Soil Hydrological Properties Research Articles

Effect of mineral and edible vegetable oils on physico-chemical and hydrological properties of sandy loam soils in parts of Nigerian basement complex

Effect of mineral and edible vegetable oils on physico-chemical and hydrological properties of sandy loam soils in parts of Nigerian basement complex

An improved drought-fire assessment for managing fire risks in tropical peatlands

Peatlands transformation in Indonesia has caused immense ecological and environmental degradation. Land use conversion has changed this natural carbon sink to a drought- and fire-prone ecosystem. Public awareness to tackle the drought and fire risk in peatlands has led to the development of drought-fire index. Current knowledge states that both climate and hydrology have a strong influence on drought-induced fire in tropical peatlands, yet the role of soil hydraulic properties in controlling the drying of peats remains unclear. This study develops an improved drought-fire index for tropical peatlands, called the Peat Fire Vulnerability Index, by incorporating groundwater and soil water retention information. We tested the new index on two peatland regions in Kubu Raya and Batanghari, Indonesia, to assess fire danger. We monitored daily rainfall, groundwater tables, and soil moisture from 2018 to 2019 on eight stations in the peatlands. Our model was calibrated against the observed drought index of two stations, and the results were verified with actual fire events through daily fire hotspots and fire burned areas in the other six stations. Results showed that soil-hydrological properties influenced the moistening and drying of peats through capillarity. Our model showed good performance in assessing fire danger during the calibration period, as indicated by three employed statistical metrics: the RMSE-standard deviation ratio (RSR = 0.57), Kling-Gupta Efficiency (KGE = 0.81), and percent bias (PBIAS = 1%). For verification, all observed fire events fell in high and extreme fire danger classes predicted by PFVI. Further, our findings revealed the importance of the groundwater table as a threshold of fire events. The high fire danger class was mostly found when groundwater table dropped below 40 cm, and burned areas only occurred when the groundwater table was below 60 cm. These findings suggest that our drought-fire index can be used as a peat fire risk management tool, and its application may minimize fire risks in tropical peatlands.

Alpine shrub had a stronger soil water retention capacity than the alpine meadow on the northeastern Qinghai-Tibetan Plateau

Soil water retention capacity is an essential component of the land surface processes and hydrological cycles. Although the effect of grassland degradation on soil water retention capacity have been well documented, few studies have focused on how soil hydrological properties vary between different vegetation types on the Qinghai-Tibet Plateau (QTP). This study selected three vegetation types: Potentilla fruticosa shrub (PFS), Kobresia pygmaca meadow (KPM), and Kobresia humilis meadow (KHM), and aimed to explore the variations and factors controlling soil water retention capacity across the three types. Results showed that the soil water retention capacity was higher in PFS than in KPM and KHM across 0–40 cm, whereas the 0–30 cm plant available water content was much lower in PFS than in KPM and KHM. Meanwhile, the soil properties within the different soil layers varied significantly between vegetation types. The 0–10 cm clay and silt contents were significantly higher in PFS than in the other two vegetation types, whereas the soil bulk density (BD) was lower in PFS than in KHM and KPM. Furthermore, the 0–50 cm soil capillary porosity (CP) was significantly higher in PFS than in KPM and KHM, except at 0–10 cm. Besides, the 0–10 cm soil organic matter (SOM) was significantly higher in KPM than in PFS and KHM, owing to its highest root biomass. Overall, the soil water retention capacity was most strongly influenced by CP, followed by BD, TP, SOM and root biomass, whereas the soil non-capillary porosity and soil particle size distribution exerted no significant impact on soil water retention capacity. Our results suggested that the alpine shrub had a stronger soil water retention capacity than the alpine meadow.

Improving the soil physical properties and relationships between soil properties in arable soils of contrasting texture enhancement using biochar substrates: Case study in Slovakia

In the agricultural sector, the soil's physical and hydrological properties become a limiting factor in achieving sufficient crop yields. Biochar has emerged as a significant source of organic carbon and a tool for its sequestration and there are identified significant relationships between soil agricultural properties induced by biochar application with that of soil physical and hydrological properties. However, underlying mechanisms for changes in some physical and hydrological properties of the soil are not fully understood due to insufficient data resulting in a poor understanding of the interconnection among properties in biochar substrates amended soils. Therefore, we studied the impact of two different biochar substrates (BS: BS1 – biochar blended with farmyard manure, and BS2 – biochar blended with farmyard manure and digestate) at two rates (10 and 20 t ha−1) combined alone and with additional fertilization (F) on two contrasting soils. The two contrasting soils included a sandy Arenosol, and a loamy Chernozem in south-western Slovakia. The changes in soil physical properties and interrelationships between soil pH, sorption capacity, soil organic matter (SOM), humic substances (HS), and physical properties was regularly monitored in the field for a three-year period (2018–2020). The results showed that biochar substrates had different effects with dependence on soil textures. In sandy soil, BS improved soil properties such as pore size distribution, soil-air content, and water regimes, including water retention capacity (WRC), and soil structure. The most significant effects were determined in the case of BS compared to BS + F, and in the case of 20 than 10 t ha−1 as well as in BS1 than BS2 in sandy soil. In loamy soil, compared to the control, the volume of non-capillary pores (Pnc) values decreased significantly (by 29%) in the BS1 10 t ha−1 treatment, while in the case of BS + F a significant decrease in Pnc was observed after application of both rates of BS1 compared to the fertilized control. For the BS1 + F, compared to the fertilized control, the soil water storage (SWS) increased significantly by 15 and 14% at 10 t ha−1 and 20 t ha−1, respectively. Overall, the soil structure was better in loamy than sandy soil and therefore the effect of BS was not as pronounced in loamy soil as it was in sandy soil. The number of correlations between soil pH, sorption capacity, SOM, HS, and soil physical properties decreased in the following order: loamy soil > sandy soil; BS + F > BS treatments; BS1 > BS2, and at a rate of 20 t ha−1 > at a rate of 10 t ha−1.

The pesticide fate tool for groundwater vulnerability assessment within the geospatial decision support system LandSupport

The protection of groundwater resources from non-point-source pollutants, such as those coming from agricultural practices, is the focus of several European Directives, including the Water Framework Directive and the Pesticide Directive. Besides the environmental goals to be reached by the single EU member state, these directives clearly underline the role of experts in supporting planners and public authorities to fulfil these objectives. This work presents a new web-based, freely-available dynamical tool, named the pesticide fate tool, developed within the geospatial Decision Support system (DSS), LandSupport, for the assessment of groundwater vulnerability, specific for type of pollutant. The tool is based on the extended transfer function model, specifically expanded to consider the transport of reactive solutes, such as pesticides. The work describes the tool implementation for three case studies, with different spatial scales and pedo-climatic conditions: Valle Telesina, IT, Marchfeld, AT, and Zala County, HU. Principal inputs of the tool are: soil physical and hydrological properties, climate, groundwater table depth, type of crops and related pesticides. Results of the model are shown through the LandSupport GUI both as coloured maps, representing the relative concentration of pesticide at the arrival to the water table at the end of the simulation period, and as cumulative charts of the solute arrival at the depth of interest. The three case studies are shown as examples of application of the LandSupport DSS in supporting the Water and Pesticides directives, demonstrating that it represents a valuable instrument for public authorities, environmental planners, as well as agricultural extension services. For example, large differences are shown by soils in filtering the tetraconazole (99.9% vs 76%), a fungicide used in viticulture, or different percentage of arrival (0.32% and 0,01%) to the groundwater table are shown for two herbicides (Tribenuron and Florasulam) largely used to control annual dicotyledonous weeds.

Hydrological soil properties control tree regrowth after forest disturbance in the forest steppe of central Mongolia

Abstract. The central Mongolian forest steppe forms a transition between different ecozones and is as such particularly sensitive to environmental changes. It is commonly affected by disturbances such as logging and forest fires. Intensified drought events aggravate stress on the trees that are anyway at their drier limit in the forest steppe. Climate change increases evapotranspiration and reduces the distribution of discontinuous permafrost, which leads to drier soil conditions. The motivation for this study came about through our previous observation that forest stands show great differences with respect to their recovery after disturbance by fire or logging. Sometimes, no regrowth of trees takes place at all. As water availability is the main limiting factor of forest growth in this region, we hypothesised that differences in soil hydrology control the forest recovery pattern. To test this hypothesis, we analysed soil properties under forests, predominantly consisting of Siberian larch (Larix sibirica Ledeb.), in the forest steppe of the northern Khangai Mountains, central Mongolia. We distinguished the following four vegetation categories: (1) near-natural forest (FOR), (2) steppe close to the forest (STE), (3) disturbed forest with regrowth of trees (DWIR), and (4) disturbed forest showing no regrowth of trees (DNOR). A total of 54 soil profiles were described in the field and sampled for soil chemical, physical, and hydrological analysis. We found a significant difference in soil texture between soils under DWIR and DNOR. Sand generally dominated the soil texture, but soils under DWIR had more silt and clay compared to soils under DNOR. Soil pF curves showed that soils under DWIR had higher plant-available field capacity in their uppermost parts than soils under DNOR. In addition, hydraulic conductivity tended to be higher in the uppermost horizons of soils under DWIR compared to their counterparts under DNOR. Chemical properties of the soils under DWIR and DNOR showed no significant differences. We conclude that the differences in post-disturbance tree regrowth are mainly caused by different soil hydrology. High plant-available field capacity is the key factor for forest recovery under semi-arid conditions. High hydraulic conductivity in the uppermost soil horizons can further support tree regrowth because it reduces the evaporation loss and the competition of larch saplings with grasses and herbs for water. Another important factor is human impact, particularly grazing livestock on cleared forest sites, which often keeps seedlings from growing and, thus, inhibits forest recovery. None of the disturbed sites (DWIR and DNOR) had permafrost. We, thus, conclude that permafrost is no major factor for the post-disturbance tree regrowth pattern, although it generally supports tree growth in the forest steppe by preventing meltwater from seasonal ice from seeping below the root zone, thus increasing the water supply in summer.

Simulated or measured soil moisture: which one is adding more value to regional landslide early warning?

Abstract. The inclusion of soil wetness information in empirical landslide prediction models was shown to improve the forecast goodness of regional landslide early warning systems (LEWSs). However, it is still unclear which source of information – numerical models or in situ measurements – is of higher value for this purpose. In this study, soil moisture dynamics at 133 grassland sites in Switzerland were simulated for the period of 1981 to 2019, using a physically based 1D soil moisture transfer model. A common parameterization set was defined for all sites, except for site-specific soil hydrological properties, and the model performance was assessed at a subset of 14 sites where in situ soil moisture measurements were available on the same plot. A previously developed statistical framework was applied to fit an empirical landslide forecast model, and receiver operating characteristic analysis (ROC) was used to assess the forecast goodness. To assess the sensitivity of the landslide forecasts, the statistical framework was applied to different model parameterizations, to various distances between simulation sites and landslides and to measured soil moisture from a subset of 35 sites for comparison with a measurement-based forecast model. We found that (i) simulated soil moisture is a skilful predictor for regional landslide activity, (ii) that it is sensitive to the formulation of the upper and lower boundary conditions, and (iii) that the information content is strongly distance dependent. Compared to a measurement-based landslide forecast model, the model-based forecast performs better as the homogenization of hydrological processes, and the site representation can lead to a better representation of triggering event conditions. However, it is limited in reproducing critical antecedent saturation conditions due to an inadequate representation of the long-term water storage.

Hydraulic Properties of Forest Soils with Stagnic Conditions

Tree species, e.g., shallow vs. deep rooting tree species, have a distinct impact on hydrological properties and pore size distribution of soils. In our study, we determined the soil hydrologic properties and pore size distribution at three forest stands and one pasture as reference on soils with stagnant water conditions. All sites are located in the Wermsdorf Forest, where historical studies have demonstrated severe silvicultural problems associated with stagnant water in the soil. The studied stands represent different stages of forest management with a young 25-year-old oak (Sessile Oak (Quercus petraea) and Red oak (Q. robur)) plantation, a 170-year-old oak stand and a 95-year-old Norway Spruce (Picea abies) stand in second rotation. We determined the infiltration rates under saturated and near-saturated conditions with a hood-infiltrometer at the topsoil as well as the saturated hydraulic conductivity and water retention characteristic from undisturbed soil samples taken from the surface and 30 cm depth. We used the bi-modal Kosugi function to calculate the water retention characteristic and applied the normalized Young-Laplace equation to determine the pore size distribution of the soil samples. Our results show that the soils of the old stands have higher amounts of transmission pores, which lead to higher infiltration rates and conductance of water into the subsoil. Moreover, the air capacity under the old oak was highest at the surface and at 30 cm depth. There was also an observable difference between the spruce and oak regarding their contrasting root system architecture. Under the oak, higher hydraulic conductivities and air capacities were observed, which may indicate a higher and wider connected macropore system. Our results confirm other findings that higher infiltration rates due to higher abundance of macropores can be found in older forest stands. Our results also demonstrate that an adapted forest management is important, especially at sites affected by stagnant water conditions. However, more measurements are needed to expand the existing data base of soil hydraulic properties of forest soils in temperate climates.

Upland grassland management influences organo‐mineral soil properties and their hydrological function

AbstractLand‐use change acts as a potential moderator of flood risk, affecting vegetation and soil properties and thus influencing the storage and flow of water across landscapes. This study, conducted in northwest England, investigated physical soil properties and their hydrological function using overland flow and soil moisture sensors, for five upland grassland habitats each created through management action. Overland flow was common, occurring up to 60% of the time with longer durations in grassland excluded from grazing with higher density vegetation. Soil moisture varied significantly between grassland habitats, but there was no clear soil moisture threshold for overland flow. Surface soil properties to 5‐cm depth varied significantly between grassland types, with saturated hydraulic conductivity (Ks) ranging across several orders of magnitude from 1.3 × 10−3to 1.5 × 102 m day−1. With shallow soils and a medianKsof 2.4 m day−1, saturation‐excess overland flow was determined as the main driver of flood risk. Landscape management was found to be a significant driver of soil physical and hydrological properties in upland grasslands and therefore should be strongly considered as part of flood management.

Spatial and temporal variability of water table dynamics in an afforested catchment of the Central Spanish Pyrenees

AbstractHuman‐induced afforestation has been one of the main policies for environmental management of farmland abandonment in Mediterranean areas. Over the last decades, several studies have reviewed the impact of afforestation activities on geomorphological and hydrological responses and soil properties, although few studies have evaluated the effects on water table dynamics. In parallel to human‐induced afforestation activities, natural revegetation occurred in abandoned fields and in fields where the intensity of human activity declined, driving the expansion of shrubs. This research addresses the spatial and temporal variability of water table dynamics in a small afforested sub‐catchment located in the Central Spanish Pyrenees. Differences between afforestation (Pinus nigra and Pinus sylvestris) and natural plant colonization (shrubs, mainly Genista scorpius, Buxus sempervirens, and Juniperus communis) and early abandoned meadows (G. scorpius), are analysed in terms of runoff generation and seasonal water table depth dynamics. Precipitation, runoff and water table datasets recorded for the 2014–2019 period are used. Results show a high temporal and spatial variability with large fluctuations in discharge and water table. Groundwater dynamics varied markedly over the year, identifying a wet and dry period with different responses suggesting different runoff generation processes (Hortonian flow during dry and wet periods, and saturation excess runoff during wet conditions). Furthermore, important differences are noted among the various land cover types: (i) in the natural revegetation area (shrubland and meadows) a marked seasonal cycle was observed with short saturation periods during winter and spring; and (ii) in the afforestation areas, the water table dynamics showed a seasonal cycle with a high variability, with fast responses and rapid oscillations. Likewise, the relationship between the depth of water table and hydrological variables was not straightforward, suggesting complex hydrological behaviour.

Forest productivity and associated soil ecosystem services remain altered 15years after mechanized site preparation for reforestation with Pinus radiata

The projected increase in the worldwide demand for forest products over the coming decades may lead to more intensive forest management. This will involve extension of the area of planted forests, increased mechanization and greater pressure to extract timber from sensitive zones such as steep slopes, wet and heavy soils. However, such intensification may place soil protection and ecosystem services provided by forests at risk. In this study, the impacts of mechanized forest site preparation (shearing and ripping) and manual site preparation were evaluated during the first 2.5 years and 15 years after plantation establishment in a soil susceptible to erosion and compaction in a temperate humid climate. Site productivity, soil carbon storage, soil fertility, soil hydrological properties and protection against erosion and run-off were evaluated as ecosystem services provided by forest soils. Soil loss due to manual site preparation was 25 g m−2 yr-1, while annual soil loss ranged from 98 to 3128 g m−2 in sheared sites and from 345 to 4652 g m−2 in ripped sites. However, soil loss was negligible 2.5 years after site preparation. By contrast, soil compaction persisted during 15 years and was significantly higher in mechanically prepared plots than in manually prepared plots. The changes in soil water holding capacity persisted 15 years after site preparation. The available water content was significantly lower in mechanically prepared plots (by shearing and ripping) than in manually prepared plots. During the period 2002–2004, tree height was between 13 and 52 % higher in manually prepared sites than in sheared sites, while in ripped sites tree height was between 91 % higher and 62 % lower than in the manually prepared plots. However, no significant differences in tree height were observed 15 years after site preparation. By contrast, significant differences in the quadratic mean diameter of trees were observed 15 years after site preparation, with tree volumes being highest in manually prepared plots. The findings show that manual site preparation preserves forest ecosystem services such as site productivity and water regulation and can be considered a means of conserving soil and water and a “climate smart” approach in plantation forestry.

Soil structure and soil moisture dynamics inferred from time-lapse electrical resistivity tomography

The semi-arid sagebrush steppe in the western United States faces pressures from the agriculture industry, recreation use, invasive grasses, and a changing climate. A key to facilitating the healthy management of this ecosystem is understanding the distribution and behavior of soil moisture in the vadose zone in both natural and agricultural settings. Within unsaturated environments, soil moisture is spatially and temporally heterogeneous, and changes in porosity and permeability within arid soils complicate characterization of soil hydrologic properties. Importantly, accumulations of ‘caliche’ or pedogenic calcium carbonate in arid soils can greatly limit permeability; however, observing the role that caliche plays in the hydrologic process is difficult because the installation of in situ instruments disturbs the soils and only provides information at a single point. To investigate vadose zone processes on a broad temporal and spatial scale, we installed a 7x8m2 electrical resistivity tomography (ERT) array at the Reynolds Creek Critical Zone Observatory in southwestern Idaho. Existing soil moisture observations show that infiltration is limited to depths less than 60 cm at this site, as compared to at least 90 cm at other sites in the watershed. To capture the seasonal wetting and drying of the soils, as well as the soils’ response to rainfall events, we monitored the site bi-weekly during the spring, summer, and fall of 2015 and 2016. A time-lapse ERT array was placed adjacent to coaxial impedance dielectric reflectometry (CIDR) probes so that the time-lapse ERT data could be referenced to precise measurements of volumetric water content. In addition to the measurements provided by the ERT array and CIDR probes, soil texture analysis and soil profile descriptions from a near-by soil pit show typical arid soil morphology, with accumulations of clays and calcium carbonate in the B horizon. The resulting ERT inversions show the following soil structure: (1) a high-resistivity top layer corresponding with minor amounts of pedogenic calcium carbonate; (2) a low-resistivity intermediate layer at depths corresponding with substantial accumulations (stage IV) of carbonate; and (3) a high-resistivity deep saprolite. The resistivity of the top layer varies seasonally with changes in precipitation, while the intermediate carbonate soil layer does not. This agrees well with the changes in soil moisture with depth measured by the CIDR probes and suggests that the top of the carbonate soil layer limits infiltration. However vertical structure and cracks within the carbonate soil layer create vertical preferential flow paths; resistivity within these flow paths responds to large precipitation events and seasonal changes in soil moisture. This implies that the preferential flow paths are a conduit for soil moisture flow that is not captured by the CIDR probes. From the combined interpretation of the ERT and CIDR we conclude that soil structure and the presence of calcic soil horizons inhibits soil moisture infiltration during both the summer dry months and the winter wet flux period; however, preferential flow paths provide an important vertical connection between the deep and shallow portions of the critical zone.

Changes in soil water retention and content during shrub encroachment process in Inner Mongolia, northern China

Soil water retention is the link between hydrologic processes and ecological patterns, and is one of the vital hydrological properties of soils. However, the influence of shrub encroachment on soil water retention and content remains unclear, and the factors influencing soil water retention and content are also not well understood. Therefore, this study aims to investigate the changes in soil water retention and content during the shrub encroachment process and to reveal their influencing factors. In this study, three states of shrub encroachment were identified according to the percentage of shrub cover. Soil samples of the shrub patches and adjacent interspace grass patches were collected in each state of shrub encroachment. The soil water retention curves of the samples were generated, and the soil water contents of the samples were measured. The results showed that the field capacity (FC) and plant-available water capacity (PAWC) of both shrub patches and interspace grass patches increased during shrub encroachment, which suggests that shrub encroachment has positive effects on soil water retention. The FC and PAWC of the shrub patches were 14.7% and 14.5% higher than those of the interspace grass patches, respectively. The shrub patches were also characterized by higher soil water content and storage than the interspace grass patches. Shrub roots, soil organic matter, and clay content were the three most crucial factors positively affecting soil water retention and content during shrub encroachment process. This study can further our understanding of the ecohydrological effects of shrub encroachment in arid and semiarid grasslands and facilitate related modeling studies.

Effect of Long-Term Soil Management Practices on Tree Growth, Yield and Soil Biodiversity in a High-Density Olive Agro-Ecosystem

Edaphic arthropod communities provide valuable information about the prevailing status of soil quality to improve the functionality and long-term sustainability of soil management. The study aimed at evaluating the effect of plant and grass cover on the functional biodiversity and soil characteristics in a mature olive orchard (Olea europaea L.) managed for ten years by two conservation soil managements: natural grass cover (NC) and conservation tillage (CT). The trees under CT grew and yielded more than those under NC during the period of increasing yields (years 4–7) but not when they reached full production. Soil management did not affect the tree root density. Collecting samples underneath the canopy (UC) and in the inter-row space (IR), the edaphic environment was characterized by soil structure, hydrological properties, the concentration and storage of soil organic carbon pools and the distribution of microarthropod communities. The soil organic carbon pools (total and humified) were negatively affected by minimum tillage in IR, but not UC, without a loss in fruit and oil yield. The assemblages of microarthropods benefited, firstly, from the grass cover, secondly, from the canopy effect, and thirdly, from a soil structure ensuring a high air capacity and water storage. Feeding functional groups—hemiedaphic macrosaprophages, polyphages and predators—resulted in selecting the ecotonal microenvironment between the surface and edaphic habitat.

Soil physical and hydrological properties as affected by a five‐year history of poultry litter applied to a cotton–corn–soybean rotation system

AbstractFew studies were conducted to ascertain poultry litter (PL) and its residual influence on soil physical and hydrological properties. A field study was conducted on a sandy loam soil for 8 yr in corn (Zea mays L.), cotton (Gossypium hirsutum L.), and soybean [Glycine max (L.) Merr.] rotations at Mississippi Agricultural and Forestry Experiment Station in Verona, MS. Poultry litter treatment was applied to the three crops at an average of 7.6 Mg ha–1 yr–1 in the first 5 yr. The inorganic fertilizer treatment was 224 and 100 kg ha–1 yr–1 for corn and cotton. Inorganic P and K fertilizers applied were based on soil analysis, but no synthetic N was applied to soybean. Soil properties and yields were measured in the first year (2015) and third years (2017) after stopping PL application and planting all plots with soybean. Applying PL for 5 yr significantly improved soil aggregate stability by 17%. Infiltration rate and saturated hydraulic conductivity was two to three times greater in soil amended with PL than with inorganic fertilizer. Poultry litter addition significantly increased field capacity and plant available water content by 20%. Those soil properties were not affected by the rotation treatments. Total soil C did not differ between PL and fertilizer treatment. Soybean yield was continuously increased by 8% in 2015 and 11% in 2017 after stopping PL application. Poultry litter application is capable of improving soil physical and hydrological properties, and its residual could sustain soybean yield for 3 yr after stopping applications.

Hydro‐physical soil properties as influenced by short and long‐term integrated crop–livestock agroecosystems

AbstractIntegration of cover crops and livestock (ICLS) in an existing corn (Zea mays L.)–soybean [Glycine max (L.) Merr.] cropping system can be an effective strategy to improve soil physical and hydrological properties. Three on‐farm long‐term (≥30 yr) sites (Sites 1, 2 and 3) and one short‐term (3 yr) experimental site (Site 4) with a randomized block design in eastern South Dakota were selected to evaluate the impacts of ICLS on soil physical and hydrological properties. At Sites 1, 2, and 3, the following long‐term management systems were compared: ICLS (corn/grazing–soybean/grazing–cover crop/grazing), control (CNT, corn–soybean with no cover crop and no grazing), and a grazed pasture (GP). At Site 4, the treatments included ICLS (corn/grazing–soybean/grazing–oat [Avena sativa L.]–cover crop/grazing], cover crop (corn–soybean–oat–cover crop with no grazing), CNT (corn–soybean–oat without cover crop and grazing), and GP. Data showed that soil organic carbon (SOC) was higher by 20–26% and bulk density was lower by 18–37% in long‐term ICLS compared with CNT. Long‐term ICLS also improved soil water retention, macroporosity, infiltration rate, and total porosity compared with the CNT. However, these properties were not affected by short‐term ICLS at Site 4. The GP had the lower soil bulk density and higher SOC and infiltration rate compared with ICLS and the CNT except at Site 4. This study showed that long‐term integration of cover crops and livestock grazing under ICLS can be beneficial in enhancing soil physical and hydrological properties. However, whether such integration improves other soil quality parameters and crop yield requires further investigation.

Fractal and multifractal analysis of soil particle-size distribution and correlation with soil hydrological properties in active layer of Qinghai–Tibet Plateau, China

The soil hydrological properties (HPs) in active layers regulate soil water migration and affect the evolution of permafrost and biogeochemical cycles. There is relatively little understanding of the changes in soil HPs as a result of soil particle-size distribution (PSD) in the permafrost regions of the Qinghai–Tibet Plateau. In this study, different land-cover types, namely alpine wet meadow (AWM), extremely degraded wet meadow (EDWM), alpine meadow (AM), degraded alpine meadow (DAM), alpine steppe (AS), and alpine desert (AD), were used to determine the relationships between soil PSD and HPs. Soil HPs were determined using borehole nuclear magnetic resonance, and soil PSD (0–2 mm) was analyzed using fractal and multifractal theory. The results showed that vegetation degradation caused coarse soil particle accumulation in the root zone, reflected by the soil single-fractal dimension (Dv: 2.12–2.50). The Dv values showed significant positive correlations with soil clay and silt content as well as a negative correlation with sand content. Results from the generalized fractal and singularity spectra suggested an even distribution of soil particles in the root zone of the AWM, AM, and AD sites. Vegetation degradation increased the soil PSD capacity dimension (D0), information dimension (D1), correlation dimension, D1/D0 ratio, and Hölder exponent of order zero. This was indicative of a narrow soil PSD range and non-uniform soil texture in the root zone. Although capillary water dominated the total soil water content in the alpine soils, soil water composition was also dependent on the vegetation type and soil stratigraphic distribution. Soil particle composition and multifractal dimensions were found to be effective parameters for forecasting soil HPs in the non-root zone of alpine soils. However, the presence of vegetation weakens the relationship between soil PSD and HPs. This study contributes to the accurate evaluation of hydrological and biogeochemical cycles in permafrost regions.

Greater, but not necessarily better: The influence of biochar on soil hydraulic properties

AbstractBiochar is recommended as a soil amendment for its positive influence on soil hydrological properties, which results in improved soil fertility and crop yield. Much research in the last decade has been conducted in field and laboratory conditions on the effect of biochar on the hydraulic properties of soil. However, reported results in the literature are substantially inconsistent. Here we performed a meta‐analysis to capture the variations in change in hydraulic properties of arable soils after application of different rates of biochar. The meta‐analysis revealed that high biochar rates (>50 t ha−1) compared to low rates (<20 t ha−1) significantly improved dry bulk density in sandy and clay soils, in field and laboratory experiments. However, field capacity only improved in laboratory experiments on sandy soils. The plant available water, permanent wilting point and saturated hydraulic conductivity did not significantly increase at high rates of biochar application compared to the low rates when applied to different types of soils in both field and laboratory experiments. We discuss possible reasons for this, including hydrophobicity of the biochar with future research directions. We concluded that the current evidence does not support the notion that the application of biochar improves soils' available water capacity.Highlights Meta‐analysis clarifies the influence of biochar on soil hydraulic properties. Biochar addition at higher rates only improves the water holding capacity of sandy soils. Biochar types and pyrolysis temperatures do not influence soil hydraulic properties. The efficiency of biochar may depend on its pore size distribution and hydrophobicity.

Kriging: An advanced Geostatistical Tool to Interpolate the Textural Variation Influences the Yield and Productivity of Tapioca (Manihot esculenta) in Namakkal District, Tamil Nadu, India

Soil texture is a vital variable that reflects a number of soil properties such as Bulk Density, Particle Density, Infiltration Rate, Hydraulic conductivity, Water holding capacity, nutrient storage and availability as well as transport and binding and stability of soil aggregates. For better tuber development in cassava soil texture plays vital role. The main objective of this study is to produce kriged maps (Ordinary kriging map and semivariogram) to interpolate the soil texture for Tapioca growing soils of Paramthy block, Namakkal District at unsampled locations. In this study, nearly 54 surface samples were collected covering 19,149 ha of agriculture land with dominant cultivation of Tapioca. This study helps spatial interpolation of unsampled location of soil texture i.e. sand, silt and clay content which rules the soil physical, chemical and hydrological properties. The average standard error for sand and clay are 0.2 and 0.19 respectively. The results such as provided maps and their associated variance can be used as data source for the development and implementation of further land management and soil water conservation plans in the study area.

Current state of the problem of soil protection and prospect of using humic acids

The article reviews the literature on the state of the problem of protecting the soil cover of the earth. Today, during the period of strong pollution of the lithosphere by technogenic wastes of various nature, leading to soil degradation and erosion, in measures to improve the physical, chemical, hydrological, agronomic and other properties of soils, preference should be given to the least harmless natural raw materials. These include humic acids (HA) and their derivatives, which are good adsorbents, stabilizers and fixers of dispersed systems. The study of the composition of humic acids with various water-soluble polymers and surfactants is another not fully understood area of interdisciplinary nature. Literary search for the works of Kazakh scientists shows the underdevelopment of both the extraction of humic acids and the formation of HA interpolymer complexes (IPC) with polymers and surfactants, as well as their use as fixers, structure formers of soils subject to wind and water erosion. Having large reserves of coal in the republic, a source of humic acids, it is not forgivable not to develop an integrated approach to research on the extraction of HAs, the formation of IPC on their basis and the use of new structure-forming agents to improve the degraded soils of the republic's structures.