parameters and post-fire hydrological responses has limited their potential to predict and mitigate post-fire hazards. This study examines the link between post-fire organic matter characteristics, and main soil physical and hydrological properties (clay content, bulk density, aggregate stability, water retention, water repellency, rainfall–runoff ratio and sediment concentration in runoff) in order to explore the potential use of organic matter characteristics as a proxy for the fire impact on hydrology-related soil properties. Soil samples from five fire-affected burned and unburned control sites in Andisols areas of Tenerife (Canary Islands, Spain), studied previously for hydrological processes, were selected and thermogravimetric (TG) analysis was carried out to evaluate fire impacts on their organic matter composition. The TG data were used to perform simple linear regressions with soil hydrological properties. The organic matter composition was relatively homogeneous among the unburned sites, despite substantial within and between site variability regarding other soil properties examined which simplified the assessment of soil burn severity. The fire led to a decrease in the relative amount of the labile organic matter pool and an increase in the recalcitrant and/or refractory pool depending on study site. The TG data, using 10°C temperature range steps, allowed reasonable prediction of most soil properties and parameters, with R2 ranging from 0.4 to 0.9 and with R2≥0.6 for 6 of the 8 parameters evaluated. The labile pool and the dehydration range positively affected bulk density, aggregate stability, wilting point and water repellency and negatively field capacity and sediment concentration, whereas the refractory pool showed the opposite trend. The recalcitrant pool was unrelated to other soil properties except for clay content and runoff. These results, in conjunction with the simplicity of the TG analysis suggest that, after an initial calibration step to link TG data to site-specific post-fire soil properties, the novel approach introduced in this study could serve as a useful tool for the rapid and cost-effective evaluation of soil burn severity, and anticipated soil hydrological responses after a fire.

Quantifying the influence of biochar on the physical and hydrological properties of dissimilar soils

Evidence suggests that biochar influences soil physical properties, especially soil hydrology, yet relatively little data exists on this topic, especially in relation to soil type or characteristics. This paper presents a novel attempt at analysing the influence of biochar (applied at 0.1, 0.5 and 2.5%) on the physical properties of soil with respect to quantified soil variables. Pot experiments were used to establish the effect of biochar on: bulk density, soil moisture content at field capacity and available water capacity. The aggregate effect of biochar across all soils was significant (P<0.01) for all of the properties. With increasing amount of biochar, changes to bulk density, field capacity and available water were more pronounced. In the 2.5% treatments these changes ranged from −4.2% to −19.2%, 1.3% to 42.2% and 0.3% to 48.4%, respectively. Regression revealed that soil silt content negatively moderated the influence of biochar on field capacity and available water capacity. The results suggested that medium (20tha−1) and high (100tha−1) biochar applications could improve water-holding capacity (by up to 22%) and ameliorate compaction (by up to 15%) and that soils low in silt are likely to be more hydrologically responsive to biochar application.

Simulating the hydrological response of a closed catchment-lake system to recent climate and land-use changes in semi-arid Mediterranean environment

• Water balance model of a closed catchment-lake system was calibrated and evaluated. • A physically based rainfall–runoff model and the energy budget method were used. • Precipitation, land-use and water yield changes in semiarid Mediterranean quantified. • Precipitation was the main driver of the multi-year streamflow variability. • Change from maquis to deforested and altered soil slightly decreased water yield. Lake water levels are sensitive sentinels of changes in the climate and landscape of the broader lake catchment. This means that lakes can be useful for quantifying the effects of these changes on the water yield of a catchment. This study presents a water balance model of a closed catchment-lake system in the semi-arid Mediterranean climate over the last 85 years, with the objective to understand the influence of precipitation change and the conversion from Mediterranean maquis to pasture. Deforestation alters the balance between evapotranspiration and canopy interception, and causes the rapid decay of soil hydrological properties, thus changing the mechanisms of runoff generation. The overall impact of these changes on the water yield has been evaluated for the catchment of the lake. A physically based rainfall–runoff model, combined with the energy budget method for estimating lake evaporation, were used for the lake water balance model. The calibration was carried out with the continuous measurements taken during the period 2008–2013. The reliability was evaluated with the historical lake levels between 1929 and 2008. Simulation errors were small despite the high sensitivity of the water balance model to precipitation, which in the historical period was that of a non-local station. The simulation results show that the balance was influenced by a combination of climate and land-use changes. The 23% decrease in precipitation observed in the last 50-years has resulted in a 72% decrease in average streamflow. The contemporaneous deforestation in 18% of the catchment area resulted in a 13% decrease in streamflow. The main mechanism of runoff generation under the maquis cover was saturated subsurface-flow. At hillslope scale this can eliminate the surface runoff, giving the impression that the water yield is lower than that of deforested hillslopes. However, at the basin scale the effect can also be reversed. The reduction in soil hydraulic conductivity and porosity in deforested and altered soils produces higher soil moisture and perched water-table, which means that there are higher evaporation and percolation losses. As simulated by the hydrological model, these higher losses compensate for the greater throughfall. Thus deforestation gives rise to lower water yield in this semi-arid Mediterranean environment.

Physically based shallow translational landslide susceptibility analysis in Tibo catchment, NW of Portugal

The Northwest of Portugal is a steep slope mountain area where high amounts of rainfall (3,000 mm/year) occur especially on winter, promoting high natural propensity to slope failure, mainly shallow landslides. This article aims to assess shallow landslide susceptibility, in Tibo catchment, Serra da Peneda, North of Portugal, using two physically based models—SHAllow Landslide STABility (SHALSTAB) and Safety Factor (SF)—applying a set of mechanical and hydrological parameters, assessed in situ and laboratory testing of soil samples collected in the field, calibrated by back analysis of landslides inventoried in the study area, as well as accurate topographic information derived from a high-resolution digital elevation model (DEM). The validation of results was made using shallow landslide scars, directly inventoried in the field. Both susceptibility model results were validated by scar concentration (SC) and landslide potential (LP). SHALSTAB model was also validated by minimum log q/T. SHALSTAB predicts 50 % of the area to be on unstable classes (log q/T < −2.5), 77 % of the SC on unstable classes and a LP index of 7 and 4.7 % for the two most unstable classes. By minimum log q/T, SHALSTAB predicts 91 % of the scars to occur on unstable classes. Safety factor predicts 47.99 % of the area as unstable, 79.9 % of the SC for unstable classes, and a LP index on unstable classes of 4.63 and 2.77 % on partially unstable class. For the most unstable classes of both models, the greatest values of LP were between 3.5 and 7 %. The simple physically based models used in this study (SHALSTAB and SF) proved to be effective as shallow landslide susceptibility predictors, being in consequence useful tools for municipal planning on landslide hazards, but their application requires, beyond detailed topographical information, good estimates of the mechanical and hydrological soil properties.

Relationships between soil water repellency and microbial community composition under different plant species in a Mediterranean semiarid forest

Abstract Soil water repellency (SWR) can influence many hydrological soil properties, including water infiltration, uneven moisture distribution or water retention. In the current study we investigated how variable SWR persistence in the field is related to the soil microbial community under different plant species (P. halepensis, Q. rotundifolia, C. albidus and R. officinalis) in a Mediterranean forest. The soil microbial community was determined through phospholipid fatty acids (PLFA). The relationships between microbiological community structure and the soil properties pH, Glomalin Related Soil Protein (GRSP) and soil organic matter (SOM) content were also studied. Different statistical analyses were used: Principal Component Analysis (PCA), ANOVA, Redundancy Analysis and Pearson correlations. The highest concentrations of PLFA were found in the most water repellent samples. PCA showed that microorganism composition was more dependent of the severity of SWR than the type of plant species. In the Redundancy Analysis, SWR was the only significant factor (p&lt;0.05) to explain PLFA distributions. The only PLFA biomarkers directly related to SWR were associated with Actinobacteria (10Me16:0, 10Me17:0 and 10Me18:0). All the results suggest that a strong dependence between SWR and microbial community composition.

Optimizing irrigation efficiency through the consideration of soil hydrological properties – examples and simulation approaches

Climate change is connected with a global increase in the use of irrigation. But irrigation is often practiced on very variable soils with the consequence of overor under-irrigation. The efficiency of irrigation techniques is closely connected with soil hydrological and soil physical interactions in the main root zone. In irrigation practice the deciding and often site-specific soil properties are usually not taken into consideration. This paper will emphasize the importance of soil texture in terms of improving irrigation by summarizing some results of longtime studies about soil water dynamic under the influence of irrigation. Furthermore, the paper presents possibilities of optimizing irrigation on the basis of two simulation approaches. In the first simulation approach a multi-agent-based tool calculates soil specific and corresponding water tensions by using pedotransfer functions. This makes possible a quantification of the need for irrigation and the control of the irrigation system. By integrating the physical concept of soil water potentials, temporal and spatial soil water fluxes are used to schedule dynamic and precision trickle-irrigation. The second simulation approach calculates a field-irrigation with simultaneous consideration of the horizontal variability of soil properties. The irrigation is carried out in a site-specific way with high precision. Both approaches show that precision and soil specific irrigation is accompanied by a significant reduction of irrigation water and an improvement of irrigation efficiency.

IRSeL—An approach to enhance continuity and accuracy of remotely sensed land cover data

Land cover data gives the opportunity to study interactions between land cover status and environmental issues such as hydrologic processes, soil properties, or biodiversity. Land cover data often are based on classification of remote sensing data that seldom provides the requisite accuracy, spatial availability and temporal observational frequency for environmental studies. Thus, there is a high demand for accurate and spatio-temporal complete time series of land cover. In the past considerable research was undertaken to increase land cover classification accuracy, while less effort was spent on interpolation techniques. The purpose of this article is to present a space–time interpolation and revision approach for remotely sensed land cover data. The approach leverages special properties known for agricultural areas such as crop rotations or temporally static land cover classes. The newly developed IRSeL-tool (Interpolation and improvement of Remotely Sensed Land cover) corrects classification errors and interpolates missing land cover pixels. The easy-to-use tool solely requires an initial land cover data set. The IRSeL specific interpolation and revision technique, the data input requirements and data output structure are described in detail. A case study in an area around the city of Neumünster in Northern Germany from 2006 to 2012 was performed for IRSeL validation with initial land cover data sets (Landsat TM image classifications) for the years 2006, 2007, 2009, 2010 and 2011. The results of the case study showed that IRSeL performs well; including years with no classification data overall accuracy values for IRSeL interpolated pixels range from 0.63 to 0.81. IRSeL application significantly increases the accuracy of the land cover data; overall accuracy values rise 0.08 in average resulting in overall accuracy values of at least 0.86. Considering estimated reliabilities, the IRSeL tool provides a temporally and spatially completed and revised land cover data set that allows drawing conclusions for land cover related studies.

Tillage Effects on Crop Yield and Physicochemical Properties of Sodic Soils

AbstractTillage modifies soil structure and has been suggested as a practice to improve physical, hydrological and chemical properties of compacted soils. But little is known about effect of long‐term tillage on physicochemical soil properties and crop yield on sodic soils in India. Our objective was to investigate the effect of different tillage regimes on crop yield (wheat and paddy rice) and physicochemical properties of sodic soils. Two sodic sites under conventional tillage for 5 (5‐YT; 5‐year tillage) and 9 (9‐YT; 9‐year tillage) years were selected for this study. Changes in crop yield and physicochemical soil properties were compared with a control, sodic land without any till history, that is, 0‐year tillage/untilled (0‐YT). Five replicated samples at 0‐ to 10‐cm and 10‐ to 20‐cm soils depths were analysed from each site. In the top, 0‐ to 10‐cm soil depth 5‐YT and 9‐YT sites had higher particle density (Pd), porosity, water holding capacity, hydraulic conductivity, organic carbon, total nitrogen (Nt), available nitrogen (Navail), phosphorus (Pavail) and exchangeable calcium (Exch. Ca++) than 0‐YT, whereas bulk density (Bd), C : N ratio and CaCO3 were significantly lower. Bd, pH, EC and CaCO3 increased significantly with depth in all the lands, whereas Pd, porosity, water holding capacity, hydraulic conductivity, organic carbon, Nt, Navail, Pavail and Exch. Ca++ decreased. We conclude that continuous tillage and cropping can be useful for physical and chemical restoration of sodic soils. Copyright © 2014 John Wiley &amp; Sons, Ltd.

Physical and hydraulic properties of aridisols as affected by nutrient and crop-residue management in a cotton-wheat system

A 5-year cotton-wheat rotation field experiment was conducted on two alkaline-calcareous soils to investigate the impact of integrated nutrient-management and crop-residue incorporation on soil physical and hydrological properties. The nutrient treatments were: T1-farmers' fertilizer use; T2- balanced nutrient management (recommended N, P, Zn. and B from mineral sources); T3-integrated nutrient management, same as T2, except that 75% N was applied from fertilizer and 25% as FYM; and T4 same as T2, except that every alternate year, wheat was substituted by Berseem green manure. All treatments were compared with and without crop residue incorporation. Soil organic matter (SOM) content in both the soils was significantly increased with T2, T3 and T4 as compared with T1, and was increased further where the nutrient-management treatments were applied in combination with crop-residue recycling. Higher increase in SOM content was observed in soil having relatively lower initial SOM (0.61%) than soil having initial 0.80% SOM content. Increased SOM content, in return, decreased soil bulk density, improved macro- and meso-porosity, and enhanced percent recovery of stable aggregates correspondingly. Infiltration rates were 20, 49 and 26% higher with T2, T3 and T4, respectively, over T1 and 64% higher with crop-residue incorporation over crop-residue removal. Positive impacts on soil physical properties were also observed in the sub-soil layers.

Hydrologic properties and leachate nutrient responses of soil columns collected from gypsum-treated fields

Increased availability of flue gas desulfurization gypsum (FGDG) and the recognition of its potential to improve soil–water relationships have stimulated studies of its use on poorly drained soils with high seasonal rainfall, especially on no-tillage (NT) soils. Previous studies have focused on the effects of gypsum on hydrological properties at the soil surface (e.g. infiltration and soil crusting) but little information is available concerning the effects of surface-applied gypsum in profiles of non-sodic NT soils with contrasting drainage classes. To address this lack of information, undisturbed columns from two non-sodic NT soil profiles, characterized as being either moderately well drained or poorly drained, were collected from agricultural fields with historic information regarding number of years of gypsum application (i.e. 0, 4, and 12yr). Alfalfa was planted in the columns and then plant growth, and soil chemical and hydrologic properties were measured. Higher Ca concentrations were found in both gypsum treated soils compared with control (CT) soils (P<0.10). A greenhouse water balance study revealed significantly (P<0.10) greater cumulative drainage (∼60%) associated with the Brookston long-term (LT) gypsum and the Celina short-term (ST) gypsum soil treatments than for the control treatments. This greater drainage response was attributed to Ca redistribution to lower depths and improved soil structure. However, restricted drainage in Celina LT columns was attributed to secondary Ca carbonate precipitation in pores at 60–75cm depth. Leachate samples collected from the columns indicated no element deficiencies that would negatively affect alfalfa growth. Nutrients and trace element concentrations also were within accepted limits for good plant growth and water quality.

Impact of a Recharge Dam on the Hydropedology of Arid Zone Soils in Oman: Anthropogenic Formation Factor

AbstractA hydropedological study was conducted to investigate the impact of the construction of Al-Khoud recharge dam on soil development in a dry region of Oman. The study involved detailed descriptions of pedons, surface and subsurface soil textural analyses, and double-ring and tension infiltrometer tests in areas inside and adjacent to the dam. The reservoir area of this 25-year-old hydraulic structure has rapidly changed due to spatiotemporally variable deposition of sediments from the dammed water and intensive scraping of the silt cake. This resulted in the formation of multiple micro depressions and a nonflat shape of the reservoir bed. The subsurface soils of the bed showed heterogeneity and complex patterns of sediment deposition as a response to the human-induced changes in the soil development, geomorphology, and hydrological properties of the dam area. In most pedons, a sequence of Stokes’ law–generated porous layers indicates ponded conditions of flood events and reservoir filling correlated...

Pore shape and organic compounds drive major changes in the hydrological characteristics of agricultural soils

SummaryA small increase in soil organic matter (SOM) content can change soil hydrological properties from a completely wettable to a partially water‐repellent state. Although considerable research describes hydrophobic compounds as a primary driver of this shift, the influence of pore shape has only been considered in a few studies and none of these has emphasized the role of different carbon compounds. Using a capillary bundle model of non‐cylindrical (wavy) capillaries, we described measured hydrological properties of five agricultural soils that have a small degree of water repellency and textures ranging from coarse sand to heavy clay. To isolate the influence of SOM, it was removed by combustion to provide an SOM‐free treatment. Water and methanol sorptivities quantified infiltration rates and soil‐water wetting angles in packed soil cores. Different cores were sectioned to measure wetting profiles and calculate diffusivity. The results from natural soils were supplemented by measurements carried out on model ‘soils’ consisting of quartz particles (50–200 µm) with four different hydrophobic states. Soil organic matter removal increased water sorptivity from about 60% for a coarse sandy soil (Haplic Arenosol) to about 290% for a heavy clay soil (Haplic Leptosol), corresponding to a decreased apparent wetting angle of 20–30°. Application of the wavy pore model suggests that the apparent wetting angle resulting from SOM removal can be several times smaller than its Young value. Generally, SOM removal increased water diffusivity values by one to two orders of magnitudes. The SOM components having the greatest impact on contact angle were hexanedioic acid and heneicosanoic acid (both hydrophilic) and docosane (hydrophobic).