Soil Science Society of America Journal, Nov 1, 2009
All rights reserved. No part of this periodical may be reproduced or transmitted in any form or b... more All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Permission for printing and for reprinting the material contained herein has been obtained by the publisher
ABSTRACT The assumption of zero trend seems unlikely for many soil properties that change systema... more ABSTRACT The assumption of zero trend seems unlikely for many soil properties that change systematically across the landscape. Removal of a trend may result in a bias in estimating the semivariogram and in many studies has not resulted in appar-ent improvements in kriging estimates. This study was conducted with the objective to use a proportional effect semivirogram model approach for handling a region with a pronounced trend aside from trend removal. To demonstrate this approach, soil samples (0–30-cm depth) were collected along four transects and analyzed for the electrical conductivity (EC) of the soil/water (1:5) extracts. The 50-m long transects centered on the points (x j) were from four subregions with maximum con-trast in salinity means [ m (x j)]. Fractile diagrams and goodness-of-fi t analysis at the 0.05 signi fi cance level indicated that the normal distribution function fi tted the EC values of the four transects. Except for transect T(x 1), a lognormal distribution func-tion might also be accepted. A proportional effect stationary semivariogram model: e / (,) () () j j s h x m x h ⎡ ⎤ Φ = ⎣ ⎦ γ γ was fi tted to the local experimental semivariograms g e (h , x j) by the steepest-descent optimization method. The predicted local dispersion variances were reasonable when compared with the experimental variances thereby supporting validity of the proposed model. Statistical analysis of cross validation (kriging) results con fi rmed the adequacy of the stationary semivariogram model and the validity of the estimated parameters. The assumption of quasi-stationary instead of stationary along the transect improved predictions of true kriging variance. The proportional effect quasi-stationary semivariogram models may offer a possible approach for krig handling a regionalized variable having a pronounced trend with-out the need for trend removal.
The adsorption of •87Cs by sediments from the Savannah River Plant follows a theoretically expect... more The adsorption of •87Cs by sediments from the Savannah River Plant follows a theoretically expected linear relationship between In Kd* and 1/T where Kd* and T are the equilibrium distribution coefficient (Cs adsorbed, meg g-VCs + in solution, meq ml-•) and the temperature in kelvins, respectively. The slope of these plots decreases after removal of hydroxy A1 interlayers with citrate pretreatment. Hydroxy AI interlayers thus make Cs + adsorption more temperature dependent. This thermal effect of hydroxy A1 interlayers becomes more significant in sediments containing a:nonswelling 2:1-2:2 intergrade clay mineral than in those containing a swelling 2:1-2:2 intergrade clay mineral. The phenomenon is explained by considering hydroxy A1 interlayers as a source of hydronium ions H80 + which compete with Cs + for exchange positions in wedge zones. An increase in temperature favors an increase in H,O + ions, which in turn favors less adsorption of Cs +. Aside from their thermal effect the positively charged hydroxy aluminum polymeric groups drastically decrease the cation exchange capacity and consequently the adsorption of cesium.
Zeitschrift für Pflanzenernährung und Bodenkunde, 1982
A compilation of some useful approaches used for the obtention of the minimum potential between i... more A compilation of some useful approaches used for the obtention of the minimum potential between interacting flat clay double layers is given. Values of the minimum potential obtained from published nomograms, tables and equations are compared. The effect of dissimilar double layers on the potential is also illustrated. Das elektrische Potential in der Mitte zwischen zwei sich uberlappenden Doppelschichten bei Tonmineralen: Eine Zusammenstellung der theoretischen Ansatze Es wird eine Zusammenstellung nutzlicher Verfahren zur Berechnung des Potentialminimums zwischen flachen, sich gegenseitig beeinflussenden Doppelschichten an Ton gegeben. Werte des Potentialminimums, die mit Hilfe von veroffentlichten Nomogrammen, Tabellen und Gleichungen gewonnen wurden, werden verglichen. Der Einflus von ungleichartigen Doppelschichten auf das Potential wird illustriert.
We demonstrate nearly-spherical, strain-free, self-assembled Ge quantum dots (QDs) fully encapsul... more We demonstrate nearly-spherical, strain-free, self-assembled Ge quantum dots (QDs) fully encapsulated by AlAs, grown on (100) GaAs by molecular beam epitaxy (MBE). The QDs were formed without a wetting layer using a high temperature, in-situ anneal. Subsequent AlAs overgrowth was free from threading dislocations and anti-phase domains. The straddling band alignment for Ge in AlAs promises strong and tunable confinement for both electrons and holes. The reflection high-energy electron diffraction (RHEED) pattern changed from 2×3 to 2×5 with anneal, which can be explained by surface reconstructions based on the electron-counting model.
Proceedings of 2nd International Conference on Recent Advances in Space Technologies, 2005. RAST 2005.
... Thanks to King Faisal University for partial fund. Thanks also extended to Dr. Masoud Abdel A... more ... Thanks to King Faisal University for partial fund. Thanks also extended to Dr. Masoud Abdel Atti, and Dr. Adel Hussain, of Water Studies Center, KFU for their technical assistance. ... [7] Elprince, AM, Turjoman, AM and Al-Dakheel , Y. (1983) Irrigation water requirements for soil ...
The adsorption of trace radioactive cesium by sediments from the Savannah River Plant area follow... more The adsorption of trace radioactive cesium by sediments from the Savannah River Plant area follows a theoretically expected linear relationship between In Kd* and the pH of the equilibrium solution, where Kd* is the equilibrium distribution coefficient: Cs adsorbed (meq g-•)/Cs + in solution (meq ml-•). Theoretically, the slope of these plots is proportional to the fraction of surface area occupied by pH dependent charges. Experimentally, the slope becomes zero after removal of hydroxy AI interlayers with citrate pretreatment. Hydroxy A1 interlayers are thus the main source for the pH dependent charges making Cs + adsorption pH dependent.
ABSTRACT Recording the decrease in weight with time upon heating by elec-trically reproducible in... more ABSTRACT Recording the decrease in weight with time upon heating by elec-trically reproducible infrared (IR) radiation offers a fast method for studying the kinetics of the dehydration of gypsiferous soils. Plotting the weight loss rate against time gives a dehydration curve made of two peaks. The first peak is due to soil moisture and the second to the crystal water of gypsum. The product of dehydration is best regarded as soluble anhydrite (CaSO 4 • e H,O) rather than henii-hydrate (CaSO 4 • iH 2 O) or insoluble anhydrite (CaSO 4). This is in-dicated by the loss in weight and the IR spectra. The kinetic curves for the dehydration of gypsum at 156, 123, and 95°C are of sigmoidal forms. Beyond the inflexion point, most of the data fits the "dimin-ishing sphere" kinetics formula. The rate constants and activation energies for the interface advance process shows that the soil matrix acts as a catalyst and that Na montmorillonite is a more effective catalyst than the soil matrix. A rate-limiting step for the interface advance is the necessity for crystal water to pass through an adsorbed state. Soil minerals may offer effective adsorption sites. In contrast to the growth process soil matrix is a more effective catalyst for nucleation than Na montmorillonite. Additional Index Words: thermodynamics of gypsum dehydration, crystal growth, nucleation.
ABSTRACT Data were obtained at 25°C on the composition of the aque-ous solution and exchanger pha... more ABSTRACT Data were obtained at 25°C on the composition of the aque-ous solution and exchanger phases in NH 4 -Ba-La, La-Ba, La-NH« and Ba-NH 4 aqueous systems comprising the chloride salts of the three cations and a montmorillonite clay from Neva-da. The data for the three binary cation exchange systems were incorporated into a thermodynamic model which was used to predict the composition of the aqueous solution phase of the ternary NH t -Ba-La system as a function of exchanger phase composition. The model employed, known as the sub-regular model, involved a MacLaurin expansion of the ex-changer phase rational activity coefficients to third order in the mole fractions of the exchanger components. The con-stant coefficients in the MacLaurin expansion could be deter-mined solely with experimental data on the infinite-dilution, rational activity coefficients of exchanger components hi binary exchange systems. Thus no data on ternary exchange sys-tems were required to apply the model. The model calcula-tions were in reasonably good agreement with experiment, suggesting that further efforts to predict ternary exchange be-havior from binary exchange data are warranted. Additional Index Words: exchanger phase activity coeffi-cients, thermodynamics of cation exchange.
Accurate prediction of the leaching requirements (Lr) of crops and striving to attain them is ess... more Accurate prediction of the leaching requirements (Lr) of crops and striving to attain them is essential for efficient irrigation water use. Solute modeling was extended to develop four Lr conceptual models that do not neglect solute reactions in the root-zone, surface evaporation, and the influence of immobile wetted pore space. The models were based on: (i) the water movement equation
Landsat TM5 still provide useful information about earth surface features although there are more... more Landsat TM5 still provide useful information about earth surface features although there are more advanced sensors with high capability of scanning and processing of remotely sensed data. In this respect, Landsat TM5 data were used to map saline soil and vegetation in one of the largest irrigated oases in the world. The study area is Al-Hassa oasis located in the southern part of the eastern region of Saudi Arabia. Main cultivated crops in the Al-Hassa area are date palm, alfalfa, vegetables, and some fruits. The most serious problem in the region is soil salinity that develop as a result of natural soil forming processes. The lack of the amount of irrigation water for cultivation raise the requirements to have proper management methods and adequate planning for the area. For the amelioration of salt affected soils and their effective utilization for successful plant production, it is necessary to establish rigorous management and frequent monitoring for these area. This research aimed to classify the vegetation in the scene image and to identify salt-affected soils in the study area. Two landsat TM5 images were used in this research. NDVI was calculated as a ratio between measured reflectivity in the red and near infrared bands. These two spectral bands are chosen because they are most affected by the absorption of chlorophyll in leafy green vegetation and by the density of green vegetation on the surface. Also, in red and near-infrared bands, the contrast between vegetation and soil is at a maximum. Therefore, NDVI relatively provided good results in classification of salt-affected and in distinguishing between vegetation classes.
A relatively rapid method based on using radioactive ions as tracers was developed for obtaining ... more A relatively rapid method based on using radioactive ions as tracers was developed for obtaining adsorption isotherms.' Cesium-Na adsorption isotherms were deter-mined for the < 100~-t fraction of two sediments before and after the removal of hydroxy Al interlayers with citrate. Removal of the interlayers from the sediment characterized with swelling 2:1-2:2 intergrade, while increasing the capacity to adsorb Cs, decreased Cs selectivity, the standard free energy change, and the density of surface charge. Such decreases were insignificant for the other sediment characterized with non-swelling 2:1-2:2 intergrade .
The adsorption of 137/sub Cs/ by sediments from the Savannah River Plant follows a theoretically ... more The adsorption of 137/sub Cs/ by sediments from the Savannah River Plant follows a theoretically expected linear relationship between ln Kd and l/T where kd and T are the equilibrium distribution coefficient and the temperature in kelvins, respectively. The slope of these plots decreases after removal of hydroxy Al interlayers. Hydroxy Al interlayers thus make Cs/sup +/ adsorption more temperature
ABsTRACT. Investigation of the origin of chemical composition of drainage water, accurate estimat... more ABsTRACT. Investigation of the origin of chemical composition of drainage water, accurate estimation of leaching requirement, and simulation of crop yield response are essentials for effective re-utilization of drainage water for irrigation and salinity control. The comprehensive chemical model SAO (for the chemical evolution of drainage waters and soil solutions) and the leaching requirement model LrSAO-e (for reactive salt), were verified using a new set of data. The new data are the results of water and soil analysis carried out in a pilot farm during leaching reclamation and by sampling an extension area in AI Hassa, Saudi Arabia. The steady-state SAO model was, originally, based on the changes in irrigation water composition, which occurred due to molecular-water loss, mineral precipitation and di ssolution, K+ fixa-tion, NaCI apparent retention, MgS04' formation, and biological formation of HCO) . Better model predictions were obtained by including CaS04' formation, an...
Soil sampling locations are, often, determined by visual estimations obtained from a base map. Oc... more Soil sampling locations are, often, determined by visual estimations obtained from a base map. Occasionally, one may need to use a map that contains little or no coordinate information. This is a problem if he intends to register this map with another in a multilayer database. In this paper we used the coordinates of selected ground control points (GCPs) obtained with a Trimble GPS unit to transform (register) the base map (1:10000 scale of unknown coordinate system) digitized in units of the base map into metric UTM system. Registration was done using affine transformation in ARCIINF GIS. The accuracy of this procedure was analyzed by comparing the GPS positions of one-way-roads with their corresponding GIS transformed positions. A 45-m buffer was required for at least 95% of the GIS roads to occupy the same GPS road positions. Thus, any resulted soil coverage map should be at a lower scale than the base map with a scale of 1: 45000 as an upper limit. Error budget analysis indicate...
Abstract The success of field fertilizer trials depends, largely, upon the selection of sites of ... more Abstract The success of field fertilizer trials depends, largely, upon the selection of sites of wide range in deficiencies for the nutrients under investigation. The date palm (Phoenix dactylifera L.,) cultures of AI Hassa region were grid-surveyed for appropriate sites to conduct field trials by P and K soil testing of 12,000 ha and 9,200 ha, respectively. The "NaHC0 3 (0.5 M) pH 8.5" and the "NH 4 AOc (1 M) pH 7" soil testing methods were used for P and K, respectively. Soil sampling involved the collection of two random composite soil samples (0-20 em depth) for each site. The 'T' composite was at a distance 1 m from the date palm stem and the 'U' composite represented the soil in between the date palms (inter-planted soils). The soil test values were grouped, based on approximate critical soil test levels, C (= 5 mg p/ kg soii for P and 60 mg K /kg soil for K) into five categories: probable response class (0 -2C), low residual class (2C -4C),...
Soil Science Society of America Journal, Nov 1, 2009
All rights reserved. No part of this periodical may be reproduced or transmitted in any form or b... more All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Permission for printing and for reprinting the material contained herein has been obtained by the publisher
ABSTRACT The assumption of zero trend seems unlikely for many soil properties that change systema... more ABSTRACT The assumption of zero trend seems unlikely for many soil properties that change systematically across the landscape. Removal of a trend may result in a bias in estimating the semivariogram and in many studies has not resulted in appar-ent improvements in kriging estimates. This study was conducted with the objective to use a proportional effect semivirogram model approach for handling a region with a pronounced trend aside from trend removal. To demonstrate this approach, soil samples (0–30-cm depth) were collected along four transects and analyzed for the electrical conductivity (EC) of the soil/water (1:5) extracts. The 50-m long transects centered on the points (x j) were from four subregions with maximum con-trast in salinity means [ m (x j)]. Fractile diagrams and goodness-of-fi t analysis at the 0.05 signi fi cance level indicated that the normal distribution function fi tted the EC values of the four transects. Except for transect T(x 1), a lognormal distribution func-tion might also be accepted. A proportional effect stationary semivariogram model: e / (,) () () j j s h x m x h ⎡ ⎤ Φ = ⎣ ⎦ γ γ was fi tted to the local experimental semivariograms g e (h , x j) by the steepest-descent optimization method. The predicted local dispersion variances were reasonable when compared with the experimental variances thereby supporting validity of the proposed model. Statistical analysis of cross validation (kriging) results con fi rmed the adequacy of the stationary semivariogram model and the validity of the estimated parameters. The assumption of quasi-stationary instead of stationary along the transect improved predictions of true kriging variance. The proportional effect quasi-stationary semivariogram models may offer a possible approach for krig handling a regionalized variable having a pronounced trend with-out the need for trend removal.
The adsorption of •87Cs by sediments from the Savannah River Plant follows a theoretically expect... more The adsorption of •87Cs by sediments from the Savannah River Plant follows a theoretically expected linear relationship between In Kd* and 1/T where Kd* and T are the equilibrium distribution coefficient (Cs adsorbed, meg g-VCs + in solution, meq ml-•) and the temperature in kelvins, respectively. The slope of these plots decreases after removal of hydroxy A1 interlayers with citrate pretreatment. Hydroxy AI interlayers thus make Cs + adsorption more temperature dependent. This thermal effect of hydroxy A1 interlayers becomes more significant in sediments containing a:nonswelling 2:1-2:2 intergrade clay mineral than in those containing a swelling 2:1-2:2 intergrade clay mineral. The phenomenon is explained by considering hydroxy A1 interlayers as a source of hydronium ions H80 + which compete with Cs + for exchange positions in wedge zones. An increase in temperature favors an increase in H,O + ions, which in turn favors less adsorption of Cs +. Aside from their thermal effect the positively charged hydroxy aluminum polymeric groups drastically decrease the cation exchange capacity and consequently the adsorption of cesium.
Zeitschrift für Pflanzenernährung und Bodenkunde, 1982
A compilation of some useful approaches used for the obtention of the minimum potential between i... more A compilation of some useful approaches used for the obtention of the minimum potential between interacting flat clay double layers is given. Values of the minimum potential obtained from published nomograms, tables and equations are compared. The effect of dissimilar double layers on the potential is also illustrated. Das elektrische Potential in der Mitte zwischen zwei sich uberlappenden Doppelschichten bei Tonmineralen: Eine Zusammenstellung der theoretischen Ansatze Es wird eine Zusammenstellung nutzlicher Verfahren zur Berechnung des Potentialminimums zwischen flachen, sich gegenseitig beeinflussenden Doppelschichten an Ton gegeben. Werte des Potentialminimums, die mit Hilfe von veroffentlichten Nomogrammen, Tabellen und Gleichungen gewonnen wurden, werden verglichen. Der Einflus von ungleichartigen Doppelschichten auf das Potential wird illustriert.
We demonstrate nearly-spherical, strain-free, self-assembled Ge quantum dots (QDs) fully encapsul... more We demonstrate nearly-spherical, strain-free, self-assembled Ge quantum dots (QDs) fully encapsulated by AlAs, grown on (100) GaAs by molecular beam epitaxy (MBE). The QDs were formed without a wetting layer using a high temperature, in-situ anneal. Subsequent AlAs overgrowth was free from threading dislocations and anti-phase domains. The straddling band alignment for Ge in AlAs promises strong and tunable confinement for both electrons and holes. The reflection high-energy electron diffraction (RHEED) pattern changed from 2×3 to 2×5 with anneal, which can be explained by surface reconstructions based on the electron-counting model.
Proceedings of 2nd International Conference on Recent Advances in Space Technologies, 2005. RAST 2005.
... Thanks to King Faisal University for partial fund. Thanks also extended to Dr. Masoud Abdel A... more ... Thanks to King Faisal University for partial fund. Thanks also extended to Dr. Masoud Abdel Atti, and Dr. Adel Hussain, of Water Studies Center, KFU for their technical assistance. ... [7] Elprince, AM, Turjoman, AM and Al-Dakheel , Y. (1983) Irrigation water requirements for soil ...
The adsorption of trace radioactive cesium by sediments from the Savannah River Plant area follow... more The adsorption of trace radioactive cesium by sediments from the Savannah River Plant area follows a theoretically expected linear relationship between In Kd* and the pH of the equilibrium solution, where Kd* is the equilibrium distribution coefficient: Cs adsorbed (meq g-•)/Cs + in solution (meq ml-•). Theoretically, the slope of these plots is proportional to the fraction of surface area occupied by pH dependent charges. Experimentally, the slope becomes zero after removal of hydroxy AI interlayers with citrate pretreatment. Hydroxy A1 interlayers are thus the main source for the pH dependent charges making Cs + adsorption pH dependent.
ABSTRACT Recording the decrease in weight with time upon heating by elec-trically reproducible in... more ABSTRACT Recording the decrease in weight with time upon heating by elec-trically reproducible infrared (IR) radiation offers a fast method for studying the kinetics of the dehydration of gypsiferous soils. Plotting the weight loss rate against time gives a dehydration curve made of two peaks. The first peak is due to soil moisture and the second to the crystal water of gypsum. The product of dehydration is best regarded as soluble anhydrite (CaSO 4 • e H,O) rather than henii-hydrate (CaSO 4 • iH 2 O) or insoluble anhydrite (CaSO 4). This is in-dicated by the loss in weight and the IR spectra. The kinetic curves for the dehydration of gypsum at 156, 123, and 95°C are of sigmoidal forms. Beyond the inflexion point, most of the data fits the &quot;dimin-ishing sphere&quot; kinetics formula. The rate constants and activation energies for the interface advance process shows that the soil matrix acts as a catalyst and that Na montmorillonite is a more effective catalyst than the soil matrix. A rate-limiting step for the interface advance is the necessity for crystal water to pass through an adsorbed state. Soil minerals may offer effective adsorption sites. In contrast to the growth process soil matrix is a more effective catalyst for nucleation than Na montmorillonite. Additional Index Words: thermodynamics of gypsum dehydration, crystal growth, nucleation.
ABSTRACT Data were obtained at 25°C on the composition of the aque-ous solution and exchanger pha... more ABSTRACT Data were obtained at 25°C on the composition of the aque-ous solution and exchanger phases in NH 4 -Ba-La, La-Ba, La-NH« and Ba-NH 4 aqueous systems comprising the chloride salts of the three cations and a montmorillonite clay from Neva-da. The data for the three binary cation exchange systems were incorporated into a thermodynamic model which was used to predict the composition of the aqueous solution phase of the ternary NH t -Ba-La system as a function of exchanger phase composition. The model employed, known as the sub-regular model, involved a MacLaurin expansion of the ex-changer phase rational activity coefficients to third order in the mole fractions of the exchanger components. The con-stant coefficients in the MacLaurin expansion could be deter-mined solely with experimental data on the infinite-dilution, rational activity coefficients of exchanger components hi binary exchange systems. Thus no data on ternary exchange sys-tems were required to apply the model. The model calcula-tions were in reasonably good agreement with experiment, suggesting that further efforts to predict ternary exchange be-havior from binary exchange data are warranted. Additional Index Words: exchanger phase activity coeffi-cients, thermodynamics of cation exchange.
Accurate prediction of the leaching requirements (Lr) of crops and striving to attain them is ess... more Accurate prediction of the leaching requirements (Lr) of crops and striving to attain them is essential for efficient irrigation water use. Solute modeling was extended to develop four Lr conceptual models that do not neglect solute reactions in the root-zone, surface evaporation, and the influence of immobile wetted pore space. The models were based on: (i) the water movement equation
Landsat TM5 still provide useful information about earth surface features although there are more... more Landsat TM5 still provide useful information about earth surface features although there are more advanced sensors with high capability of scanning and processing of remotely sensed data. In this respect, Landsat TM5 data were used to map saline soil and vegetation in one of the largest irrigated oases in the world. The study area is Al-Hassa oasis located in the southern part of the eastern region of Saudi Arabia. Main cultivated crops in the Al-Hassa area are date palm, alfalfa, vegetables, and some fruits. The most serious problem in the region is soil salinity that develop as a result of natural soil forming processes. The lack of the amount of irrigation water for cultivation raise the requirements to have proper management methods and adequate planning for the area. For the amelioration of salt affected soils and their effective utilization for successful plant production, it is necessary to establish rigorous management and frequent monitoring for these area. This research aimed to classify the vegetation in the scene image and to identify salt-affected soils in the study area. Two landsat TM5 images were used in this research. NDVI was calculated as a ratio between measured reflectivity in the red and near infrared bands. These two spectral bands are chosen because they are most affected by the absorption of chlorophyll in leafy green vegetation and by the density of green vegetation on the surface. Also, in red and near-infrared bands, the contrast between vegetation and soil is at a maximum. Therefore, NDVI relatively provided good results in classification of salt-affected and in distinguishing between vegetation classes.
A relatively rapid method based on using radioactive ions as tracers was developed for obtaining ... more A relatively rapid method based on using radioactive ions as tracers was developed for obtaining adsorption isotherms.' Cesium-Na adsorption isotherms were deter-mined for the < 100~-t fraction of two sediments before and after the removal of hydroxy Al interlayers with citrate. Removal of the interlayers from the sediment characterized with swelling 2:1-2:2 intergrade, while increasing the capacity to adsorb Cs, decreased Cs selectivity, the standard free energy change, and the density of surface charge. Such decreases were insignificant for the other sediment characterized with non-swelling 2:1-2:2 intergrade .
The adsorption of 137/sub Cs/ by sediments from the Savannah River Plant follows a theoretically ... more The adsorption of 137/sub Cs/ by sediments from the Savannah River Plant follows a theoretically expected linear relationship between ln Kd and l/T where kd and T are the equilibrium distribution coefficient and the temperature in kelvins, respectively. The slope of these plots decreases after removal of hydroxy Al interlayers. Hydroxy Al interlayers thus make Cs/sup +/ adsorption more temperature
ABsTRACT. Investigation of the origin of chemical composition of drainage water, accurate estimat... more ABsTRACT. Investigation of the origin of chemical composition of drainage water, accurate estimation of leaching requirement, and simulation of crop yield response are essentials for effective re-utilization of drainage water for irrigation and salinity control. The comprehensive chemical model SAO (for the chemical evolution of drainage waters and soil solutions) and the leaching requirement model LrSAO-e (for reactive salt), were verified using a new set of data. The new data are the results of water and soil analysis carried out in a pilot farm during leaching reclamation and by sampling an extension area in AI Hassa, Saudi Arabia. The steady-state SAO model was, originally, based on the changes in irrigation water composition, which occurred due to molecular-water loss, mineral precipitation and di ssolution, K+ fixa-tion, NaCI apparent retention, MgS04' formation, and biological formation of HCO) . Better model predictions were obtained by including CaS04' formation, an...
Soil sampling locations are, often, determined by visual estimations obtained from a base map. Oc... more Soil sampling locations are, often, determined by visual estimations obtained from a base map. Occasionally, one may need to use a map that contains little or no coordinate information. This is a problem if he intends to register this map with another in a multilayer database. In this paper we used the coordinates of selected ground control points (GCPs) obtained with a Trimble GPS unit to transform (register) the base map (1:10000 scale of unknown coordinate system) digitized in units of the base map into metric UTM system. Registration was done using affine transformation in ARCIINF GIS. The accuracy of this procedure was analyzed by comparing the GPS positions of one-way-roads with their corresponding GIS transformed positions. A 45-m buffer was required for at least 95% of the GIS roads to occupy the same GPS road positions. Thus, any resulted soil coverage map should be at a lower scale than the base map with a scale of 1: 45000 as an upper limit. Error budget analysis indicate...
Abstract The success of field fertilizer trials depends, largely, upon the selection of sites of ... more Abstract The success of field fertilizer trials depends, largely, upon the selection of sites of wide range in deficiencies for the nutrients under investigation. The date palm (Phoenix dactylifera L.,) cultures of AI Hassa region were grid-surveyed for appropriate sites to conduct field trials by P and K soil testing of 12,000 ha and 9,200 ha, respectively. The "NaHC0 3 (0.5 M) pH 8.5" and the "NH 4 AOc (1 M) pH 7" soil testing methods were used for P and K, respectively. Soil sampling involved the collection of two random composite soil samples (0-20 em depth) for each site. The 'T' composite was at a distance 1 m from the date palm stem and the 'U' composite represented the soil in between the date palms (inter-planted soils). The soil test values were grouped, based on approximate critical soil test levels, C (= 5 mg p/ kg soii for P and 60 mg K /kg soil for K) into five categories: probable response class (0 -2C), low residual class (2C -4C),...
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