Differences In Soil Texture Research Articles

Seedbed consolidation and surface sealing for soils of different texture and soil organic carbon contents

The soil structure near the surface of agricultural soils changes with season mainly by land management together with climatic and biological factors. Quantitative analysis of post-tillage changes in soil structure and related hydraulic properties are necessary for evaluating and improving models of soil hydrological and transport processes. The objectives of this study were to quantify changes in soil seedbed structure induced by rainfall and drainage and to estimate the eff ;ects of soil texture and SOC on these changes. We collected samples from the harrowed layer of twenty-six fine to coarse textured Swedish mineral soils. Air-dried soil was placed in cylinders (5 cm high, diameter 5 cm) and exposed to simulated rainfall (5 mm h−1 for 4 h) and drainage (−50 cm pressure potential) cycles in the laboratory. We used X-ray tomography to quantify changes in pore networks in a thin surface layer and in the whole cylinder. Infiltration rates at -5 cm pressure potential were measured using a mini disc tension infiltrometer on replicate air-dried samples and on the samples included in the consolidation experiments at the final state. Total imaged specific pore volumes generally decreased from initial to final state and pore size distributions were shifted towards larger proportions of below image resolution pores (< 80 μm). There was a strong positive correlation between clay content and changes (i.e. final state-initial state) in the specific volume of pores <80 μm. Soils with high clay content and soil organic carbon (SOC) content often have strong aggregates that resist changes. Nevertheless, both clay and SOC contents were negatively correlated with the changes in specific imaged pore volume. These results highlight the importance of swelling, which is largely controlled by clay content, for seedbed consolidation. In line with previous studies, when excluding coarse textured soil, the changes in surface porosity were negatively correlated with silt content. Changes in infiltration capacity were not significantly correlated with any basic soil properties. Our results suggest that shrinking-swelling should be a central part in any model for seedbed consolidation.

Changes in the physico-chemical properties of topsoil in a landslide-affected area (western part of the Transylvanian Basin, Romania)

Landslides determine increases and decreases in specific soil compounds which is affecting soil fertility. The recovery of soil fertility is a long process and may be used as an indicator of the landslide age and can contribute to the management plan of the affected area. In order to add to data about soil properties affected by landslides, the current study focuses on a young and shallow landslide from the western part of the Transylvanian Depression. Soil samples were analysed from a physico-chemical point of view (pH, organic matter – OM, total organic carbon – TOC, major cations, and iron content) in two places, at between 0 and 60 cm depth (inside and outside the landslide). The results obtained showed lower values of pH inside the landslide, low values of TOC and rock fragments in both places studied (inside and outside the landslide) and no differences in soil texture between disturbed and undisturbed soil. The ammonium, magnesium and calcium content was higher outside the landslide, the sodium level was slightly higher outside the landslide, while the potassium concentration was higher inside the landslide. This study offers new data regarding recovery of soil fertility and highlights the importance of gaining knowledge on soil properties of relevance to future measures to increase the fertility of agricultural soils.

Native Perennial Plants Colonizing Abandoned Arable Fields in a Desert Area: Population Structure and Community Assembly

In recent years, the phenomenon of abandonment of arable fields has increased in Saudi Arabia due to low soil fertility, drought, low rainfall, high levels of evapotranspiration, soil salinization, and low level of groundwater. We evaluated the effect of agricultural land abandonment on soil properties, perennial vegetation composition, and population structure in the Al-Kharj region, Saudi Arabia. A total of 11 perennial plant species belonging to 9 families and 11 genera were detected in the different abandoned fields of the study area. Four plant communities were identified after the application of the detrended correspondence analysis (DCA) ordination. The indicator species were (1) Seidlitzia rosmarinus—Zygophyllum hamiense, (2) Traganum nudatum—Seidlitzia rosmarinus, (3) Traganum nudatum—Prosopis farcta, and (4) Calligonum comosum—Pulicaria undulata. Results of the soil analysis showed significant differences in soil texture, pH, salinity, and nutrient content among the four recognized plant communities. Demographic analysis indicated that populations of Zygophyllum hamiense and Calligonum comosum tended to be either inverse J-shaped or positively skewed which may have indicated rapidly-growing populations with high reproductive capacity. Conversely, the size–frequency distribution of Traganum nudatum, S. Rosmarinus, and Prosopis farcta was approximately symmetrical (i.e., bell-shaped). The present study sheds light on the necessity of managing abandoned agricultural fields for restoring and improving rangelands with native species that are adapted to the local conditions such as low water demand.

Cultivation impacts on soil texture during oasis expansion in Xinjiang, Northwest China: Wind erosion effects

To explore the cultivation effects on soil texture at local and regional scales during the expansion of oases, a field survey combined with remote sensing monitoring was conducted in the arid desert regions in Xinjiang, Northwest China. We evaluated possible changes by comparing cultivated and uncultivated lands in 2019 with paired reference lands from the Second National Soil Survey of China. The results showed that the clay content and the silt content in cultivated land increased with cultivation years ( p < 0.05), while the sand content decreased. A comparison of the clay plus silt content between 2019 and the late 1970s revealed the accumulation of fine particles in the center of oases and the removal of fine particles at their edges. Our results also demonstrate that sand content increased in the newly reclaimed land, the uncultivated land at the edge of the oases, and the sandy land. A comparison of 15 paired reference samples indicated that in most plots, clay content and silt content in croplands are higher than in adjacent uncultivated lands, although some plots showed a decreasing trend, implying that agricultural cultivation dose not always increase fine particles. We conclude that the initial difference in soil texture before reclamation and reclamation history jointly result in differences in soil texture between cultivated and adjacent uncultivated lands. During oasis expansion, the reclamation of the sandy land can reduce wind erosion, suggesting that appropriate agricultural reclamation and conservation measures can mitigate the adverse effects of changes in soil texture.

Soil nutrient variation along a shallow catena in Paracou, French Guiana

Tropical forests are generally considered to stand upon nutrient-poor soils, but soil nutrient concentrations and availabilities can vary greatly at local scale due to topographic effects on erosion and water drainage. In this study we physically and chemically characterised the soils of 12 study plots situated along a catena with a shallow slope in a tropical rainforest in French Guiana both during the wet and the dry season to evaluate seasonal differences. Soils along the catena were all Acrisols, but differed strongly in their water drainage flux. Over time, this differential drainage has led to differences in soil texture and mineral composition, affecting the adsorption of various nutrients, most importantly phosphorus. The more clayey soils situated on the slope of the catena had higher total concentrations of carbon, nitrogen, phosphorus and several micronutrients, while extractable nutrient concentrations were highest in the sandiest soils situated at the bottom of the catena. We found that carbon, nitrogen and extractable nutrients all varied seasonally, especially in the surface soil layer. These results are interesting because they show that, even at the local scale, small differences in topography can lead to large heterogeneity in nutrient concentrations, which can have large impacts on plant and microbial community organisation at the landscape level.

Impact of Water Stress on Microbial Community and Activity in Sandy and Loamy Soils

Prolonged drought and extreme precipitation can have a significant impact on the activity and structure of soil microbial communities. The aim of the study was to assess the impact of drought length on the dynamics of mineral nitrogen, enzyme activities and bacterial diversity in two soils of different texture (sand and silt loam, according to USDA classification). An additional objective was to evaluate the effect of compost on the alleviation of soil microbial responses to stress conditions, i.e. alternating periods of drought and excessive soil moisture. The pot study was carried out in a greenhouse under controlled conditions. Compost was added at an amount equal to 3% of soil to the sandy soil, which was characterised by a significantly lower water retention capacity. Specific levels of water stress conditions were created through application of drought and soil watering periods. For each soil, four levels of moisture regimes were set-up, including optimal conditions kept at 60% of field water holding capacity, and three levels of water stress: The low level—2 week period without watering; the medium level—1 month drought period followed by watering to full but short-term soil saturation with water; and the high level—2 month drought period followed by full and long-term saturation with the same total amount of water, as in other variants. The soil water regime strongly modified the activities of dehydrogenases and acid and alkaline phosphatase, as well as the bacterial diversity. Loamy soil exhibited greater resistance to the inhibition of soil enzymatic activity. After irrigation, following both a 1 month and 2 month drought, the enzyme activities and nitrification largely recovered in soil with a loamy texture. Drought induced substantial shifts in the functional diversity of bacterial communities. The use of such C substrates, as carboxylic and acetic acids, was strongly inhibited by water deficit. Water deficit induced changes in the relative abundances of particular phyla, for example, an increase in Acidobacteria or a decrease in Verrucomicrobia. The study clearly proves the greater susceptibility of microbial communities to drought in sandy soils and the important role of exogenous organic matter in protecting microbial activity in drought periods.

Modelling the Movement of some Mobile Hydrocarbons Below the Crop Rooting System Using Small-Scale Lysimeters with Undisturbed Soils

The presence of hydrocarbons in groundwater represents a serious risk of disease. This study tests the timing, concentration and amount of BTEX oil components during the oil vertical movement though small-scale lysimeters containing undisturbed soils of different textures and by simulating the fate of oil spills under continuous water application. Three soil types were studied: a sandy-textured, highly permeable Eutric Arenosol, AR-eu, a loamy/sandy-loamy textured Haplic Chernozem, CH-ha, and a loamy-clayey/clayey textured, swell-shrink, Luvic-Chernic Phaeozem, PH-ch-lv. Crude oil was applied as a batch application using an equivalent of 5 g oil /100 g of dry soil for a 0.02 m height in each lysimeter of the three soils studied. After oil-penetration into the soil, tap water was applied on a daily basis above the lysimeters according to infiltration rate. The breakthrough curves of the BTEX compounds show that the highest mobility in the investigated sandy AR-eu soils and loamy CH-ha soils was found for benzene followed by toluene. The other hydrocarbons only showed a limited mobility. There was no leachate from the swell-shrink PH-ch-lv soil. Soil texture and permeability thus play an important role in the movement of BTEX compounds toward the groundwater. After applying an amount of water of 200% from the total soil porosity, or an equivalent of 800-850 mm of precipitation, the leaching process did not end and there still is a leaching potential remained for these hydrocarbons. The highest amount leached per mm of effluent was also for benzene followed by toluene. There were highly significant, direct correlations between the amounts of the hydrocarbons leached and the cumulative effluent volume. The swell-shrink soils are still an effective barrier to hydrocarbons` movement toward groundwater. The BTEX aromatic hydrocarbons leached from the soils, if reach the groundwater, represent sources of pollution with severe risks for human health.

Performance of Wheat in Five Soils of Different Textures under Freshwater and Wastewater Irrigation

This study investigated the effects of five soils of different textures on wheat cultivation under irrigation with freshwater (FW) and municipal wastewater (WW). The experimental design was a split-plot with irrigation water quality as main factor and soil texture as sub-factor in three replications. These factors respectively comprised 2 and 5 treatments. Soil texture significantly (p£0.05) influenced plant height, leaf area index (LAI), spike length, number of grains per spike, above ground dry matter (ADM), grain yield, straw yield and biomass yield of wheat in most cases both under FW and WW irrigation. The harvest index (HI) of wheat responded significantly under FW irrigation only. Under FW, treatment T5 (silt loam) produced the highest grain yield (4.2 t ha–1) followed by T3 (loam-1) (3.1 t ha–1); the lowest yield (2.0 t ha–1) was in the control treatment, T1 (loamy sand). Under WW, treatment T2 (sandy loam) produced the highest grain yield (5.0 t ha–1) followed by T4 (loam-2) (4.5 t ha–1) both of which are statistically similar; the lowest yield (3.4 t ha–1) was in the control treatment. Treatments T2 and T4 provided the highest straw yield (5.6 t ha–1) and treatment T2 provided the highest biomass yield (10.6 t ha–1), both under WW; both T2 and T4 produced invariant biomass yields. Compared to other treatments, T2 and T4 gave statistically similar but significantly higher water productivity with respect to straw and grain yields. The lowest water productivity was in treatment T1 under both water qualities. The results of this study provided sound criteria in selecting suitable lands for wheat cultivation based on irrigation water quality, specifically in alluvial plains where soil texture is prone to high variations. Also, the observed facts of improved productivity of lower quality coarse-textured soils due to addition of easily available and inexpensive clay would provide guidance to bring unproductive sandy soils under production by clay amendments.

How do soil microbial communities respond to fire in the intermediate term? Investigating direct and indirect effects associated with fire occurrence and burn severity

Fires transform soil microbial communities directly via heat-induced mortality and indirectly by altering plant and soil characteristics. Emerging evidence suggests the magnitude of changes to some plant and soil properties increases with burn severity, but the persistence of changes varies among plant and soil characteristics, ranging from months to years post-fire. Thus, which environmental attributes shape microbial communities at intermediate time points during ecosystem recovery, and how these characteristics vary with severity, remains poorly understood. We identified the network of properties that influence microbial communities three years after fire, along a burn severity gradient in Sierra Nevada mixed-conifer forest. We used phospholipid fatty acid (PLFA) analysis and bacterial 16S-rDNA amplicon sequencing to characterize the microbial community in mineral soil. Using structural equation modelling, we applied a systems approach to identifying the interconnected relationships among severity, vegetation, soil, and microbial communities. Dead tree basal area, soil pH, and extractable phosphorus increased with severity, whereas live tree basal area, forest floor mass, and the proportion of the ≥53 μm soil fraction decreased. Forest floor loss was associated with decreased soil moisture across the severity gradient, decreased live tree basal area was associated with increased shrub coverage, and increased dead tree basal area was associated with increases in total and inorganic soil nitrogen. Soil fungal abundance decreased across the severity gradient, despite a slightly positive response of fungi to lower soil moisture in high severity areas. Bacterial phylogenetic diversity was negatively related to severity and was driven by differences in nutrients and soil texture. The abundance of Bacteroidetes increased and the abundance of Acidobacteria decreased across the severity gradient due to differences in soil pH. Overall, we found that the effects of burn severity on vegetation and soil physicochemical characteristics interact to shape microbial communities at an intermediate time point in ecosystem recovery.

Phosphate Organomineral Fertilizer Usage Compared to Mineral Phosphate in Corn Cultivation

Corn has great relevance for agribusiness as it is used in human and animal food, besides the energy matrix. The objective of this study was to assess the leaf content of macro and micronutrient, accumulation of primary macronutrients, production components and productivity with the application of pelleted organomineral fertilizer in different doses compared to mineral fertilization, in two soils of different textures in the corn crop. Two trials were conducted in the municipality of Uberl&amp;acirc;ndia-MG-Brazil: one located near the highway BR 452 km 141, at the coordinate 18&amp;deg;55&amp;prime;26&amp;Prime;S, 48&amp;deg;09&amp;prime;36&amp;Prime;W, clay soil. The other at km 640 of BR 365, at coordinate 18&amp;deg;54&amp;prime;05&amp;Prime;S, 48&amp;deg;25&amp;prime;20&amp;Prime;W, sandy soil. A randomized block design with five replications was used, with five doses of organomineral fertilizer (40, 60, 80, 100 and 120% of the recommended dose of P2O5 for corn) and an additional with 100% of the recommendation of mineral P2O5, total of six treatments and 30 plots. The results showed that, with the exception of phosphorus leaf content, yield in the sandy texture and the number of grains per row in the clay texture, there was no difference between the doses of phosphate organomineral and did not differ from the mineral. Thus, phosphate organomineral is as efficient as mineral for phosphorus supply.

Biochar as a sustainable alternative to açaí waste disposal in Amazon, Brazil

The açaí palm (Euterpe oleracea Mart) is native to the floodplains of central and South America and is cultivated in Brazil for its berries, which are considered to be a ‘superfood’. The waste açaí fiber and seeds obtained after fruit processing pose a challenge since they remain unutilised despite being an abundant waste by-product of açaí processing.This leads to a build-up of waste, regular dumping and environmental management challenges. Here we examine the potential use of açaí seed biochar as a soil conditioner. The biochar was produced from waste seeds in a handmade kiln, incorporated into two soils of different textures and then compacted in volumetric rings with a hydraulic press. The samples were kept in a greenhouse for a 270-day incubation period. After this, the samples were evaluated for their soil physical and chemical attributes. Nine months after the application of the açaí seed biochar, soil physical properties were not affected, except for the soil aggregate size distribution, for which the highest dosage resulted in a larger weighted average diameter. However, biochar increased phosphorus, potassium and magnesium contents, and reduced the aluminum content, which was reflected in an increase of the base saturation and a reduction in aluminum saturation. Therefore, within a relatively short time period, the biochar was found to improve soil chemical quality more so than soil physical properties, thus offering potential as a sustainable solution to manage açaí waste in the Amazon region.

Evaporation from soils of different texture covered by layers of water repellent and wettable soils

Water repellent soils are able to channel water deep into the soil profile by fingered flow, minimising water storage in the water repellent top layer where water is most susceptible to evaporation. To date, the effect of water repellent or wettable surface layer on evaporation from wet sublayer has only been reported for coarse materials, and an increase in water repellency led to a greater delay in water evaporation. The objective of this study was to assess the effect of water repellent vs. wettable top layers with different thickness on water evaporation from coarse and fine texture subsoils that were pre-moistened. Clay loam soil samples were taken from Pinus pinaster woodland of Ciavolo, Italy, and sandy soil samples from Pinus sylvestris woodland of Sekule, Slovakia. Evaporation from soil samples was determined from the loss of weight in laboratory conditions. Water in the clay loam soil from Ciavolo was held for a longer period due to slower evaporative loss than in the sandy soil from Sekule, and the impact of the water repellent layer on the loss rate over time is related to its thickness. Over 550 h, about 90% of the initial stored water was evaporated from the uncovered clay-loam soil sample from Ciavolo. In the same time, the 0.3, 1, and 2 cm-thick duff layers, respectively, saved about 23, 34, and 58% of water from evaporation, and evaporation of 90% of water took over 780, 1100, and 1450 h. It means that the clay loam soil cover with the 0.3, 1, and 2 cm-thick duff layers resulted in prolonging the evaporation by 10, 23, and 37.5 days, respectively. As to the sandy soil from Sekule, 98% of water was evaporated from the uncovered soil sample over 240 h. In the same time, the 0.3, 1, and 2 cm-thick water repellent soil layers, respectively, saved about 7, 45, and 59% of water from evaporation, and evaporation of 98% of water took over 330, 606, and 774 h. It means that the sandy soil cover with the 0.3, 1, and 2 cm-thick water repellent soil layers resulted in prolonging the evaporation by about 4, 15, and 22 days, respectively. It can be concluded that water repellent surface layers, created by pine trees, are able to delay evaporation significantly for both coarse and fine textured soils, which may be particularly beneficial for plants during hot and dry periods in summer.

AGA-SVR-based selection of feature subsets and optimization of parameter in regional soil salinization monitoring

ABSTRACTSalinization is a major eco-environmental threat in arid and semi-arid regions. Machine learning combined with salinization-related factors extracted from satellite images and Digital Elevation Model (DEM) data to monitor salinization is popular in recent years. The hyper-parameters referring to the parameters prior to fitting the model to the data and the features referring to the factors used for model establishment are vital to modelling accuracy, while the optimization of the above two was not given enough attention. In this study, we proposed a novel approach for simultaneously identifying the input features and hyper-parameters of Support Vector Regression (SVR) based on Adaptive Genetic Algorithm (AGA) for quantitative assessment of salinization in Weigan-Kuqa river delta oasis (Wei-Ku oasis), Sangong River Basin, and Qitai oasis of Xinjiang. First, a total of 41 salinization-related factors of 7 categories were extracted from Landsat 5 TM and DEM data. In each sub-region, the Pearson’s correlation analysis was developed between Soil Salt Content (SSC) and salinization-related factors, and the factors significantly correlated with SSC were arranged in descending order of absolute correlation coefficient to form the Candidate Feature Variables (CFVs). The ration of Coefficient of Determination (R2) and Root Mean Square Error (RMSE) multiplied by 1000 was considered as the fitness function of Genetic Algorithm (GA) and AGA. The CFVs and hyper-parameters were combined together and binary coded, then brought into the AGA and GA for simultaneous feature selection and hyper-parameters optimization of SVR, and established salinization monitoring models (AGA-SVR, GA-SVR). In order to highlight the importance of identifying the input features and hyper-parameter to modelling accuracy, the GS-SVR with all the CFVs as input was established using Grid Search (GS) algorithm to optimize the hyper-parameters. Finally, the salinization maps predicted by three models were compared. The results showed that the sensitivity of salinization-related factors to SSC varied with regions, and 25, 16, 24 salinization-related factors were selected as CFVs in Wei-Ku oasis, Sangong River Basin, and Qitai oasis, respectively. Compared with GS-SVR, the GA-SVR and AGA-SVR got more accurate salinization monitoring with fewer features as input, and fitness generated by AGA-SVR increased by 25.968% in Wei-Ku oasis, 25.159% in Sangong River Basin, 27.568% in Qitai oasis, respectively. Both nature and human factors lead to salinization. The difference of Land Surface Temperature (LST) was the main contributor of different salinization between Wei-Ku oasis of southern Xinjiang and the other two sub-regions of northern Xinjiang. The differences in soil texture, irrigation methods, and livestock carrying capacity were the main factors resulting in differences of salinization in Qitai oasis and Sangong River Basin. Our study shows that the proposed approach can provide technical support for accurate salinization monitoring.

Change in Soil Particle Size Distribution and Erodibility with Latitude and Vegetation Restoration Chronosequence on the Loess Plateau, China.

Analyzing the dynamics of soil particle size distribution (PSD) and erodibility is important for understanding the changes of soil texture and quality after cropland abandonment. This study aimed to determine how restoration age and latitude affect soil erodibility and the multifractal dimensions of PSD during natural recovery. We collected soil samples from grassland, shrubland, and forests with different restoration ages in the steppe zone (SZ), forest-steppe zone (FSZ), and forest zone (FZ). Various analyses were conducted on the samples, including multifractal analysis and erodibility analysis. Our results showed that restoration age had no significant effect on the multifractal dimensions of PSD (capacity dimension (D0), information dimension (D1), information dimension/capacity dimension ratio (D1/D0), correlation dimension (D2)), and soil erodibility. Multifractal dimensions tended to increase, while soil erodibility tended to decrease, with restoration age. Latitude was negatively correlated with fractal dimensions (D0, D2) and positively correlated with K and D1/D0. During vegetation restoration, restoration age, precipitation, and temperature affect the development of vegetation, resulting in differences in soil organic carbon, total nitrogen, soil texture, and soil enzyme activity, and by affecting soil structure to change the soil stability. This study revealed the impact of restoration age and latitude on soil erosion in the Loess Plateau.

Estimating the Soil Hydraulic Functions of Some Olive Orchards: Soil Management Implications for Water Saving in Soils of Salento Peninsula (Southern Italy)

Saving water resources in agriculture is a topic of current research in Mediterranean environments, and rational soil management can allow such purposes. The Beerkan Estimation of Soil Transfer parameters (BEST) procedure was applied in five olive orchards of Salento peninsula (southern Italy) to estimate the soil physical and hydraulic properties under alternative soil management (i.e., no-tillage (NT) and minimum tillage (MT)), and to quantify the impact of soil management on soil water conservation. Results highlighted the soundness of BEST predictions since they provided consistent results in terms of soil functions or capacitive-based soil indicators when (i) the entire data set was grouped by homogeneous classes of texture, bulk density, and capillarity of the soil, (ii) the predictions were compared with the corresponding water retention measures independently obtained in lab, and (iii) some correlations of literature were checked. BEST was applied to establish a comparison at Neviano (NE) and Sternatia (ST) sites. The two neighboring NT soils compared at NE showed substantial discrepancies in soil texture (i.e., sandy loam (NE-SL) or clay (NE-C)). This marked difference in soil texture could determine a worsening of the relative field capacity at the NE-SL site (relative field capacity, RFC &lt; 0.6), as compared to NE-C where RFC was optimal. The current soil management determined a similar effect (RFC &lt; 0.6) at Sternatia (ST-MT vs. ST-NT), but the worsening in soil properties, due to soil tillage, must be considered substantially transient, as progressive improvement is expected with the restoration of the soil structure. The results of this work suggest that strategic MT can be a viable solution to manage the soil of Salento olive orchards.

Modeling the hydrophysical soil properties and comparative analysis for three systems of functions

A functional description of the hydrophysical properties of the soil as a capillary-porous medium is presented. The described functions of water retention capacity and hydraulic conductivity of the soil have common parameters, which are interpreted within the framework of physical and statistical concepts. The practical significance of the proposed functions lies in the fact that the volume of labor-intensive field measurements necessary, for example, for modeling the dynamics of soil moisture, is significantly reduced. To identify the parameters of these functions, it is sufficient to use data only on the water retention capacity of the soil. The parameters identified in this way can be used to predict the ratio of the hydraulic conductivity of the soil to the moisture filtration coefficient. The presented system of the hydrophysical functions of the soil is compared with world analogues using literature data on soils of different texture.

Soil water and fuel permeability of a Cambisol in southern Brazil and its spatial behavior: A case study

AbstractThe high demand for fuel derived from oil increases the risk of environmental hazard in agricultural fields caused by accidents with the operation of machines and spotting of fuel on the ground. When these accidents occur, a part of the spilled fuel infiltrates and redistributes in the soil according to the fuel's own physical properties. Most fuel products are light nonaqueous‐phase liquids (NAPL) and contain compounds that are toxic and cause damage to the soil and to human health. The transport behavior of fuels in soils has been extensively studied but is lacking knowledge in specific soils with high clay content. This study aimed to evaluate the soil permeability (K) to the transport of water and fuels and their spatial variation in a Cambisol in southern Brazil. Furthermore, the question should be addressed whether Kwater may be used to estimate Kfuels based on the fluid viscosities. Moreover, a spatial variance analysis should evaluate the variability between replicate repacked samples at a particular location in comparison with spatial variability caused by soil texture and bulk density differences. Results showed that Kwater was, on average, 4.5 times smaller than Kgasoline and 1.25 times smaller than Kdiesel, that the correlation between measured and estimated Kfuels was moderately positive for the clayey soil investigated, and that a minimum set of three repacked parallel cores for each sampling location yields a local variance that is much smaller than the semivariance at any lag distance.

Composition of organic C fractions in soils of different texture affected by sugarcane monoculture

ABSTRACT Sugarcane is a strategic commodity in Indonesia. It is usually raised in a monoculture system. There is a lack of information about the effects of extended sugarcane monoculture on the soil carbon fraction. The aim of this study was to determine the relative changes in the soil organic C fractions in response to the duration of sugarcane monoculture on Entisols, Inceptisols, and Vertisols. The measured variables were the percentages of sand, silt, and clay, organic matter (OM), total nitrogen (TN), pH (H2O), cation exchange capacity (CEC), NH4 +, NO3 -, labile carbon fraction (soil carbon mineralization (C-Min), soil microbial carbon (C-Mic), and carbon particulate organic matter (C-POM)), and stable carbon fraction (humic and fulvic acids). Soil type with sugarcane monoculture period had significant influences on the percentages of clay, sand, silt, CEC, and pH (H2O). Soil type and sugarcane monoculture period had no apparent significant effect on C-Min or C-POM but did significantly influence C-Mic. The humic and fulvic acid levels in all three soil types were affected by the duration of sugarcane monoculture. To establish the impact of long-term sugarcane monoculture on the physicochemical properties of soils with various textures, it is more appropriate to measure the soil stable carbon fractions such as humic and fulvic acid rather than the soil labile carbon fractions such as C-Min, C-POM, or C-Mic.

Calibration method affects the measured δ2H and δ18O in soil water by direct H2Oliquid–H2Ovapour equilibration with laser spectroscopy

AbstractThe direct H2Oliquid–H2Ovapour equilibration method utilizing laser spectroscopy (DVE‐LS) is a way to measure soil pore water stable isotopes. Various equilibration times and calibration methods have been used in DVE‐LS. Yet little is known about their effects on the accuracy of the obtained isotope values. The objective of this study was to evaluate how equilibration time and calibration methods affect the accuracy of DVE‐LS. We did both spiking and field soil experiments. For the spiking experiment, we applied DVE‐LS to four soils of different textures, each of which was subjected to five water contents and six equilibration times. For the field soil experiment, we applied three calibration methods for DVE‐LS to two field soil profiles, and the results were compared with cryogenic vacuum distillation (CVD)‐LS. Results showed that DVE‐LS demonstrated higher δ2H and δ18O as equilibration time increased, but 12 to 24 hr could be used as optimal equilibration time. For field soil samples, DVE‐LS with liquid waters as standards led to significantly higher δ2H and δ18O than CVD‐LS, with root mean square error (RMSE) of 8.06‰ for δ2H and 0.98‰ for δ18O. Calibration with soil texture reduced RMSE to 3.53‰ and 0.72‰ for δ2H and δ18O, respectively. Further, calibration with both soil texture and water content decreased RMSE to 3.10‰ for δ2H and 0.73‰ for δ18O. Our findings conclude that the calibration method applied may affect the measured soil water isotope values from DVE‐LS.

Estimating soil bulk density with combined commercial soil water content and thermal property sensors

Accurate information of soil bulk density (ρb) is essential for many models that predict soil water, gas, and heat transfer processes and for estimating soil carbon pools. Several indirect methods have been used to estimate ρb as a derivative of various soil properties. One approach is to estimate ρb from soil thermal conductivity (λ) and volumetric water content (θw) measured with a custom fabricated sensor (thermo-TDR). In this study, we introduce a new approach to determine ρb with a combination of commercially available θw and thermal property sensors. Repacked samples of four differently-textured soils and a field experiment on a clay soil were used to evaluate the ability of four available sensors from METER Group, Inc. (Pullman, WA, USA) to estimate ρb. The θw was measured with the GS3 and EC-5 sensors, and soil λ was determined with the TR-1 and SH-1 thermal property sensors. The θw and λ measurements were used to determine ρb inversely from a λ-model. Compared with the GS3 sensor, the EC-5 sensor provided more accurate measurements of θw for the investigated soils, and thus, the EC-5 sensor was used with the new ρb estimation approach. Both TR-1 and SH-1 sensors gave accurate λ estimates when compared to modeled values. The ρb estimates with the TR-1/EC-5 and SH-1/EC-5 sensor combination methods agreed well with independent gravimetrically-derived ρb values of the repacked samples and the in-situ measurements, with average root mean square errors of 0.12 and 0.13 Mg m−3, respectively. Thus, the commercial multi-sensor combinations can provide accurate ρb estimates similar to those with custom fabricated thermo-TDR sensors, and they are simpler to operate than the custom fabricated sensors.