SILICA IN SOIL SOLUTIONS: I. THE FORM AND CONCENTRATION OF DISSOLVED SILICA IN AQUEOUS EXTRACTS OF SOME SOILS

1963 ◽  
Vol 43 (1) ◽  
pp. 70-82 ◽  
Author(s):  
J. A. McKeague ◽  
M. G. Cline
Keyword(s):  
Soil Water ◽  
Silica Sol ◽  
Dissolved Silica ◽  
Water Extracts ◽  
Soil Solutions ◽  
Silica Concentration ◽  
Soluble Silica ◽  
Water Ratio ◽  
Different Soils

The effects of method of equilibration, soil-water ratio, pH, and temperature on the form and concentration of dissolved silica in soil-water mixtures were studied and some hypotheses concerning the role of soluble silica in soil development were evaluated in the light of the information obtained.Studies of methods of equilibrating soil-water mixtures showed that, with medium- and coarse-textured soils, shaking for a month resulted in increasing concentrations of dissolved silica with time. Concentrations of dissolved silica in similar mixtures that were allowed to stand were much lower and they changed very slowly with time after a few days. Shaking techniques are not suitable for obtaining equilibrium water-extracts of some soils.Concentrations of dissolved silica in water extracts of the soils studied increased with temperature and with soil-solution ratio, and decreased with increasing pH. The dissolved silica concentration of extracts of different soils ranged from less than 1 to more than 20 p.p.m. Monomeric silica, presumably Si(OH)4, was the form of dissolved silica in all of the extracts studied. This result discounts hypotheses of soil genesis involving silica sol.

Alkaline activation of metakaolinite-silica mixtures: Role of dissolved silica concentration on the formation of geopolymers

2017 ◽  
Vol 43 (15) ◽  
pp. 12641-12650 ◽  
Author(s):  
Maroua Glid ◽  
Isabel Sobrados ◽  
Hafsia Ben Rhaiem ◽  
Jesús Sanz ◽  
Abdeslem Ben Haj Amara
Keyword(s):  
Dissolved Silica ◽  
Alkaline Activation ◽  
Silica Concentration

Time and Moisture Effects on Total and Bioavailable Copper in Soil Water Extracts

2004 ◽  
Vol 33 (2) ◽  
pp. 505 ◽  
Author(s):  
Andreas Tom-Petersen ◽  
Hans Christian Bruun Hansen ◽  
Ole Nybroe
Keyword(s):  
Soil Water ◽  
Water Extracts ◽  
Moisture Effects

Excitation-Emission-Matrix Fluorescence Spectroscopy of Soil Water Extracts to Predict Nitrogen Mineralization Rates

2018 ◽  
Vol 82 (1) ◽  
pp. 126-135 ◽  
Author(s):  
Oshri Rinot ◽  
William R. Osterholz ◽  
Michael J. Castellano ◽  
Raphael Linker ◽  
Matt Liebman ◽  
...  
Keyword(s):  
Fluorescence Spectroscopy ◽  
Soil Water ◽  
Nitrogen Mineralization ◽  
Water Extracts ◽  
Excitation Emission Matrix

scholarly journals A thermodynamic formulation of root water uptake

2016 ◽  
Vol 20 (8) ◽  
pp. 3441-3454 ◽  
Author(s):  
Anke Hildebrandt ◽  
Axel Kleidon ◽  
Marcel Bechmann
Keyword(s):  
Soil Water ◽  
Water Uptake ◽  
Water Distribution ◽  
Bound Water ◽  
Root Water Uptake ◽  
Flow Path ◽  
Thermodynamic Evaluation ◽  
Entire Flow ◽  
Soil Water Distribution

Abstract. By extracting bound water from the soil and lifting it to the canopy, root systems of vegetation perform work. Here we describe how root water uptake can be evaluated thermodynamically and demonstrate that this evaluation provides additional insights into the factors that impede root water uptake. We derive an expression that relates the energy export at the base of the root system to a sum of terms that reflect all fluxes and storage changes along the flow path in thermodynamic terms. We illustrate this thermodynamic formulation using an idealized setup of scenarios with a simple model. In these scenarios, we demonstrate why heterogeneity in soil water distribution and rooting properties affect the impediment of water flow even though the mean soil water content and rooting properties are the same across the scenarios. The effects of heterogeneity can clearly be identified in the thermodynamics of the system in terms of differences in dissipative losses and hydraulic energy, resulting in an earlier start of water limitation in the drying cycle. We conclude that this thermodynamic evaluation of root water uptake conveniently provides insights into the impediments of different processes along the entire flow path, which goes beyond resistances and also accounts for the role of heterogeneity in soil water distribution.

The role of tree stem proximity in the spatial variability of soil water repellency in a eucalypt plantation in coastal Portugal

Soil Research ◽  
2005 ◽  
Vol 43 (3) ◽  
pp. 251 ◽  
Author(s):  
J. J. Keizer ◽  
A. J. D. Ferreira ◽  
C. O. A. Coelho ◽  
S. H. Doerr ◽  
M. C. Malvar ◽  
...  
Keyword(s):  
Soil Water ◽  
Water Repellency ◽  
Soil Water Repellency ◽  
Individual Measurement ◽  
Hydrophobic Compounds ◽  
Ethanol Droplet ◽  
Central Portugal ◽  
Living Organisms ◽  
Tree Stem

Certain organic compounds derived from living organisms or their decaying parts are generally accepted to induce soil water repellency. Water repellency may therefore be expected to increase with proximity to organisms releasing hydrophobic compounds. This hypothesis is tested here for Eucalyptus globulus trees, since eucalypt species are frequently associated with elevated repellency levels. In a young, first-rotation plantation on coastal dune sands in central Portugal, repeat measurements of water repellency using the ‘Molarity of an Ethanol Droplet’ (MED) test were carried out in situ between April 2001 and May 2002. On 25 dates, repellency was measured at initially 2 and later 3 distances on 2 sides of 8–11 randomly selected trees. On 15 occasions, additional repellency measurements were performed within small grids aside 3 of the selected trees. The postulated decrease in topsoil water repellency with increased distance from eucalypt tree stems was found to apply on several individual measurement dates, as well as, more unexpectedly since repellency usually is a transient phenomenon, for the study period as a whole. The results confirm the general association of eucalypt trees with water repellency, and indicate that tree stem proximity is an important but not sufficient factor to explain repellency distribution in topsoil.

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