Spatial Variability Of Soil Characteristics Research Articles

Vis-NIR spectroscopy as an eco-friendly method for monitoring pedoenvironmental variations and pedological assessments in Lut Watershed, Central Iran

Soil spectroscopy has become an applicable method for monitoring and management of the spatial variability of soil characteristics. However, no widely knowledge about the potential application of this method in arid regions is still available. This research aimed to ascertain the performance of visible and near-infrared spectroscopy (Vis-NIR) to detect soil variations related to pedogenetic processes and pedoenvironmental conditions and to show the perspective of the most important variables changing spectral behavior in Lut Watershed. Twenty-three pedons in three clusters, including site 1 (xeric-mesic soil moisture-temperature regimes), site 2 (aridic-mesic, and aridic-thermic), and site 3 (extreme aridic-hyperthermic), with different geomorphology and lithology, were selected. Physicochemical properties and different iron forms were analyzed; X-ray diffraction (XRD), magnetic susceptibility (χlf), and Vis-NIR spectroscopy were also performed. The most important attributes influencing spectral morphology were related to soil texture, organic carbon content, clay mineralogy, evaporitic minerals (carbonate, halite, gypsum, and anhydrite), and iron oxides (goethite, hematite, and magnetite). Geometric parameters (area and depth) of absorption features located in 400–1000 nm (iron oxide), 2200 nm (clay), and 2340 nm (CaCO3) were significantly decreased by organic carbon in site 1. Increasing χlf values masked the wavelengths in 1400, 1540, 1750, and 1900 nm (CaSO4.2H2O) in site 2. Moreover, increasing salinity and anhydrite content covered the features of iron oxides in 400–570 nm in site 3. The finger-shaped absorption in 1450–1475 nm (CaSO4.2H2O) disappeared with an increasing amount of anhydrite and its degree of dehydration. Principal component analysis (PCA) showed a suitable performance for soil discrimination in the three climatic sites with different pedogenetic processes. Validation results by the partial least squares regression (PLSR) models indicated excellent accuracy in predicting CEC, EC, χlf, and gypsum content (RPIQ = 4.17, 3.00, 3.00, and 2.58, respectively) and good accuracy in predicting Fed and CCE (RPIQ = 2.30 and 2.06, respectively). Overall, spectral sensing was recognized as a suitable pedoenvironmental monitoring indicator for pedological assessments in Lut Watershed.

An integration of soil characteristics by using GIS based Geostatistics and multivariate statistics analysis Sultan Batheri block, Wayanad District, India

The study was to estimate the spatial variability of physico-chemical characteristics of soil by using GIS-based geostatistics and multivariate analysis in Sultan Batheri Block, Wayanad district. A combination of geostatistics and multivariate statistical analysis was used to scrutinise and compare the soil data for spatial assessment investigation. In total, 32 soil samples were collected during the summer season (March to May 2021), from different locations through random sampling. Analyzing the characteristics was determined using various standard analytical techniques. The multivariate statistical analysis investigated the excellent results of soil properties. The principal component analysis and correlation coefficient matrix analysis determined the interrelationships of soil properties and showed a good variance of SOC. The highest variation was observed in the SOC whereas the lowest variation was observed in Electrical Conductivity. In PCA analysis, we found that the KMO value is exactly following around 0.788 or slightly below, which is also not exactly optimal. However, since the value is higher than 0.5, soil data factor analysis might be helpful. There are two statistical analyses were used to depict the soil properties and exemplify the spatial variability of soil characteristics in a GIS environment. Inverse distance weighting and kriging were used to develop the spatial distribution of all soil characteristics. According to a prediction generated using ordinary kriging, the SOM shows a high level of spatial autocorrelation in a geostatistical analysis with an elevation range of 2261–2661 m. The R2 coefficient for all soil properties ranges from 0.0072 to 0.2862. The soil variable SOM and the elevation range of 2224 m have a significant spatial autocorrelation in the Kriging semivarigram model. The R2 coefficients for all soil properties ranged from 0.0072 to 0.3162. The interpolation method was relatively accurate for all soil parameters in both types. The cross-validation test results showed that the prediction of soil characteristics was of high accuracy. The levels of nitrogen and phosphorus in the study region are ideal. The study ensured that nitrogen, phosphorus, and other insecticides and herbicides were not used. The result reveals that there is no risk of contamination from nitrogen and phosphorus and that soil is unquestionably contamination-free.

Random Field Reliability Analysis for Time-Dependent Behaviour of Soft Soils Considering Spatial Variability of Elastic Visco-Plastic Parameters

• K-L expansion method was adopted to generate random field with different spatial correlation lengths • A critical spatial correlation length existed for predicting time-dependent settlement of soft soils • A single random variable analysis is not always the most conservative analysis in predicting settlement of soft soils • It is essential to perform random field analysis to reduce the risk of the design to be applied in construction. Low embankment strategy is one of the effective methods to control time-dependent settlement of soft soils in infrastructure construction projects. Spatial variability of soil characteristics is a crucial factor, affecting the reliability of predictions of the long-term settlement in soft soils. In this paper, the time-dependent behaviour of soft soils is analysed incorporating spatial variability of elastic visco-plastic model parameters. Standard Gaussian random fields for correlated elastic-plastic model parameter ( λ / V ) and the initial creep coefficient ( ψ 0 / V ) are generated adopting Karhunen-Loeve expansion method based on the spectral decomposition of correlation function into eigenvalues and eigenfunctions. Then the generated random fields are incorporated in the proposed non-linear elastic visco-plastic (EVP) creep model. The impacts of spatially variable elastic visco-plastic model parameters (i.e. ψ 0 / V and λ / V ) on long-term settlement predictions are evaluated through random field analysis (RF) with different spatial correlation lengths, and results are then compared to a single random variable (SRV) analysis. The probability of failure (PF) is calculated adopting RF and SRV analysis to determine the critical spatial correlation length, resulted in a maximum probability of failure. This study can be employed by design engineers to determine the critical spatial correlation length for safe design in the absence of adequate data to determine the exact spatial correlation length. The results also confirm that SRV analysis is not always the most conservative analysis in predicting time-dependent settlement of soft soils; and it is essential to perform RF analysis considering the spatial correlation length to reduce the risk and increase the reliability of the design to be applied in construction.

Characterizing spatial variability of some soil properties in Beni-Moussa irrigated perimeter from Tadla plain (Morocco) using geostatistics and kriging techniques

The research was carried out in Beni-Mousssa perimeter in the southern part of the Tadla plain, in Morocco. This study was performed using physicochemical analyses combined with statistical and geostatistical analysis to understand the spatial variability of soil quality in this agricultural area and to elaborate sustainable management of soil and environmental decision. The locations of sampling sites were defined by knowledge of the region’s farmers, on-site observations, and analyzed in the laboratory using the standard procedures for each soil property. A total of 67 soil samples were collected and analyzed in Geo-Resources and Environment Laboratories at the Faculty of Sciences and Techniques of Beni-Mellal, to identify physical and chemical soil properties especially pH, electrical conductivity (EC), organic carbon (OC), carbonate content (CaCO3), texture, exchangeable potassium (K), total phosphorus (P), total nitrogen (N), and cation exchange capacity (CEC). The soil presented an alkaline reaction. Other soil characteristics varied considerably in the overall study area. Pearson correlation among pH, soil OC, and CaCO3 were considered to be positive and significant (p < 0.05). Gaussian, exponential, spherical, and K-Bessel semivariogram models were selected, with weak to strong spatial dependency to be the better adjustment by using ordinary kriging techniques to estimate the spatial variability of soil characteristics. The obtained results revealed that the variation of soil characteristics in the study area depended on intrinsic and management soil factors. The detailed maps obtained in the framework of this type of study are very useful at international level in the selection of appropriate interventions, in particular with regard to the quantity of fertilizers, crop rotation, conservation and rehabilitation of deteriorated soils.

Integration of Soil Electrical Conductivity and Indices Obtained through Satellite Imagery for Differential Management of Pasture Fertilization

Dryland pastures in the Alentejo region, located in the south of Portugal, normally occupy soils that have low fertility but, simultaneously, important spatial variability. Rational application of fertilizers requires knowledge of spatial variability of soil characteristics and crop response, which reinforces the interest of technologies that facilitates the identification of homogeneous management zones (HMZ). In this work, a pasture field of about 25 ha, integrated in the Montado mixed ecosystem (agro-silvo-pastoral), was monitored. Surveys of apparent soil electrical conductivity (ECa) were carried out in November 2017 and October 2018 with a Veris 2000 XA contact sensor. A total of 24 sampling points (30 × 30 m) were established in tree-free zones to allow readings of normalized difference vegetation index (NDVI) and normalized difference water index (NDWI). Historical time series of these indices were obtained from satellite imagery (Sentinel-2) in winter and spring 2017 and 2018. Three zones with different potential productivity were defined based on the results obtained in terms of spatial variability and temporal stability of the measured parameters. These are the basis for the elaboration of differentiated prescription maps of fertilizers with variable application rate technology, taking into account the variability of soil characteristics and pasture development, contributing to the sustainability of this ecosystem.

Determination of homogeneous zones for liming recommendations of black pepper using geostatistics

ABSTRACT Studies aimed at determining homogeneous zones and the spatial variability of soil characteristics may improve the efficiency of agricultural input applications. The purpose of this study was to determine homogeneous zones for liming applications and to characterize the spatial variability of characteristics related to soil acidity and productivity in an Oxisol cultivated with black pepper (Piper nigrum L.). This study was carried out in São Mateus, state of Espírito Santo, Brazil. The experimental site was 100 x 120 m. A grid with 126 sampling points was established. Three soil sub-samples were collected at each sampling point in the black pepper canopy areas, at a 0-0.20 m depth. Crop productivity was estimated by harvesting the three plants neighboring each sampling point. Descriptive statistics and geostatistical analyses were performed. Homogeneous management zones were defined based on map of liming needs. Mathematical models adjusted to semivariograms indicated that all of the studied variables exhibited spatial dependency. An analysis of the spatial variability together with the definition of homogeneous zones can be used to increase the efficiency of soil liming.

Soil mapping for improved phenotyping of drought resistance in lowland rice fields

Phenotyping of drought resistance traits in rice is challenging at the field level due to the spatial variability of soil characteristics linked to soil water content. Apparent soil electrical conductivity (ECa) mapping may therefore be useful for characterizing spatial variability and improving phenotyping efforts in drought screening trials. ECa mapping was conducted over two seasons in lowland rice drought phenotyping trials. ECa was positively correlated with clay content and soil depth, and negatively correlated with volumetric soil water content during periods of moderate to severe drought. In addition, ECa was negatively correlated with indicators of plant performance including canopy temperature, normalized difference vegetation index, biomass, plant height, and grain yield. The results suggest that clay content and topsoil depth were the primary factors influencing the timing and severity of the drought response during the dry down of the field. Overall, the results illustrate the usefulness of ECa mapping for the spatio-temporal characterization of soil heterogeneity that influences plant performance under drought in lowland rice fields. ECa mapping can be useful for optimizing experimental plot layouts to ensure their uniformity and to improve validity of drought phenotyping and breeding trials.

Soil characteristics and herbicide sorption coefficients in 140 soil profiles of two irregular undulating to hummocky terrains of western Canada

Sensitive input parameters such as herbicide sorption coefficients are seldom quantified in sufficient spatial detail, leading to large uncertainties in pesticide fate model predictions at regional and national scales. This study examined the spatial variability of soil characteristics and herbicide sorption coefficients (Kd) in a total of 609 soil samples obtained from 140 soil profiles in two undulating to hummocky soil-landscapes of western Canada. In all soil horizons, Kd values were always the largest for glyphosate followed by atrazine then 2,4-D. In each soil-landscape, SOC, 2,4-D and atrazine Kd values (all strongly associated) numerically decreased with A>B>C mineral horizons, regardless of the segment of the slope in which the soil profile was located. SOC, 2,4-D Kd and atrazine Kd values were typically smaller in the eluvial A-horizons (Ae, Aej) than other A-horizons. In several landform elements, glyphosate Kd values were numerically greater in the B rather than the A or C mineral horizons. Glyphosate Kd values were particularly large in B-horizons with redoximorphic features such as in illuvial B-horizons enriched with clay (Btg, Btgj). When the soil properties and sorption values of similar horizons were compared across the soil-landscapes, SOC and 2,4-D Kd demonstrated greater coefficients of variation than atrazine Kd and glyphosate Kd. The strength of prediction equations for 2,4-D Kd and atrazine Kd were strong in each soil-landscape when all samples in the soil profile were included in the model. However, the strength of prediction equations by mineral horizon was generally weaker and in some cases not significant. The in-field variability of glyphosate Kd values could not be predicted from the measured soil properties data, or calculated digital terrain attributes. Terrain attributes also showed little to no correlation, or predictive strength for describing the variability of 2,4-D and atrazine sorption in the soil-landscapes.

Estimativa da infiltração de água no solo na escala de bacia hidrográfica

A variabilidade espacial das características do solo torna a estimativa da infiltração de água altamente dependente da escala de análise. Muitos trabalhos necessitam de informações da dinâmica da infiltração para descrever o mecanismo de outros processos associados à água, aos sedimentos ou aos solutos. O objetivo deste trabalho foi utilizar duas estratégias metodológicas para a estimativa da infiltração na escala de bacia. Os parâmetros de dois modelos de infiltração foram ajustados a um conjunto de dados coletados durante dois anos de monitoramento, em 77 eventos de chuva-vazão ocorridos sob diferentes condições de uso e manejo do solo numa bacia hidrográfica rural de 1,2 km². Os resultados dos ajustes para os dois modelos de infiltração na escala de bacia foram comparados com aqueles obtidos para dois métodos pontuais de estimativa da infiltração. Com o conjunto de dados do monitoramento, foi possível definir um modelo de infiltração para a bacia monitorada. Além disso, os resultados indicaram que a comparação realizada entre os valores dos modelos com os pontuais são fortemente dependentes da escala de análise; isto é, as medidas pontuais revelaram valores médios de taxa de infiltração alta para a bacia em estudo. Todavia, observações no campo indicaram baixa infiltração, principalmente nas áreas saturadas onde condicionam o escoamento superficial nessa bacia, ao contrário dos resultados pelos modelos de estimativa, que apresentaram menor ordem de magnitude dos valores estimados de infiltração, em razão, entre outros, da maior incorporação dos fatores controladores do processo em seu método.

Spatial variability of soil characteristics along a landscape gradient in Bellanwila-Attidiya area, Sri Lanka

Wetlands are comprised of unique components of soil, water and biodiversity which are interconnected. This ecosystem provides important ecological, social and economic services which are often unnoticed and undervalued. Although water and biodiversity components of wetlands are being somewhat investigated, a very few research have been carried out to investigate soil properties. This study focussed on spatial variability of soil chemical and physical parameters in a land use gradient around the Bellanwila-Attidiya Sanctuary, a wetland situated in Colombo suburbs. Main objective was to present a summary of spatial variation of soil characteristics and develop maps using GIS in different land use areas: natural-wetland; manmade-functioning paddy fields, non-functioning paddy fields, residential and industrial.This study was carried out for a period of 3 months and several random soil samples were obtained from all land use areas. The following parameters were analysed in triplicate, from the samples taken at the surface and at one m depth in the soil: chemical properties; NO3- , PO43-, SO42-, Cl- and Fe3+ and physical properties; moisture content, pH, salinity, electrical conductivity, temperature, soil type and soil colour. All analysis were carried out according to Standard Methods and the GIS maps were developed using ArcView GIS 3.2. The results indicated that all chemical and physical parameters of soil varied across the landuse gradient, except for temperature. According to the GIS maps there are apparent variations in distribution of soil properties. On the surface, the highest level of each parameter was found as follows: NO3- in industrial area, PO43- in functioning paddy fields, SO42- in residential area, Cl- in residential area, Fe3+ in functioning paddy fields, moisture content in wetland, pH in industrial area, salinity in residential area, electrical conductivity in residential area. At 1 m depth, the pattern was different: NO3- in abandoned paddy fields, PO43- in functioning paddy fields, SO42- in wetland, Cl- in wetland, Fe3+ in residential area, moisture content in wetland, pH in industrial area, salinity in wetland, electrical conductivity in wetland. The findings clearly exhibit the increases in anthropogenic pressure have resulted in wide-scale alternation of soil properties, at least in the surface soil, across a land use gradient. Managing land use in the watershed of the wetland thus needs adequate attention to conserve this natural ecosystem

Study on Spatial Variability of Soil Characteristics on Different Land Use Types Based on Land Parcel Scale - A Case Study in Kenli County

Soil characteristics spatial variability is one of the important attributes of soil, while land use is the most universal, the most direct and the most profound factor which affect soil quality. In this study, by the land statistics analysis of the soil characteristic in Kenli County, we study the spatial variability of soil characteristics on different land use types and the reasons for these variations produced. Research found that land use type has profound effect on soil characteristics in Kenli County. Different land parcel, different soil or terrain and different management measures can make it cause different variation structure.

CORRELAÇÃO ENTRE O CONTEÚDO DE ARGILA E A PROFUNDIDADE DE DEPOSIÇÃO DAS SEMENTES MILHO (Zea mays L.) EM PLANTIO DIRETO

The region of Campos Gerais, in the State of Paraná, is leader in grain yields and state-of-the-art no-tillage farming. The widely adopted no-tillage system tends to increment soil variability. There are several studies about spatial variability of soil characteristics affecting grain yield, but not enough attention has been given to the variability resulting of human actions. The objective of this study was to evaluate the correlation of soil clay content and the depth of placement of corn seeds on areas under no-till systems management. The four selected cornfields areas for the study are property of local farm cooperatives associates. The points for evaluation were defined consider-ing the local mapping of soil texture. Clay content varied from 94 to 489 g kg-1 on Plot 1; from 222 to 414 g kg-1 on Plot 2; from 269 to 509 of rows to be considered for plant distribution and seed depth analyses. The coefficient of variation (CV) of plant distribution was between 23 and 56%. For seed depth, the CV was between 18 and 34%. The regression analysis showed high coefficients of determination (r2) for plots 1 and 2 (r2=0,85 and 0,83). The clay content was generally higher on plots 3 and 4. In this case, the analysis of variance was not significant, and the coefficients of determination were low (r2=0,22 and 0,01). Results indicate that clay content values may be used to delimit g kg-1 on plot 3; and from 368 to 698 g kg-1 on plot 4. The type of planter determined the number management zones on the field, where the depth of seed placing in the planting process can be regulated in different ways.

Importance of agricultural chemistry in multifunctional crop production

agricultural production is a basic, traditional constituent of the Hungarian economy. An importance question nowadays is how the land can be cultivated and agricultural goods produced under the conditions of sustainable development. From the plant nutrition point of view the establishment of an environment-friendly fertilizer recommendation system is essential if sustainable development is to be achieved. Most experts agree that this type of fertilizer recommendation system is able to fulfil the growing demands of a growing population, while keeping the environment in good condition for the next generations. The experts also agree that fertilizer application could not be replaced widely with organic farming alone. An environmentally friendly fertilizer recommendation system has to be sensitive enough to respond to the effects of different conditions, e.g. great spatial variability of soil characteristics, mosaic-like soil cover, climate, crop rotation practices, soil nutrient supply, etc. There was a dramatic change in Hungarian agriculture at the beginning of the 90s, as the result of which the use of fertilizers decreased sharply for several reasons, e.g. privatization, changes in ownership, withdrawal of state subsidies for mineral fertilizers, drought, etc. Both Hungarian agriculture and the country as a whole is now facing two challenges, i.e. to overcome the economic difficulties and to complete the final phase of preparations to join the EU. Land use change scenarios have proved that the natural endowments of Hungary are suitable for integrating agricultural production with environmental and landscape protection and nature conservation.

Variabilidade espacial de características de solos na região do Planalto Médio, RS: II. análise da semivariância e da variância

A variabilidade espacial das características de solos da região do Planalto Médio (RS) foi estudada em seis glebas cultivadas com soja, por meio das análises da semivariância e da variância, em amostragem sistemática, para confirmar e detalhar resultados obtidos por análise da variância por amostragem aninhada; estimar a variância nas características dentro de unidades de mapeamento de solos e a extensão do uso de mapas de solos para avaliação de terras. O trabalho de campo foi realizado de dezembro de 1989 a março de 1990. Os resultados confirmam que características de solos dependentes de processos pedogenéticos mostram interdependência espacial de 500 m ou mais, porém a variância de características afetadas pelo manejo persistirá em espaçamentos menores. Outrossim, que qualidades da terra, como disponibilidade de nutrientes, não podem ser extraídas apenas de mapas de solos e que métodos alternativos de amostragem devem ser testados para amenizar o efeito negativo da variância de características a curtas distâncias na qualidade de mapas pedológicos.

Determination of infiltration rate from border irrigation advance and recession trajectories

A volume-balance technique utilizing irrigation advance and recession functions, numerical integration, and an optimization procedure was developed to determine infiltration parameters. The procedure is simple yet rational and accounts for spatial variability of soil characteristics. The required data are flow rate, the coefficients and exponents of the advance and recession functions, and inflow shut-off time. In a field experiment on a clay loam soil (typical of southern Alberta) at the Lethbridge Research Centre, infiltration rates estimated by this technique were similar and in close agreement with those measured with a ring infiltrometer. Except for two border strips, there were no significant mean differences between simulated ( I s) and measured ( I m) infiltration rates. In the two non-conforming border strips, field measured infiltration rates were higher than those simulated with the volume balance approach, most likely due mainly to spatial variability of soil characteristics and partly to lateral flow which occasionally occurs when measuring infiltration with a ring infiltrometer.

Surface water hydrology—runoff generation and basin structure

This review addresses the problem of developing a theory of the relationship between runoff generation and basin structure. It is suggested that the current generation of physically based models of basin hydrology cannot predict runoff generation in the field with any adequacy because they are not good descriptors of runoff processes, except under some special circumstances. Some of the complex factors contributing to runoff generation that lead to this conclusion are discussed. Special emphasis is placed on the problems posed by the spatial variability of soil characteristics to the application of physically based models. The way in which basin structure changes with spatial scale is then considered. The ordered nature of drainage basins suggests that it may be possible to develop some parsimonious theory relating basin structure to runoff generation. Finally, the importance of time scale is stressed. Changes in basin structure over time are frequently ignored in hydrological analysis. Over long periods of time these changes are on the average gradual, but over the time scale of years there may be important periods of change induced by extreme events. Such an event may affect runoff generation and the frequency characteristics of events that follow it, particularly in small basins. All these complicating factors affect our ability to predict the response of an ungauged basin using physically based models, one of the ultimate tests of physical hydrology.