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Soil water content temporal-spatial variability of the surface layer of a Loess Plateau hillside in China; Variabilidade temporal e espacial da umidade do solo na camada superficial de uma encosta do Loess Plateau na China

HU, Wei; SHAO, Ming An; WANG, Quan Jiu; REICHARDT, Klaus
Fonte: São Paulo - Escola Superior de Agricultura Luiz de Queiroz Publicador: São Paulo - Escola Superior de Agricultura Luiz de Queiroz
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
66.39%
Surface soil moisture exhibits an important variability in terms of spatial and temporal domains, which may result in critical uncertainties for agricultural water management. The purposes of this study were (i) to characterize the temporal dynamics and stability of the spatial variability of the surface 0-6 cm soil water content θon a hill-slope; (ii) to investigate issues related to soil moisture conditions including dominating factors on soil moisture and to the estimation of the mean θ. During a period of more than one month θwas measured on thirteen days by Frequency Domain Reflectometry using a 10 x 10 m grid of measurement points covering a 60 x 280 m domain within a hill-slope of the Loess Plateau in China. Soil water content exhibited a moderate variability for each measurement date, and the correlation length (l) for θranged from 8.4 to 27.7 m. With the soil becoming drier, l decreased, the CV% and the sampling number for accurate mean θestimation increased. Aspect, elevation, organic matter content, clay content, and bulk density were the main influencing factors, whose extent of influence weakened with decreasing θ. Based on time stability analysis and on the correlation of mean relative difference of θwith the relative difference of dominating factors...

Impacts of land-use pattern on soil water-content variability on the Loess Plateau of China

SHE, D. L.; SHAO, M. A.; TIMM, L. C.; SENTIS, I. Pla; REICHARDT, K.; YU, S. E.
Fonte: TAYLOR & FRANCIS AS Publicador: TAYLOR & FRANCIS AS
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
66.41%
Long-term vegetation restoration carried out on the slopes of the Loess Plateau of China employed different spatial and temporal land-use patterns but very little is known about the effects of these patterns on soil water-content variability. For this study the small Donggou catchment was selected to investigate soil water-content distributions for three spatial scales, including the entire catchment area, sampling transects, and land-use systems. Gravimetric soil water contents were determined incrementally to a soil depth of 1.20 m, on 10 occasions from April to October, 2007, at approximately 20-day intervals. Results indicated that soil water contents were affected by the six land-use types, resulting in four distinct patterns of vertical distribution of soil moisture (uniform, increasing, decreasing, and fluctuating with soil depth). The soil water content and its variation were also influenced in a complex manner by five land-use patterns distributed along transects following the gradients of five similar slopes. These patterns with contrasting hydrological responses in different components, such as forage land (alfalfa)-cropland-shrubland or shrubland-grassland (bunge needlegrass)-cropland-grassland, showed the highest soil water-content variability. Soil water at the catchment scale exhibited a moderate variability for each measurement date...

Spatio-temporal variability behavior of land surface soil water content in shrub- and grass-land

HU, Wei; SHAO, Mingan; HAN, Fengpeng; REICHARDT, Klaus
Fonte: ELSEVIER SCIENCE BV Publicador: ELSEVIER SCIENCE BV
Tipo: Artigo de Revista Científica
Português
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66.35%
The knowledge of the relationship between spatial variability of the surface soil water content (theta) and its mean across a spatial domain (theta(m)) is crucial for hydrological modeling and understanding soil water dynamics at different scales. With the aim to compare the soil moisture dynamics and variability between the two land uses and to explore the relationship between the spatial variability of theta and theta(m), this study analyzed sets of surface theta measurements performed with an impedance soil moisture probe, collected 136 times during a period of one year in two transects covering different land uses, i.e., korshinsk peashrub transect (KPT) and bunge needlegrass transect (BNT), in a watershed of the Loess Plateau, China. Results showed that the temporal pattern of theta behaved similarly for the two land uses, with both relative wetter soils during wet period and relative drier soils during dry period recognized in BNT. Soil moisture tended to be temporally stable among different dates, and more stable patterns could be observed for dates with more similar soil water conditions. The magnitude of the spatial variation of theta in KPT was greater than that in ENT. For both land uses, the standard deviation (SD) of theta in general increased as theta(m) increased...

Análise da influência do teor de umidade na absorção d'água e sucção dos solos em estudo de erodibilidade; Analysis of the influence of moisture content on water absorption and suction in soil studies erodibility

Menezes, Marla Bruna Melo de
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 05/04/2010 Português
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66.35%
O estudo da erodibilidade ganha importância quando se tratam de solos localizados em regiões tropicais, caracterizadas por altas pluviosidades e evaporações que dificilmente permitem ao maciço atingir um estado de saturação em campo. A erodibilidade e as propriedades hidráulicas determinam as condições de infiltração e de escoamento superficial e podem acelerar as feições erosivas através das perdas de partículas. Neste trabalho, observou-se que o grau de saturação in situ estabelece um potencial de sucção matricial (Sm) capaz de orientar o fluxo, absorção e armazenamento da água nos poros do solo. Deste modo, foi possível correlacionar as propriedades de absorção de água com as sucções mátricas de três solos (arenoso, argiloso e areno-argiloso), com comportamento erosivo e não-erosivo, ensaiados a diferentes teores de umidade inicial. Após o controle da sucção e umidade, através da panela de pressão de Richards, os solos foram submetidos ao ensaio de erodibilidade proposto por Nogami & Villibor (1979). Os índices de absorção (Iabs), de perda de massa por imersão (P) e de erodibilidade (E) determinados neste ensaio, quando correlacionados com as curvas características dos solos, mostraram a influência da sucção matricial no início do processo erosivo. Verificou-se uma tendência de aumento da perda de massa por imersão...

Soil-geosynthetic inclined plane shear behaviour: influence of soil moisture content and geosynthetic type

Maria-Lurdes Lopes; Fernanda Ferreira; José Ricardo Carneiro; Castorina Silva Vieira
Fonte: Universidade do Porto Publicador: Universidade do Porto
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
66.46%
This paper deals with the inclined plane shear on three different geosynthetics (a geocomposite (GC), a non-woven geotextile (GTX), and an extruded geogrid (GGR)) with a residual soil from granite. Soil and geosynthetic properties, test equipment, and procedures are described. The influence of soil moisture content and geosynthetic type on soilgeosynthetic interaction behavior is discussed by analyzing the results of the inclined plane shear tests. The main conclusions that can be outlined from the present study are the following: (1) the influence of soil moisture content was relevant for the soilGTX and soilGC interfaces. Indeed, the resistance of those interfaces decreased with the increase of soil moisture content. No significant differences were observed between the behavior of those geosynthetics; (2) the influence of soil moisture content on the behavior of the soilGGR interface was less evident. A slight decrease on the interface friction angle was only observed for the highest soil moisture content; (3) the dry soilGGR interface resistance was lower than that observed for the other two geosynthetics due to the relevance of soilsoil friction at the GGR apertures, to the high percentage of fines of the soil used in the research (D50#8202;=#8202;1·00 mm)...

Fine-root dynamics, soil moisture and soil carbon content in a Eucalyptus globulus plantation under different irrigation and fertilization regimes

Fabião, António; Katterer, Thomas; Madeira, M.; Ribeiro, C.; Steen, E.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em //1995 Português
Relevância na Pesquisa
76.37%
The minirhizotron technique was used to study the temporal dynamics of fine-roots over a 10 month period in a Eucalyptus plantation in central Portugal.Four treatments were applied:a control without irrigation or fertilisation( C), fertilisation twice per year (F), irrigated without fertilisation( I), and irrigated and fertilised once each week with fertiliser in the irrigation water (IL). In I and IL a drip-tube system was used,and fertiliser rates were adjusted based on the estimated plant nutrient demand. Soil moisture content was measured during the same period at 5 cm depth intervals down to 90 cm depth.Soil carbon content was measured at planting,30 months after planting and54 months after planting.Interrelations between fine-root dynamics, soil moisture , and soil carbon content are discussed.

Geostatistical analysis for soil moisture content under the no tillage cropping system

Grego,Célia Regina; Vieira,Sidney Rosa; Antonio,Aline Maria; Della Rosa,Simone Cristina
Fonte: São Paulo - Escola Superior de Agricultura "Luiz de Queiroz" Publicador: São Paulo - Escola Superior de Agricultura "Luiz de Queiroz"
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/08/2006 Português
Relevância na Pesquisa
76.43%
Experiments in agriculture usually consider the topsoil properties to be uniform in space and, for this reason, often make inadequate use of the results. The objective of this study was to assess the variability for soil moisture content using geostatistical techniques. The experiment was carried out on a Rhodic Ferralsol (typic Haplorthox) in Campinas, SP, Brazil, in an area of 3.42 ha cultivated under the no tillage system, and the sampling was made in a grid of 102 points spaced 10 m x 20 m. Access tubes were inserted down to one meter at each evaluation point in order to measure soil moisture contents (cm³ cm-3) at depths of 30, 60 and 90 cm with a neutron moisture gauge. Samplings were made between the months of August and September of 2003 and in January 2004. The soil moisture content for each sampling date was analyzed using classical statistics in order to appropriately describe the central tendency and dispersion on the data and then using geostatistics to describe the spatial variability. The comparison between the spatial variability for different samplings was made examining scaled semivariograms. Water content was mapped using interpolated values with punctual kriging. The semivariograms showed that, at the 60 cm depth...

Soil water content temporal-spatial variability of the surface layer of a Loess Plateau hillside in China

Hu,Wei; Shao,Ming An; Wang,Quan Jiu; Reichardt,Klaus
Fonte: São Paulo - Escola Superior de Agricultura "Luiz de Queiroz" Publicador: São Paulo - Escola Superior de Agricultura "Luiz de Queiroz"
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2008 Português
Relevância na Pesquisa
66.39%
Surface soil moisture exhibits an important variability in terms of spatial and temporal domains, which may result in critical uncertainties for agricultural water management. The purposes of this study were (i) to characterize the temporal dynamics and stability of the spatial variability of the surface 0-6 cm soil water content θon a hill-slope; (ii) to investigate issues related to soil moisture conditions including dominating factors on soil moisture and to the estimation of the mean θ. During a period of more than one month θwas measured on thirteen days by Frequency Domain Reflectometry using a 10 x 10 m grid of measurement points covering a 60 x 280 m domain within a hill-slope of the Loess Plateau in China. Soil water content exhibited a moderate variability for each measurement date, and the correlation length (l) for θranged from 8.4 to 27.7 m. With the soil becoming drier, l decreased, the CV% and the sampling number for accurate mean θestimation increased. Aspect, elevation, organic matter content, clay content, and bulk density were the main influencing factors, whose extent of influence weakened with decreasing θ. Based on time stability analysis and on the correlation of mean relative difference of θwith the relative difference of dominating factors...

Phytochemical and physiological changes in Ashwagandha (Withania somnifera Dunal) under soil moisture stress

Shah,Sonal; Saravanan,Raju; Gajbhiye,Narendra Atmaram
Fonte: Brazilian Journal of Plant Physiology Publicador: Brazilian Journal of Plant Physiology
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2010 Português
Relevância na Pesquisa
66.36%
Ashwagandha, commonly known as the Indian Ginseng (Withania somnifera) is an ingredient in many herbal preparations used for healing various ailments. It is cultivated in semi-arid regions of India as rain-fed crop. The response of this crop (cv. JA-134) to progressive soil moisture deficit on growth, physiology and content of phytochemicals was studied. At the end of treatment period, soil water potential (Ψw) decreased to -10.93, -1.15 MPa at 30 cm depth, predawn leaf water potentials were reduced to -0.62 and -0.51 MPa in the severe and moderate stress. Leaf area was reduced by 27.4% and 34.4% in moderate and severe water stress treatment compared to control. Chlorophyll content was reduced by 60% in the severe water stress. Changes in the steroidal alkaloids and lactones that are the major medicinal active principles derived from root extracts of this plant species was also analyzed. A reduction of 52.6% in net photosynthesis was noticed under severe stress. At the end of the treatment period, moderate and severe stress treatments had 0.751 and 0.714 mg g-1 12-deoxywithastramonolide (12-DWS) content in the roots respectively. The content of 12-DWS and withanolide were at 77% and 93% of the control in the moderate and severe stress...

Moisture content effect in the relationship between apparent electrical conductivity and soil attributes

Costa,Marcelo Marques; Queiroz,Daniel Marçal de; Pinto,Francisco de Assis de Carvalho; Reis,Elton Fialho dos; Santos,Nerilson Terra
Fonte: Editora da Universidade Estadual de Maringá - EDUEM Publicador: Editora da Universidade Estadual de Maringá - EDUEM
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2014 Português
Relevância na Pesquisa
86.5%
To map the spatial variability of a field to define the variable rate application, an intensive sampling of the soil-plant system is necessary. The apparent soil electrical conductivity (ECa) has been used for soil mapping because it correlates well with soil attributes, allows for dense sampling and can be obtained at low cost. However, ECa is influenced by soil moisture content, and the variability of this attribute can reduce the reliability of the ECa maps to explain the physical and chemical soil attributes. The objective of this study was to identify conditions that maximize the correlations between the ECa and the soil attributes. The results show that the mean soil moisture content of soil sampled on different dates was correlated with the mean of the ECa. The ideal time for measuring ECa occurred when the mean moisture content of the soil was higher. In this condition, the coefficient of variation for the soil moisture content was lower, there was no correlation between ECa and soil moisture content, and ECa was more correlated with other soil attributes evaluated in this work.

Assessment of Evapotranspiration and Soil Moisture Content Across Different Scales of Observation

Verstraeten, Willem W.; Veroustraete, Frank; Feyen, Jan
Fonte: Molecular Diversity Preservation International (MDPI) Publicador: Molecular Diversity Preservation International (MDPI)
Tipo: Artigo de Revista Científica
Publicado em 09/01/2008 Português
Relevância na Pesquisa
66.36%
The proper assessment of evapotranspiration and soil moisture content are fundamental in food security research, land management, pollution detection, nutrient flows, (wild-) fire detection, (desert) locust, carbon balance as well as hydrological modelling; etc. This paper takes an extensive, though not exhaustive sample of international scientific literature to discuss different approaches to estimate land surface and ecosystem related evapotranspiration and soil moisture content. This review presents: (i)a summary of the generally accepted cohesion theory of plant water uptake and transport including a shortlist of meteorological and plant factors influencing plant transpiration;(ii)a summary on evapotranspiration assessment at different scales of observation (sap-flow, porometer, lysimeter, field and catchment water balance, Bowen ratio, scintillometer, eddy correlation, Penman-Monteith and related approaches);(iii)a summary on data assimilation schemes conceived to estimate evapotranspiration using optical and thermal remote sensing; and(iv)for soil moisture content, a summary on soil moisture retrieval techniques at different spatial and temporal scales is presented.

Estimation of Soil Moisture Content from the Spectral Reflectance of Bare Soils in the 0.4–2.5 μm Domain

Fabre, Sophie; Briottet, Xavier; Lesaignoux, Audrey
Fonte: MDPI Publicador: MDPI
Tipo: Artigo de Revista Científica
Publicado em 02/02/2015 Português
Relevância na Pesquisa
66.46%
This work aims to compare the performance of new methods to estimate the Soil Moisture Content (SMC) of bare soils from their spectral signatures in the reflective domain (0.4–2.5 μm) in comparison with widely used spectral indices like Normalized Soil Moisture Index (NSMI) and Water Index SOIL (WISOIL). Indeed, these reference spectral indices use wavelengths located in the water vapour absorption bands and their performance are thus very sensitive to the quality of the atmospheric compensation. To reduce these limitations, two new spectral indices are proposed which wavelengths are defined using the determination matrix tool by taking into account the atmospheric transmission: Normalized Index of Nswir domain for Smc estimatiOn from Linear correlation (NINSOL) and Normalized Index of Nswir domain for Smc estimatiOn from Non linear correlation (NINSON). These spectral indices are completed by two new methods based on the global shape of the soil spectral signatures. These methods are the Inverse Soil semi-Empirical Reflectance model (ISER), using the inversion of an existing empirical soil model simulating the soil spectral reflectance according to soil moisture content for a given soil class, and the convex envelope model, linking the area between the envelope and the spectral signature to the SMC. All these methods are compared using a reference database built with 32 soil samples and composed of 190 spectral signatures with five or six soil moisture contents. Half of the database is used for the calibration stage and the remaining to evaluate the performance of the SMC estimation methods. The results show that the four new methods lead to similar or better performance than the one obtained by the reference indices. The RMSE is ranging from 3.8% to 6.2% and the coefficient of determination R2 varies between 0.74 and 0.91 with the best performance obtained with the ISER model. In a second step...

Soil moisture and soil type influence the breeding behavior of the pest snail Cernuella virgata (da Costa)

Cavagnaro, V.; Keller, M.; Baker, G.
Fonte: Elsevier Science BV Publicador: Elsevier Science BV
Tipo: Artigo de Revista Científica
Publicado em //2006 Português
Relevância na Pesquisa
76.33%
The common white snail (Cernuella virgata) (da Costa) is an exotic pest of grain crops in southern Australia. In order to better control these snails and develop optimal management strategies, it is important to understand how their breeding behavior is influenced by soil moisture and soil type. Pairs of adult snails were placed into vials containing either a calcareous or a non-calcareous soil at five moisture levels along their soil moisture retention curves: no-water; permanent wilting-point; mid-point; field-capacity; and saturation. Survival analysis was used to estimate the tendency of C. virgata to lay an egg cluster. ANOVA showed that there was no two-way interaction between soil moisture and soil type, however, one-way ANOVA showed that the tendency of C. virgata to deposit the first egg cluster was greater in the non-calcareous soil and increased as soil moisture increased. There was a higher total number of egg clusters laid in the non-calcareous soil. The total number of egg clusters laid in the two soil types increased as soil moisture content increased. No eggs were laid in the no-water treatment. C. virgata breed more frequently in moist soils, and egg laying is greater in wet seasons. Therefore the risk of grain contamination in spring is predicted to be greater following a relatively wet autumn and spring.; V.L. Carne-Cavagnaro...

A Method for Estimating the Profile Soil Moisture Content from ERS Scatterometer and Soil Data.

WAGNER Wolfgang; LEMOINE Guido; ROTT Helmut
Fonte: Centro Comum de Pesquisa da Comissão Européia Publicador: Centro Comum de Pesquisa da Comissão Européia
Tipo: Articles in Journals Formato: Printed
Português
Relevância na Pesquisa
66.37%
The potential of the ERS Scatterometer for soil moisture monitoring over the Ukraine is investigated. The ERS Scatterometer is a C-b..d radar with a spatial resolutionof 50 km. An algorithm for estimating the surface soil moisture content is applied to six years of data. A qualitative comparison with meteorological observations and auxiliary information indicates a good quality of the remotely sensed surface wetness values. A simple method is developed to relate the surface estimates with the profile soil moisture content. This model requires as input the remote sensing data and soil data encompassing wilting level, field capacity, and porosity. The method was validated with an extensive data set of gravimetric soil mosture measurements in the 0-20 cm and 0-100 cm layers from the agrometeorological network in the Ukraine. It is found that the ERS Scatterometer data can be used to distinguish about five soil moisture levels with good confidence.; JRC.(SAI)-Space Application Institute

The role of antecedent soil water content in the runoff response of semiarid catchments: a simulation approach

Castillo Sánchez, Victor Manuel; Gomez-Plaza, A.; Martínez-Mena García, M. Dolores
Fonte: Elsevier Publicador: Elsevier
Tipo: Artículo Formato: 579917 bytes; image/jpeg
Português
Relevância na Pesquisa
66.45%
The soil water content is recognized as one of many runoff controlling factors in semiarid environments. A simple, physically based distributed model has been developed to study the role of antecedent soil water content in runoff generation in three small catchments in semiarid southeast Spain. The catchments were set up in two different zones: a burnt area with scarce vegetation and unburnt area with a denser plant cover. The infiltration process is determined by the Green–Ampt equation and the initial soil water content is taken into account by means of maps obtained by Conditional Gaussian simulation. The model was run 2700 times with different soil moisture scenarios and design storms. Stochastic sensitivity analysis was used to examine the role of antecedent soil water content in the runoff response. The results showed that the hydrological response after high intensity, low frequency storms is independent of the initial soil water content. On the other hand, the antecedent soil water content is an important factor controlling runoff during medium and low intensity storms, a type of rainstorm that is relatively frequent in semiarid areas. The sensitivity of the runoff response to soil moisture depended on the predominant runoff mechanisms. When infiltration excess overland flow is predominant...

Factors regulating spatial distribution of soil water content in a small semiarid catchment

Gómez-Plaza, A.; Martínez-Mena García, M. Dolores; Albaladejo Montoro, Juan; Castillo Sánchez, Victor Manuel
Fonte: Elsevier Publicador: Elsevier
Tipo: Artículo Formato: 579917 bytes; image/jpeg
Português
Relevância na Pesquisa
76.46%
The factors which control soil moisture patterns in a semiarid area are determined in two different locations: a burnt zone with little vegetation and an unburnt zone with a greater vegetal cover. In the burnt area, the factors affecting the spatial variability of the soil water content are those considered as local controls such as soil texture and slope. These factors are able to explain a significant part of the spatial distribution of soil moisture in this zone independently of the soil moisture state. In the unburnt area, the factors affecting soil moisture were those related with the presence or absence of vegetation in semiarid environments. The upslope contributing area, aspect, soil profile curvature and soil depth best explained the spatial variability of the soil moisture content in the vegetated zone. The actual influence of these factors showed marked seasonal variations due to changes in the physiological activity of the vegetal cover. These factors, which are in part responsible for the distribution of soil moisture, are not commonly integrated in traditional topographic wetness indices. The topographic index of Beven and Kirkby (Beven, K.J., Kirkby, M., 1979. Hydrological Sciences Bulletin 24, 43–69) is extended to account for the interstorm soil water losses. The new indices incorporating the hillslope aspect improve the prediction power of soil water content patterns in semiarid areas.; Financial support from Spanish CICYT (HID98-1056-CO2-01) and Dirección General de Conservación de la Naturaleza-MIMAM (Programa RESEL).; Peer reviewed

A study of soil moisture across the Delmarva Peninsula from 2005-2008

Ippolito, Ryan
Fonte: University of Delaware Publicador: University of Delaware
Tipo: Tese de Doutorado
Português
Relevância na Pesquisa
66.35%
DeLiberty, Tracey; The annual cycle and persistence of soil moisture is influenced by a multitude of factors including such variables as soil type, vegetation cover, weather patterns, and seasonal variability. Utilizing data derived the Delaware Environmental Observing System (DEOS), a network of ground stations located throughout most of the Delmarva Peninsula, as well as remotely sensed observations using the NASA MODIS and AMSR-E satellite sensors, the spatial and temporal variability of soil moisture across the Delmarva Peninsula is determined. The vegetation indices and land surface temperatures provided by the MODIS satellite sensor provide an indication of soil moisture conditions at the land surface, and the AMSR-E satellite sensor gives a quantitative measure of soil moisture conditions at the top 1cm of soil. The remotely sensed data, used in conjunction with the DEOS ground-level observations of daily rainfall, maximum daily volumetric water content (30cm depth), and average daily air temperature provide insight into the conditions responsible for fluctuations in soil moisture conditions. The average soil moisture conditions at each ground station site were compared to one another in terms of soil texture and estimated field capacity. In general...

Using a Complex-Impedance Measuring Instrument to Determine In Situ Soil Unit Weight and Moisture Content

Meehan, Christopher L.; Hertz, Jason S.
Fonte: ASTM International Publicador: ASTM International
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
66.46%
Author's final manuscript; In situ measurements of soil unit weight and moisture content play a critical role in conventional compaction quality assurance and quality control procedures. Recently, there have been a number of attempts to develop alternative electrically-based test devices that can be used to measure the in situ unit weight and/or moisture content of a compacted soil; these devices are intended to serve as alternatives to more traditional tests such as sand cone, rubber balloon, drive cylinder, or nuclear density gauge tests. The study described in this paper focuses on the use of a relatively new electrically-based in situ soil test device that uses measurements of soil complex impedance, soil capacitance, and soil resistance to infer in situ soil unit weight and moisture content; this device is typically referred to as a complex-impedance measuring instrument (CIMI). This paper provides a detailed explanation of current CIMI operating principles and also describes the utilization of a CIMI for field- and laboratory-based testing. The CIMI used in this study was calibrated and assessed in two field compaction projects in which different silty sands were used for construction. A mold-based calibration approach was developed for building an electrically-based soil model using the CIMI; this approach provides an alternative to field calibration of the device. In order to perform a more complete assessment of the CIMI in a controlled environment...

Soil water content temporal-spatial variability of the surface layer of a Loess Plateau hillside in China; Variabilidade temporal e espacial da umidade do solo na camada superficial de uma encosta do "Loess Plateau" na China

Hu, Wei; Shao, Ming An; Wang, Quan Jiu; Reichardt, Klaus
Fonte: Universidade de São Paulo. Escola Superior de Agricultura Luiz de Queiroz Publicador: Universidade de São Paulo. Escola Superior de Agricultura Luiz de Queiroz
Tipo: info:eu-repo/semantics/article; info:eu-repo/semantics/publishedVersion; ; ; ; ; Formato: application/pdf
Publicado em 01/01/2008 Português
Relevância na Pesquisa
66.39%
A umidade da camada superficial do solo apresenta uma variabilidade importante nos domínios espacial e temporal, que pode levar a incertezas críticas para o manejo agrícola da água. Os objetivos deste estudo incluíram: (i) a caracterização da dinâmica temporal e da estabilidade da variabilidade espacial da umidade θda camada 0-6 cm em uma encosta em declive; (ii) investigação de parâmetros ligados às condições de umidade, incluindo fatores dominantes da umidade na estimativa de um valor médio de q. Durante um período de mais de um mês, q foi medida em 13 dias com auxílio da técnica da Refletometria do Domínio da Frequência, em uma grade de 10 x 10 cm, cobrindo uma área de 60 x 280 m, situada em uma encosta do "Loess Plateau" da China. A umidade do solo apresentou variabilidade moderada em cada data de medida e o alcance da correlação (l) para q variou de 8,4 a 27,7 m. Com o solo mais seco, l decresceu, o CV% e o número de amostras necessário para obter uma média precisa, aumentaram. O aspecto, a elevação, o conteúdo de matéria orgânica e a densidade do solo foram os principais fatores interferentes na umidade, cuja intensidade de influência diminuiu com a umidade. Baseado na análise de estabilidade temporal e na correlação da diferença relativa média de θcom a diferença relativa média dos fatores dominantes...

Análise geoestatística do teor de água do solo sob sistema de cultivo em plantio direto; Geostatistical analysis for soil moisture content under the no tillage cropping system

Grego, Célia Regina; Vieira, Sidney Rosa; Antonio, Aline Maria; Della Rosa, Simone Cristina
Fonte: Universidade de São Paulo. Escola Superior de Agricultura Luiz de Queiroz Publicador: Universidade de São Paulo. Escola Superior de Agricultura Luiz de Queiroz
Tipo: info:eu-repo/semantics/article; info:eu-repo/semantics/publishedVersion; ; ; ; ; Formato: application/pdf
Publicado em 01/08/2006 Português
Relevância na Pesquisa
76.43%
Experiments in agriculture usually consider the topsoil properties to be uniform in space and, for this reason, often make inadequate use of the results. The objective of this study was to assess the variability for soil moisture content using geostatistical techniques. The experiment was carried out on a Rhodic Ferralsol (typic Haplorthox) in Campinas, SP, Brazil, in an area of 3.42 ha cultivated under the no tillage system, and the sampling was made in a grid of 102 points spaced 10 m x 20 m. Access tubes were inserted down to one meter at each evaluation point in order to measure soil moisture contents (cm³ cm-3) at depths of 30, 60 and 90 cm with a neutron moisture gauge. Samplings were made between the months of August and September of 2003 and in January 2004. The soil moisture content for each sampling date was analyzed using classical statistics in order to appropriately describe the central tendency and dispersion on the data and then using geostatistics to describe the spatial variability. The comparison between the spatial variability for different samplings was made examining scaled semivariograms. Water content was mapped using interpolated values with punctual kriging. The semivariograms showed that, at the 60 cm depth...