Coarse Soil Research Articles

Novel soil-pegged geogrid (PG) interactions in pull-out loading conditions

In current study, large-scale pull-out tests were conducted to examine the behavior of a novel reinforcement system named “Pegged Geogrid” (PG) under pull-out loading condition. Metal pegs were combined with geogrid to enhance resistance to pull-out. Incorporating pegs with geogrids alleviates bolting, welding, clamping, increasing geogrid length or making alterations to the geogrid as recommended by previous researchers. Peg roots are simply inserted/driven through apertures into the soil, nailing the geogrid to the lower and subsequently the upper backfill layers. Effects of soil particle size, normal pressure, peg length, width, and numbers has been evaluated using two sandy and a gravely soil. Results show that inclusion of pegs significantly enhances soil passive resistance contribution to pull-out. Increasing the width and number of pegs, resulted in enhancing passive soil resistance activation in front of the bearing surfaces and thus greater pull-out resistance augmented by soil particle size and normal pressure. Displacements corresponding to maximum pull-out forces gradually improved by peg width and strain distribution along geogrid in the PG system progressively became linear in contrast to the non-linear distribution in the conventional soil-geogrid (NG) system. Normal pressure was more influential on enhancing pull-out resistance in coarser soil.

Effect of Land Use Change on Soil Physico-chemical Characteristics in Sungai Batang, east part of Maninjau caldera

Land-use change from the forest to others will affect the soil’s physicochemical properties. The research was conducted to identify soil physicochemical properties affected by land-use change in Sungai Batang, the east-south part of Maninjau caldera. The research used a survey method from which soil was sampled at four different types of land use (forest, bushland, mixed garden, and paddy soil) at 0-30 cm depth with three replicates. The results show that the soil in Sungai Batang was still developing. It was indicated by coarse soil texture (clay loam to sandy clay loam). Land-use change from the forest to other uses has altered some soil physicochemical properties. It increased soil bulk density and decreased total soil porosity, permeability rate, SOM content, and total-N. However, there was an increase in soil characteristics, especially soil P-availability, CEC, Ca- and Na-exchangeable . While the soil pH (H2O), K-and Mg-exchangeable stayed the same. In general, land use changed from forest to other use, mostly farming land degraded physicochemical characteristics of the soil derived from volcanic materials in Sungai Batang. That was mainly due to the decrease in SOM content.

Patterns in Cheatgrass Abundance in Foothills Grasslands in Montana

Cheatgrass (Bromus tectorum L.) is an invasive, exotic annual grass that exerts substantial negative ecological and economic influence in many of the ecosystems it invades. Cheatgrass has been extensively studied in the Great Basin region of North America where most precipitation comes in winter and early spring and the vegetation consists primarily of cool-season species and cespitose graminoid growth forms. However, much less research has been performed in the northern Great Plains region where precipitation comes primarily in spring and summer, supporting a mixture of cool and warm season plant species and both sod-forming and cespitose graminoid growth forms. In order to better understand cheatgrass ecology in the northern Great Plains region, we modeled cheatgrass abundance in relation to disturbance, vegetation, and site characteristics in two grassland locations in Montana. Multimodel inferences based on large generalized linear mixed-effects regression were used to identify variables important in predicting cheatgrass abundance. Our results suggest that cheatgrass appears to favor droughty site conditions associated with either coarser soil textures, shallower soils, or south-facing aspects. However, cheatgrass can exhibit extremely high abundances on more productive sites if disturbance creates an opportunity for invasion. Across all sites, it appears that soil disturbance can generate increased cheatgrass abundance and land management that promotes robust and vigorous vegetation and maximizes spatial and temporal niche occupancy should be encouraged to limit cheatgrass invasion and expansion.

Pipe Dreams: The Effects of Stream Bank Soil Pipes on Hyporheic Denitrification Caused by a Peak Flow Event

AbstractPeak flow events in gaining stream/river channels cause lung model hyporheic exchange with the banks (bank storage), which fosters beneficial reactions as polluted channel water cycles through riparian groundwater. Soil pipes are common along stream/riverbanks, and enhance exchange, yet their effect on reactions such as denitrification is unknown. We used MODFLOW with the Conduit Flow Package to simulate lung model exchange during a peak flow event in a section of stream bank/riparian soil with soil pipes, and MT3D‐USGS to estimate nitrate transport and denitrification. We varied soil matrix hydraulic conductivity (K) and first‐order reaction constant (k), as well as soil pipe density, length, and height above the initial channel water surface elevation (H). The addition of soil pipes enhanced stream bank (riparian) denitrification relative to banks without pipes, e.g., a 76% increase due to adding a single 1.5 m pipe. Denitrification increased linearly with pipe density but exhibited nonlinear trends with other parameters. Sensitivity analysis revealed length and density to be most influential. Soil pipe enhancement of denitrification was governed by hyporheic volume in most cases in our study. Exceptions included (a) coarse soil (K = 10−3 m/s) and (b) low k and H > 0. Scaling our results to the stream corridor scale estimated that five soil pipes per m cumulatively induced 3% nitrate removal along a 1 km reach. Overall, soil pipes enhanced advection of nitrate into the banks, and also increased residence times of that nitrate under certain conditions, which together enhanced denitrification. This enhancement has implications for excess nitrate management in watersheds.

Influence of Organic and Mineral Fertilizers on Soil Organic Carbon and Crop Productivity under Different Tillage Systems: A Meta-Analysis

The intensive use of mineral (M) fertilizers may cause harm the environment via leaching or greenhouse gas emissions, destroy soil fertility as a consequence of loss of soil organic matter, and, due to their high price, they are economically unviable for producers. It is widely accepted that organic (O) fertilizers may deal with pressing challenges facing modern agriculture, even if farmers need to improve their knowledge for applying in fertilization programs. A meta-analysis approach has been adopted to evaluate the effects on soil organic carbon (SOC) and crop yield of O fertilizers, applied alone or in combination with mineral fertilizers (MO) under conventional (CT), reduced (RT), and no-tillage (NT) regimes. The analysis was performed in different climatic conditions, soil properties, crop species, and irrigation management. Organic fertilizers have a positive influence in increasing SOC compared with M (on average 12.9%), even if high values were observed under NT (20.6%). The results highlighted the need for flexible and environment-specific systems when considering organic fertilization subjected to different tillage regimes. Similarly, MO application showed a better crop yield response in CT and RT under coarse soils when compared with M fertilizer applied alone (on average 13.4 and 12.7%, respectively), while in medium-textured soils, CT and RT yielded better than NT under O fertilizers (9.5 and 11.2 vs. 2.5%, respectively). Among the crop species, legumes performed better when O fertilizers were adopted than M fertilizers (on average 15.2%), while among the other crop species, few differences were detected among the fertilization programs. Under irrigated systems, RT and NT led to higher productivity than CT, especially under MO treatments (on average 9.2 vs. 3.4%, respectively). The results highlighted the importance of the environmental and agronomical factors and how their understanding could affect the impact of these conservation farming practices on crop productivity to improve the sustainability of the farming system in a specific region.

Wind erodibility of Arenosols and its driving factors during sand dune fixation: A wind tunnel experiment

Determining the wind erodibility (WE) of Arenosols (sandy soils) and its driving factors is imperative for evaluating wind erosion in desert ecosystems. Here, we performed a wind tunnel experiment to determine the WE of mobile sand dunes (MSDs), semifixed sand dunes (SSDs), and fixed sand dunes (FSDs) in the Ulan Buh Desert, and revealed its relationships with soil properties, such as soil organic matter (SOM), calcium carbonate (CaCO3), and particle size distribution (PSD). Moreover, we investigated the variation in WE subject to wetting-drying processes with diverse soil moisture gradients. We suggested taking the derivative of the wind erosion content of wind speed (K) to indicate WE, which offered a fresh approach to infer WE from observations in wind tunnel experiments. The results indicated that: compared with the MSDs and SSDs, the FSDs performed better in terms of vegetation cover and soil properties, but the variation in WE was not statistically significant among different sand dunes. WE correlated positively with SOM and CaCO3 and correlated negatively with coarse soil particles. In addition, WE was substantially affected by the wetting process. The critical relative moisture content needed to hamper wind erosion ranged from 3.4 to 3.7% (gravimetric) in the Ulan Buh Desert. However, the variation in WE was not statistically significant between before and after the wetting-drying process. The results of our study are expected to provide new insights into the wind erosion of Arenosols.

Estimating particle-size distribution from limited soil texture data: Introducing two new methods

Most soil databases present the mass fractions of sand, silt, and clay particles without detailed primary particle-size distribution (PSD). In the present paper two simple methods are introduced to estimate the PSD using the fractions of sand, silt, clay, and very coarse sand. A total of 504 soil samples with different texture classes from different regions, i.e., southern Iran (245), south-eastern Brazil (116), and UNSODA database (143) were used. PSD of the Iranian and Brazilian soil samples were determined using a combination of wet-sieving and sedimentation (hydrometer for Iranian and pipette for Brazilian soils) approaches and that of the others extracted from UNSODA database. We developed two new methods including very coarse sand-dependent (VCS-D) and very coarse sand-independent (VCS–I) to predict PSD of the soils. PSD were also predicted using the revised Skaggs method (R-Skaggs) and compared with the measured ones. Both VCS-D and VCS-I approaches with very simple equations accurately estimated full range of PSD in a wide range of the fine to medium textured soils)clay, clay loam, loam, silty clay, silty clay loam, silt loam, and silt texture classes). Accuracy of predictions was slightly lower in coarse textured soils (sandy clay, sandy clay loam, sandy loam, loamy sand, and sand textures) than that of the other texture classes. For these coarse textured soils, it is strongly recommended that the fraction of particles between 0.05 and 2 mm diameters be estimated using the VCS-D or VCS-I methods and the fraction of particles between 0.002 and 0.05 mm diameters be estimated using the R-Skaggs method. The R-Skaggs method could only predict the PSD in the soils with nearly 25–60% sand content, accurately. Whereas, the new proposed methods could predict full range of PSD with high accuracy (NRMSE <10%) in soils with sand content less than 53%. Overall, the proposed methods could accurately predict full range of PSD curve by using only the content of primary soil particles in nearly 73% of soil classes in texture triangle. • New methods (VCS-D and VCS-I) proposed to estimate particle-size distribution (PSD). • The methods are very simple and accurate to estimate PSD from limited texture data. • The methods are very accurate to estimate PSD in 73% of soil texture triangle. • The methods excellently estimate PSD in fine and medium textured soils. • The methods were more accurate than R-Skaggs in fine and medium textured soils.

Wintertime haze and ozone at Dinosaur National Monument

ABSTRACT Dinosaur National Monument (DINO) is located near the northeastern edge of the Uinta Basin and often experiences elevated levels of wintertime ground-level ozone. Previous studies have shown that high ozone mixing ratios in the Uinta Basin are driven by elevated levels of volatile organic compounds (VOCs) and nitrogen oxides (NOx) from regional oil and gas development coupled with temperature inversions and enhanced photochemistry from persistent snow cover. Here, we show that persistent snow cover and temperature inversions, along with abundant ammonia, also lead to wintertime haze in this region. A study was conducted at DINO from November 2018 through May 2020 where ozone, speciated fine and coarse aerosols, inorganic gases, and VOCs were measured. Three National Ambient Air Quality Standards (NAAQS) ozone exceedances were observed in the first winter, and no exceedances were observed in the second winter. In contrast, elevated levels of particulate matter were observed both winters, with 24-h averaged particle light extinction exceeding 100 Mm−1. These haze events were dominated by ammonium nitrate, and particulate organics were highly correlated with ammonium nitrate. Ammonium nitrate formation was limited by nitric acid in winter. As such, reductions in regional NOx emissions should reduce haze levels and improve visibility at DINO in winter. Long-term measurements of particulate matter from nearby Vernal, Utah, suggest that visibility impairment is a persistent issue in the Uinta Basin in winter. From April through October 2019, relatively clean conditions occurred, with average particle extinction of ~10 Mm−1. During this period, ammonium nitrate concentrations were lower by more than an order of magnitude, and contributions from coarse mass and soil to haze levels increased. VOC markers indicated that the high levels of observed pollutants in winter were likely from local sources related to oil and gas extraction activities. Implications: Elevated ground-level ozone and haze levels were observed at Dinosaur National Monument in winter. Haze episodes were dominated by ammonium nitrate, with 24-h averaged particle light extinction exceeding 100 Mm−1, reducing visual range near the surface to ~35 km. Despite elevated ammonium nitrate concentrations, additional gas-phase ammonia was available, such that any increase in NOx emissions in the region is likely to lead to even greater haze levels.

Postfire Seedling Establishment of Desert Peach (Prunus fasciculata) and Joshua Tree (Yucca brevifolia) from Simulated Seed Caches in the Mojave Desert

Desert rodents in the western USA cache enormous numbers of seeds. Seed caches represent a reliable, although highly variable, source of seedling recruitment for numerous desert plants. Prefire caching of refractory seeds (i.e., those capable of forming persistent seed banks) is an important source of postfire seedling recruitment, but it is likely that prefire caches of short-lived seeds also may contribute to postfire regeneration. The primary objective of this study was to quantify seedling recruitment from artificial caches of 2 species with short-lived seeds planted after a stand-replacing wildfire in a singleleaf pinyon (Pinus monophylla) forest. I investigated the survival of 180 artificial caches of Yucca brevifolia and Prunus fasciculata. Caches were composed of 2, 4, or 8 seeds. Also, because soils of the burned area have unusually high coarse fragment volumes (59%), I examined, in greenhouse trials, how soil coarse fragment volumes (CFVs) impacted seedling establishment of these 2 species from caches. In greenhouse trials, the number of P. fasciculata seedlings increased with increasing CFVs. In contrast, Y. brevifolia seedling numbers decreased with increasing CFVs. In field transects, 17% of cached P. fasciculata seeds produced seedlings, whereas 12% of Y. brevifolia seeds recruited seedlings in the first year postfire. The advantage of P. fasciculata in greenhouse CFV trials was not replicated in field seedling recruitment. Seedling mortality over the first 3 years postfire was not statistically different among the 3 cache sizes for either species, nor did seedling sizes differ significantly by cache size and survey date. I conclude that, although the overall recruitment from postfire caches was low (12%–17%), prefire caches of short-lived seeds probably recruit postfire seedlings, but only in specific circumstances.

Estimation of the Radon Risk Under Different European Climates and Soil Textures.

Radon is a radioactive gas produced from the natural radioactive decay of uranium and is found in almost all rocks and soils. In confined places (e.g., dwellings, workplaces, caves, and underground mines), radon may accumulate and become a substantial health risk since it is considered the second most important cause of lung cancer in many developed countries. Radon risk assessment commonly considers either field or estimate values of the radon concentration and the gas permeability of soils. However, radon risk assessment from single measurement surveys to radon potential largescale mapping is strongly sensitive to the soil texture variability and climate changes, and particularly, to the soil water content dynamic and its effect on soil gas permeability. In this paper, the gas permeability of soils, and thus, the estimation of radon risk, is studied considering the effect of three different climates following the Köppen classification and four soil textures on soil water content dynamics. This investigation considers the CLIGEN weather simulator to elaborate 100-year length climatic series; Rosseta 3 pedotransfer function to calculate soil hydraulics parameters, and the HYDRUS-1D software to model the dynamics of water content in the soil. Results reveal that climate strongly affects gas permeability of soils and they must be considered as an additional factor during the evaluation of radon exposure risk. The impact of climate and texture defines the soil water content dynamic. Coarse soils show smaller gas permeability variations and then radon risk, in this case, is less affected by the climate type. However, in clay soils, the effect of climate and the differences in soil water content derive in gas permeability variations between 100 and 1,000 times through an annual cycle. As a result, it may cross the boundary between two radon risk categories. Results deeply confirm that both climate and texture should be compulsory considered when calculating the radon exposure risk and in the definition of new strategies for the elaboration of more reliable geogenic radon potential largescale maps.

Root System Scale Models Significantly Overestimate Root Water Uptake at Drying Soil Conditions.

Soil hydraulic conductivity (ksoil) drops significantly in dry soils, resulting in steep soil water potential gradients (ψs) near plant roots during water uptake. Coarse soil grid resolutions in root system scale (RSS) models of root water uptake (RWU) generally do not spatially resolve this gradient in drying soils which can lead to a large overestimation of RWU. To quantify this, we consider a benchmark scenario of RWU from drying soil for which a numerical reference solution is available. We analyze this problem using a finite volume scheme and investigate the impact of grid size on the RSS model results. At dry conditions, the cumulative RWU was overestimated by up to 300% for the coarsest soil grid of 4.0 cm and by 30% for the finest soil grid of 0.2 cm, while the computational demand increased from 19 s to 21 h. As an accurate and computationally efficient alternative to the RSS model, we implemented a continuum multi-scale model where we keep a coarse grid resolution for the bulk soil, but in addition, we solve a 1-dimensional radially symmetric soil model at rhizosphere scale around individual root segments. The models at the two scales are coupled in a mass-conservative way. The multi-scale model compares best to the reference solution (−20%) at much lower computational costs of 4 min. Our results demonstrate the need to shift to improved RWU models when simulating dry soil conditions and highlight that results for dry conditions obtained with RSS models of RWU should be interpreted with caution.

Estimating soil organic carbon and nitrogen stock based on high-resolution soil databases in a subtropical agricultural area of China

Quantifying soil organic carbon stock (SOCS) and total nitrogen stock (STNS) of the agriculture soils in China is crucial for predicting the future of global climate change and planning agricultural management practices. However, most of existing studies were based on relatively coarse soil databases, leading to large discrepancies in the SOC and STN estimates. The present study was conducted in Changting County of Fujian Province in China, covering an area of 29,375ha. A high-resolution soil database at a county-scale of 1:10,000 was employed to analyze the SOC density (SOCD) and STN density (STND) under different soil groups and land use types. Results indicated that the mean SOCD and SOCS for the surface layer (0–15 cm) were 2.93 ± 0.38 kg C m−2 and 861 Gg, respectively, and those for STND and STNS were 0.37 ± 0.06 kg N m−2 and 108 Gg, respectively. The SOCD and STND showed significant disparities among soil groups and land use types. We also compared the SOCD, SOCS, STND and STNS estimated from a coarser 1:1000,000 soil database, which was the most detailed soil database at the national scale, with the estimates in this study. The relative deviations in estimating SOCD and STND by soil groups from the coarser database were 8.1% and 60.6%, respectively, which could be primarily attributed to the assignment errors of soil attributes and polygon area variations in the coarse-scale soil database. Moreover, we found that the dominant factors determining SOCD were topographic and climatic factors (e.g. elevation and mean annual precipitation), while farming practices (e.g. N fertilizer application and irrigation conditions) as well as elevation were more important for STN estimates. Further, the deviations of STN estimates from the coarse- and fine-scale soil database were higher than those of the SOC estimates because: (1) The topographic and climatic factors had slight effects on STND from coarse- and fine-scale soil database while significantly affected SOCD; and (2) STN estimates tended to be more easily influenced by anthropic farming practices (e.g. significant irrigation conditions and N fertilization application) in the coarse-scale database than that in the fine-scale database. Therefore, a high-resolution soil database may improve the accuracy of SOC and STN assessment, especially for STN assessment, and the application of finer soil databases is a critical step for estimating SOCS and STNS at national and even global levels, and thus for accurately assessing regional C budget.

Seasonal phosphorus and nitrogen cycling in four Japanese cool-temperate forest species

PurposeIn plant-soil systems, phosphorus partitioning during the annual cycle related to nitrogen partitioning remains largely unknown. The present study aims at assessing the soil-plant P allocation patterns of four tree species along four phenological stages and its relationship with tissues and soil N concentrations.MethodsCryptomeria japonica, Larix kaempferi, Fagus crenata and Robinia pseudoacacia trees were selected to sample coarse roots, sapwood, foliage, litter and soil during four phenological stages where total and Olsen extractable P and nitrogen content were measured respectively.ResultsIntra- and inter plant tissue nitrogen correlated well with phosphorus during the four phenological stages, especially root nitrogen. Fagus and Robinia were phosphorus limited, Larix was nitrogen limited and Cryptomeria co-limited. All species reabsorbed phosphorus and nitrogen from foliage prior to leaf abscission and stored nitrogen in roots and sapwood. Phosphorus storage was solely found in sapwood of Robinia. Soil dissolved ammonium correlated positively with nitrogen reabsorption efficiency during the green leaf stage, while single soil nutrient variables did not correlate with phosphorus reabsorption efficiency.ConclusionsPlant tissues nitrogen partitioning correlated well with their respective phosphorus partitioning and the increase of soil NH4+ correlated positively with nitrogen reabsorption efficiency, regardless of tree species during the green leaf stage. The results of this study show the intricate relationship that exists between nitrogen and phosphorus in the soil-plant continuum as well as the tree species specific internal cycling of these nutrients.

Estimating cation exchange capacity and clay content from agricultural soil testing data

Clay content and the ability to reversibly retain cations affect many essential chemical and physical properties of soil, such as pH buffering and carbon sequestration. Cation exchange capacity (CEC) and base saturation are also commonly used as criteria in soil classification. However, determination of CEC and particle-size distribution is laborious and not included in routine soil testing. In this study, pedotransfer functions including soil test cations (STCat; Ca2+ + Mg2+ + K+), pH and soil organic carbon (SOC, %) as explanatory variables were developed for estimating CEC, titratable acidity (TA; H+ + Al3+) and clay content (clay, %). In addition, reference values for potential CEC and its components were determined for Finnish mineral and organic soils. The mean of potential CEC extracted by 1 M ammonium acetate at pH 7.0 ranged from 14 (range 6.4−25) in coarse soils to 33 (21−45) cmol(+) kg-1 in heavy clay soils, and from 42 (24−82) in mull soils to 77 (25−138) cmol(+) kg-1 in peat soils. The average CEC of clay and SOC were 27 and 160 cmol(+) kg-1, respectively. Titratable acidity occupied 53% and around 40% of the CEC sites in organic and mineral soils, respectively, evidencing that it is a prominent component of the potential CEC in these predominantly acidic soils. STCat, pH and SOC explained 96% of the variation in potential CEC. STCat and pH can be used in estimating the clay content especially for soils containing over 30% clay. In coarse textured soils, in contrast, SOC hampers the STCat based estimation of clay content.

Impacts of summer and winter conditions on summer river low flows in low elevation, snow-affected catchments

Reduced snow storage has been associated with lower river low flows in mountainous catchments, exacerbating summer hydrological droughts. However, the impacts of changing snow storage on summer low flows in low-elevation, snow-affected catchments has not yet been investigated. To address this knowledge gap, the dominant hydroclimate predictors of summer low flows were first identified through correlation analysis in 12 tributary catchments of the St. Lawrence River in the Canadian province of Quebec. The correlation results show that summer low flow is most sensitive to summer rainfall, while maximum snow water equivalent (SWE) is the dominant winter preconditioning factor of low flows, particularly at the end of summer. The multivariate sensitivity of summer low flow to hydroclimate predictors was then quantified by multilevel regression analysis, considering also the effect of catchment biophysical attributes. Accumulated rainfall since snow cover disappearance was found to be the prime control on summer low flow, as expected for the humid climate of Quebec. Maximum SWE had a secondary but significant positive influence on low flow, sometimes on the same order as the negative effect of evapotranspiration losses. As a whole, our results show that in these low elevation catchments, thicker winter snowpacks that last longer and melt slower in the spring are conducive to higher low flows in the following summer. More rugged and forested catchments with coarser soils were found to have higher summer low flows than flatter agricultural catchments with compacted clayed soils. This emphasizes the role of soils and geology on infiltration, aquifer recharge and related river baseflow in summer. Further climate warming and snowpack depletion could reduce future summer low flow, exacerbating hydrological droughts and impacting ecosystems integrity and ecological services.

DOWNSCALING OF SMAP SOIL MOISTURE PRODUCT BY DATA FUSION WITH VIIRS LST/EVI PRODUCT

Abstract. Soil moisture is an essential variable of environment and climate change, which affects the energy and water exchange between soil and atmosphere. The estimation of soil moisture is thus very important in geoscience, while at same time also challenging. Satellite remote sensing provides an efficient way for large-scale soil moisture distribution mapping, and microwave remote sensing satellites/sensors, such as Soil Moisture and Ocean Salinity (SMOS), Advanced Microwave Scanning Radiometer (AMSR), and Soil Moisture Active Passive (SMAP) satellite, are widely used to retrieve soil moisture in a global scale. However, most microwave products have relatively coarse resolution (tens of kilometres), which limits their application in regional hydrological simulation and disaster prevention. In this study, the SMAP soil moisture product with spatial resolution of 9km is downscaled to 750m by fusing with VIIRS optical products. The LST-EVI triangular space pattern provides the physical foundation for the microwave-optical data fusion, so that the downscaled soil moisture product not only matches well with the original SMAP product, but also presents more detailed distribution patterns compared with the original dataset. The results show a promising prospect to use the triangular method to produce finer soil moisture datasets (within 1 km) from the coarse soil moisture product.

DUS(Soil)—A Framework for Developing a Minimum Data Set of Soil Health Indicators and Management Guidelines for Farmers

Soil health information is still not widely used in decision making in agriculture. One of the reasons is the lack of a simple and effective method for selection of soil health indicators that have direct relevance to management decisions. A framework for soil health indicators selection and developing location-specific management practices that improve soil health are presented. The framework involves selection of a minimum data set of soil health indicators based on &amp;lsquo;DUS(Soil)&amp;rsquo; criteria. In this framework &amp;lsquo;D&amp;rsquo; represents Distinctness (indicators representing distinct functional soil processes), &amp;lsquo;U&amp;rsquo; represents Utility (amenability for amelioration of the status of the indicator or altering its impact through management practices) and &amp;lsquo;S&amp;rsquo; represents Simplicity (amenability for measurement in the field/small laboratories using simple protocols). This study also outlines a method for developing management guidelines for farmers based on the status of the selected soil health indicators. This involved classifying the status of each of the indicators into three classes. Thereafter, taking cognizance of the agroecological context, suitable field management schedules were developed for each class of the indicators, based on literature and local expert knowledge. The use of this framework was demonstrated by developing management guidelines for a coarse textured soil with optimum pH, low soil carbon, poor in water stable aggregates (highly slaking), optimum porosity and poor in soil macro fauna in Mandla district, Madhya Pradesh, India. The study showed that the framework is flexible, generic as well as simple and is useful to develop site-specific management guidelines logically, to overcome the soil quality constraints.

Exploring the clogging process in coarse soil deposits in a dam foundation

Exploring the clogging process in coarse soil deposits in a dam foundation

Effect of fly ash- and polyacrylamide-consolidated soil layer on A. splendens growth in a desert in North China

Vegetation restoration is an important part of effective desertification control. Consolidated soil layer (CSL) formed by mixing coal fly ash (FA), dry anionic polyacrylamide (PAM) granules, and sandy soil can increase the resistance to wind erosion of the soil. This study further investigated the effect of CSL on vegetation recovery on the sandy land in the Ulan Buh Desert, North China. FA and PAM were applied into the 0–0.3 m depth sandy soil layer at varying application rates to form CSLs (viz. T1 (5%FA + 0.05%PAM), T2 (5%FA + 0.1%PAM), T3 (10%FA + 0.05%PAM), T4 (10%FA + 0.1%PAM), T5 (15%FA + 0.05%PAM), and T6 (15%FA + 0.1%PAM)) where Achnatherum splendens (Trin.) Nevski (A. splendens) was planted. The results showed that the moisture content of T3 and T4 was consistently higher than that of untreated sandy soil (CK) along the 0.1–0.2 m depth soil layer, which was attributed to the increased water holding capacity of sandy soil by FA and PAM via alteration of coarse soil texture by fine-sized FA particles and binding of soil particles by PAM as well as the formation of soil surface crust. As a result, the growth traits of A. splendens including average height, tillers number, and leaf-area coverage were promoted in CSLs during the one-year growth period, with the most distinctly improved final growth traits noted in T4 and T6. The eight-month field observation found that the resistance to wind erosion of CSL with A. splendens cover was significantly improved than that of CK, and the wind erosion rate decreased with increasing FA application rate. The improvement in the resistance to wind erosion of CSL was attributed to the pozzolanic action and filling effect of fine FA particles and adhesive action and inter-particle binding of PAM. A. splendens cover was demonstrated to effectively protect the CSL from being eroded by wind in the field.

The Effects of Rainfall, Soil Type and Slope on the Processes and Mechanisms of Rainfall-Induced Shallow Landslides

Landslides are a serious geohazard worldwide, causing many casualties and considerable economic losses every year. Rainfall-induced shallow landslides commonly occur in mountainous regions. Many factors affect an area’s susceptibility, such as rainfall, the soil, and the slope. In this paper, the effects of rainfall intensity, rainfall pattern, slope gradient, and soil type on landslide susceptibility are studied. Variables including soil volumetric water content, matrix suction, pore water pressure, and the total stress throughout the rainfall were measured. The results show that, under the experimental conditions of this paper, no landslides occurred on a 5° slope. On a 15° slope, when the rainfall intensity was equal to or less than 80 mm/h with a 1 h duration, landslides also did not happen. With a rainfall intensity of 120 mm/h, the rainfall pattern in which the intensity gradually diminishes could not induce landslides. Compared with fine soils, coarser soils with gravels were found to be prone to landslides. As the volumetric water content rose, the matrix suction declined from the time that the level of infiltration reached the position of the matrix. The pore water pressure and the total stress both changed drastically either immediately before or after the landslide. In addition, the sediment yield depended on the above factors. Steeper slopes, stronger rainfall, and coarser soils were all found to increase the amount of sediment yield.