نتایج جستجو برای: soil water

تعداد نتایج: 692592  

2008
Joel B. Sankey Rick L. Lawrence Jon M. Wraith

Agricultural producers require knowledge of soil water at plant rooting depths,while many remote sensing studies have focused on surface soil water or mechanisticmodels that are not easily parameterized. We developed site-specific empirical models topredict spring soil water content for two Montana ranches. Calibration data sample sizeswere based on the estimated variability of soil water and t...

1999
Thomas Harter Dongxiao Zhang

Although the spatial variability of water content is expected to be significant in heterogeneous, unsaturated media, its effect on solute transport has been neglected in most stochastic analyses. In this work we develop, evaluate, and numerically verify an analytical model describing the statistical moments of water content, soil water flux, soil water velocity, and solute spreading in the unsa...

2016
Jesús M Marín-Benito María J Sánchez-Martín M Sonia Rodríguez-Cruz

Intensive crop production involves a high consumption of pesticides. This is a cause of major environmental concern because the presence of pesticides in water is becoming increasingly common. Physicochemical methods based on soil modification with organic residues have been developed to enhance the immobilization and/or degradation of pesticides in agricultural soils, which may control both th...

Journal: :iran agricultural research 2007
m. parsinejad y. feng b. ghanbarian

soil water content is one of the most important parameters for estimating irrigation frequency and providing the plant’s water requirement. since measurement of soil water content is both expensive and time consuming, water movement models are used to estimate these values. in this study, leachw model was used to estimate soil water content for two “dry” (20-29 aug) and “wet” (1-6 jul) periods ...

Journal: :Tree physiology 1996
P. J. Dye

The use of potential transpiration models to simulate transpiration rates in areas prone to soil water deficits leads to overestimates of water use as the soil dries. Therefore, I carried out studies on Eucalyptus grandis W. Hill ex Maiden trees subjected to soil drying at two field sites in the Mpumalanga province of South Africa to determine the relation between transpiration rate and soil wa...

2014
Keith R. Daly Sacha J. Mooney Malcolm J. Bennett Neil M. J. Crout Saoirse R. Tracy

Short title for page headings: Influence of the rhizosphere on soil hydraulic properties 16 17 Short statement: Using non-destructive imaging techniques and numerical modelling we 18 quantify differences in hydraulic and structural properties of bulk and rhizosphere soil for 19 sand and clay loam soils. 20 21 22 2 1. Abstract 23 Understanding the dynamics of water distribution in soil is crucia...

Journal: :Journal of environmental quality 2013
Helena Andersson Lars Bergström Faruk Djodjic Barbro Ulén Holger Kirchmann

Eutrophication, a major problem in many fresh and brackish waters, is largely caused by nonpoint-source pollution by P from agricultural soils. This lysimeter study examined the influence of P content, physical properties, and sorption characteristics in topsoil and subsoil on P leaching measured during 21 mo in 1-m-long, undisturbed soil columns of two clay and two sandy soils. Total P losses ...

2014
J. HEPPELL

Management and irrigation of plants increasingly relies on accurate mathematical models for the movement of water within unsaturated soils. Current models often use values for water content and soil parameters that are averaged over the soil profile. However, many applications require models to more accurately represent the soil–plant–atmosphere continuum, in particular, water movement and satu...

Journal: :Journal of environmental quality 2007
Suduan Gao Thomas J Trout

Reducing emissions is essential for minimizing the impact of soil fumigation on the environment. Water application to the soil surface (or water seal) has been demonstrated to reduce 1,3-dichloropropene (1,3-D) emissions in soil column tests. This study determined the effectiveness of water application to reduce emissions of 1,3-D and chloropicrin (CP) in comparison to other surface seals under...

2009
ChengYi ZHAO Yu SHENG

Wheat growth in response to soil water deficit play an important role in yield stability. A field experiment was conducted for winter wheat (Triticum aestivum L.) during the period of 2002–2005 to evaluate the effects of limited irrigation on winter wheat growth. 80%, 70%, 60%, 50% and 40% of field capacity was applied at different stages of crop growth. Photosynthetic characteristics of winter...

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