Showing papers in "Soil Science in 1984"
TL;DR: In this article, the authors measured dissolved organic carbon (DOC) in soil solutions collected from the A and B horizons of a Spodosol in central New Hampshire and found that DOC averaged 33 mg/L in the A2 horizon and declined to 2 to 3 mg/l in the B horizon.
Abstract: We measured dissolved organic carbon (DOC) in soil solutions collected from the A and B horizons of a Spodosol in central New Hampshire. DOC averaged 33 mg/L in the A2 horizon and declined to 2 to 3 mg/L, similar to stream water concentrations, in the B horizon. DOC concentrations in A2 hori
345 citations
TL;DR: The dependent-domain theory of hysteresis developed here accounts for the effect of the pore-water blockage against air entry while using the similarity hypothesis of the universal model, and seems to agree with observations much better that Model II, which uses the same amount of data for calibration.
Abstract: The dependent-domain theory of hysteresis developed here accounts for the effect of the pore-water blockage against air entry, while using the similarity hypothesis of the universal model (Mualem 1977). The resulting model is simpler and requires fewer data for calibration than previous depe
157 citations
TL;DR: The authors studied the forms, properties, and significance of active Al and Fe in the humus horizons of Andosols from northeastern Japan and formed a hypothesis to elucidate the surface weathering of volcanic ash.
Abstract: We studied the forms, properties, and significance of active Al and Fe in the humus horizons of Andosols from northeastern Japan and formed a hypothesis to elucidate the surface weathering of volcanic ash.Our soil samples were divided into two groups: nonallophanic and allophanic. Nonallopha
154 citations
TL;DR: In this paper, the type, pH optima, kinetic parameters (Km and Vmax), and activation energies (Ea) of phosphatases in soils and organic waste materials were compared.
Abstract: Phosphatases catalyze reactions important in P cycling in soils and for plant nutrition. We carried out this study to compare the type, pH optima, kinetic parameters (Km and Vmax), and activation energies (Ea) of phosphatases in soils and organic waste materials. Results showed that plant ma
128 citations
TL;DR: In this paper, the authors report changes in the content of nitrogen and organic carbon in the dark-colored soil on the Morrow plots during 70 years, 1904 to 1973, under different cropping systems and soil treatments.
Abstract: The Morrow Plots, which were established in 1876 at Urbana, Illinois, are the oldest experimental plots in America, and they contain the longest continuous corn (Zea mays L.) plot in the world. This paper reports changes in the content of nitrogen and organic carbon in the dark-colored soil on the Morrow Plots during 70 years, 1904 to 1973, under different cropping systems and soil treatments. In comparison with continuous corn culture, crop rotations retarded the decline in soil nitrogen and organic carbon. However, crop rotations without soil treatment did not maintain the soils in a high state of productivity. Crop rotation plus appropriate fertilization produced the highest crop yields and also maintained soil nitrogen and organic carbon at the highest levels.
125 citations
TL;DR: In this article, a synthesis of information available on the adsorption of polycyclic aromatic hydrocarbons (PAH) in water/soil systems is presented, and an analysis of how limited PAH data for PAH on soils may be used in conjunction with PAH molecular characteristics to predict PAH properties for a wide range of PAH and soils.
Abstract: This paper presents a synthesis of information available on the adsorption of polycyclic aromatic hydrocarbons (PAH) in water/soil systems. Included is an analysis of how limited adsorption data for PAH on soils may be used in conjunction with PAH molecular characteristics to predict adsorption properties for a wide range of PAH and soils. Also presented is an evaluation of procedures that enable prediction of adsorption characteristics of PAH on soils based on soil organic carbon content and physical chemical or structural characteristics of the particular compound. 60 references, 4 figures, 4 tables.
121 citations
TL;DR: In this paper, a simplified soil temperature model was developed to predict hourly and daily maximum and minimum soil temperatures under different amounts of plant cover, and the model requires daily maximum temperature (2 m), plant biomass, initial soil temperature, an
Abstract: This paper reports a simplified soil temperature model, developed to predict hourly and daily maximum and minimum soil temperatures under different amounts of plant cover. As input the model requires daily maximum and minimum air temperature (2 m), plant biomass, initial soil temperature, an
104 citations
TL;DR: In this paper, the authors used SAR as an index of sodicity and related physical phenomena of clay dispecifics. But SAR does not take into account the cations of the anionic species and ignores the alkali-causing species.
Abstract: Excess exchangeable sodium is known to adversely affect soil's physical properties. Sodium adsorption ratio (SAR), which takes into account only the cations, ignoring the alkali-causing anionic species, has been widely used as an index of sodicity and related physical phenomena of clay dispe
103 citations
TL;DR: In this paper, the authors present a variance analysis for quantifying the different sources of errors induced on volumetric water content measurements and calculation of soil water storage with the use of a neutron moisture meter in one single access tube.
Abstract: We present a variance analysis for quantifying the different sources of errors induced on volumetric water content measurements and calculation of soil water storage with the use of a neutron moisture meter in one single access tube. For comparative purposes, we apply the analysis to field data obtained with two different probes. In each case the calibration curve is established by measuring simultaneously and independently neutron count rates and corresponding water contents. Two different approaches are considered, i.e. the unbiased treatment and the biased treatment. The unbiased treatment differs from the biased by its correction for measurement errors using the leastsquare technique. For the site under consideration, we show that the calibration component is the major contribution to the total variance associated with an individual water content estimation. The use of the unbiased statistical treatment notably decreases the total variance. In cases where the calibration curve is established very accurately, the instrument component can be reduced by increasing the number of count replications at each sampling point or the counting time or both. The loss of precision due to using neutron count rate ratios instead of simple count rates is negligible if several count replications are made in a standard medium or if the counting time is long enough. We show that the rule of integration of water content profiles in order to calculate water storage has a great importance: the use of Simpson's rule drastically decreases the associated variance as compared with the classical trapezoidal method.
102 citations
TL;DR: In this article, the loss of nitrate fertilizer via denitrification was simulated using a mathematical model that included transport and plant uptake of water and nitrogen in soil, and different rate coefficients were assigned for each stage and carbon source.
Abstract: Losses of nitrate fertilizer via denitrification were simulated using a mathematical model that included transport and plant uptake of water and nitrogen in soil. The denitrification rate was considered to be a function of nitrate concentration, water-extractable organic carbon concentration, degree of soil-water saturation, and temperature. Water-extractable organic carbon concentrations were calculated from initial amounts of soil carbon and additions of plant residues or animal manure. It was assumed that the consumption of added carbon in the soil system would occur in two or three stages and different rate coefficients were assigned for each stage and carbon source. A Q/sub 10/ value of 2 was used in correcting the rate coefficients for denitrification were compared with measured N/sub 2/ and N/sub 2/O gas fluxes at the soil surface during nitrate leaching in field plots of Yolo soil maintained at different soil-water content and soil temperatures and that received various carbon additions and irrigation frequencies. Reasonable agreement was found between measured rates and total amounts of denitrification and those calculated by the model using a single denitrification rate coefficient for all cropped field plots and another rate coefficient for all uncropped field plots. 32 references, 6 figures, 3 tables.
94 citations
TL;DR: In this article, the authors used first-order, Elovich, parabolic diffusion, and zero-order equations to describe the kinetics of K-Ca exchange in the Atlantic Coastal Plain Region.
Abstract: We used first-order, Elovich, parabolic diffusion, and zero-order equations to describe the kinetics of K-Ca exchange in kaolinite, montmorillonite, vermiculite and soils of the Atlantic Coastal Plain Region. The first-order equation was the best of the various kinetic equations studied to describe the reaction rate of K adsorption in the clay minerals and soils, as evidenced by the highest simple correlation coefficients (r) and the lowest values of the standard error of the estimate (SE). The parabolic diffusion law described K adsorption best on vermiculite and soils dominated by vermiculitic clay minerals. The parabolic diffusion law did not describe K adsorption well on kaolinite and soils high in kaolinite. These differences were related to the kinds of binding sites present in the pure and mixed systems. The Elovich and zero-order equations did not satisfactorily describe K adsorption in the soils and clays. Apparent potassium adsorption rate coefficients (ka/) were 0.23, 0.58, and 2.65 h-1 for vermiculite, montmorillonite, and kaolinite, respectively. The ka/ values for the soils ranged from 0.84 to 1.86 h-1, and their magnitude was related to the type and quantity of clay minerals present.
TL;DR: In this paper, the relative importance of sesquioxides, organic matter, and a series of particle size fractions in adsorbing atrazine was investigated in two Saskatchewan soils.
Abstract: We used two Saskatchewan soils to investigate the relative importance of sesquioxides, organic matter, and a series of particle size fractions in adsorbing atrazine. The DCB (sodium dithionite-citrate-bicarbonate)-extractable Al and Fe are associated with a series of soil particle size fract
TL;DR: In this article, the relative effects of common northern Idaho cultural practices (tillage methods, crop rotations, and N fertilizer rates) on the acidification of a northern Idaho soil were investigated.
Abstract: Soils in northern Idaho are exhibiting a rapid decline in pH. In undertaking this study, we sought to determine the relative effects of common northern Idaho cultural practices—tillage methods, crop rotations, and N fertilizer rates—on the acidification of a northern Idaho soil. The plots were established north of Moscow, Idaho, in 1974 and evaluated no-till, minimum tillage, and conventional tillage treatments and three-crop rotation systems: (1) a 2-year winter wheat (Triticum aestivum L. cv. Nugaines)-spring pea (Pisum sativum cv. Alaska) rotation; (2) a 3-year winter wheat-spring wheat (Triticum aestivum L. cv. Fieldwin)-spring pea rotation; and (3) a 3-year winter wheat-alfalfa (Medicago sativa L. cv. Ladak) red clover (Trifolium pratense cv. Kenland) peaalfalfa red clover rotation. The plots were split by N application rates and sampled by depth. When sampled by 300-mm increments, depth was the only factor that affected soil pH. Soil pH increased with increasing depth. There was a statistically unique calcium chloride pH at each sampling depth down to 1500 mm. When the surface 300 mm was sampled by 75-mm increments, the interaction of crop rotation x tillage x N rate x depth was significant. It was apparent that N rates were the major influence on pH differences. Crop rotations influenced the amount of N fertilizer required for crop production and consequently affected the magnitude of the pH decline. Tillage influenced the placement of N fertilizer and consequently the location and depth of acidification in the soil profile. The greatest acidification under no-till management occurred in the surface 75 mm, under minimum tillage at the 75-to 150-mm depth, and under conventional tillage in the surface 250 mm. A significant decrease in pH was observed in all treatments over the 8-year period.
TL;DR: Etude experimentale sur l'effet de la pression de l'air et le infiltration of l'eau dans une colonne de sol verticale as mentioned in this paper.
Abstract: Etude experimentale sur l'effet de la pression de l'air sur l'infiltration de l'eau dans une colonne de sol verticale
TL;DR: In this article, the effects of organic matter and oxides of Al and Fe on sulfate adsorption by an iron podzol and a brown earth were studied by evaluating the differences in sulfate adaption with and without these soil constituents.
Abstract: The effects of organic matter and oxides of Al and Fe on sulfate adsorption by an iron podzol and a brown earth were studied by evaluating the differences in sulfate adsorption with and without these soil constituents. The removal of organic matter had little effect on sulfate adsorption but the removal of Al and Fe oxides had a marked reduction in sulfate adsorption capacity of the iron podzol. The reduction in sulfate adsorption by this soil, due to the removal of Al or Fe, was higher at low concentrations of sulfate in solution. The effect of Al and Fe removal on sulfate adsorption in the brown earth was relatively small and observed only at low concentrations of sulfate in solution. 15 references, 2 figures.
TL;DR: The relationship between surface area and rate of oxidation of Fe sulphides (pyrite and marcasite) separated from Texas lignite was studied in this paper, where reaction kinetics with respect to Fe sulphide morphology and particle size were evaluated.
Abstract: The relationship between surface area and rate of oxidation of Fe sulphides (pyrite and marcasite) separated from Texas lignite was studied. The reaction kinetics with respect to Fe sulphide morphology and particle size were evaluated. The oxygen concentration and the presence of autotrophic Fe and S-oxidizing bacteria (thiobacillus ferro-oxidans) on the rate of oxidation were also evaluated. The formation of sulphate from Fe sulphide was selected to measure the rate of oxidation. Relative reaction rates for different morphological forms of Fe sulphide were: marcasite > framboidal pyrite > massive pyrite. As the surface area of pyrite doubled, reaction rate increased by a factor of 1.5. Sulphate production for the 5 to 2 ..mu..m fraction was twice that of the 50 to 20 ..mu..m fraction. Reaction rate was approximately fivefold greater for non-inoculated treatments at 20% O/sub 2/ compared with 0% O/sub 2/ and was approximately ninefold greater for the same treatment inoculated with T. ferro-oxidans.
TL;DR: In this paper, the effects of soil type, N concentration, organic matter, moisture regime, CaCO3, and temperature on urease activity and kinetics of urea transformation were studied in a series of laboratory incubation experiments.
Abstract: The effects of soil type, N concentration, organic matter, moisture regime, CaCO3, and temperature on urease activity and kinetics of urea transformation were studied in a series of laboratory incubation experiments. Urease activity ranged from 19.0 to 26.1 tig urea-N hydrolyzed/g soil/h at 37°C. Increase in N levels, temperature up to 35°C, and moisture content, up to field capacity linearly increased urease activity of three selected soils, and addition of CaCO3 up to 8% decreased it considerably. There was no effect of undecomposed grasses, but decomposed organic matter increased soil urease activity. Urea transformation followed first-order kinetics, and the rate of urea hydrolysis increased with temperature in the three soils. Thermodynamic properties (energy of activation, free energy, entropy) were calculated for selected soils.
TL;DR: The authors examined the relationship between soil bulk density values and organic and mineral contents for two large data sets collected in a wide range of sediment and marsh types in Louisiana, and found that organic carbon contents varied between < 4 and 43%.
Abstract: We examined the relationships between soil bulk density values and organic and mineral contents for two large data sets collected in a wide range of sediment and marsh types in Louisiana. Bulk densities ranged from 0.05 to 0.60 g/ml, and organic carbon contents varied between < 4 and 43%. Bu
TL;DR: This article examined a rhyolitic volcanic ash bed deposited 20000 years ago in different leaching environments in New Zealand and found that allophane with a 1/Si ratio close to 2 forms in strongly leached environments, possibly because Si in the soil solution is low.
Abstract: We examined a rhyolitic volcanic ash bed deposited 20000 years ago in different leaching environments in New Zealand. When winter leaching was greater than 250 mm a year, the ash contained 10 to 15% allophane; as leaching increased from 250 to 600 mm a year, the A1/Si ratio of the allophane increased from 1.2 to 2.0. When the leaching was < 250 mm a year and water movement was somewhat restricted, the allophane content of the bed was very low, and halloysite was the predominant clay mineral. The results support a hypothesis that allophane with A1/Si ratio close to 2 forms in strongly leached environments, possibly because Si in the soil solution is low; halloysite forms in weakly leached environments, possibly where Si in soil solution is more concentrated.
TL;DR: In this paper, the authors studied sulfate adsorption by four acid forest soils to determine the adaption capacities of these soils and to compare different adsorsorption equations.
Abstract: We studied sulfate adsorption by four acid forest soils to determine the adsorption capacities of these soils and to compare different adsorption equations in describing sulfate adsorption. The adsorption capacity of the iron-podzols (P1 and P5) was nearly double that of the semipodzol (P4) and the
TL;DR: This article developed a simulation model, NFLOOD, for describing simultaneous partitioning, transformations, and transport of nitrogen in flooded soils and selected cases were simulated using NFLOOD to identify the relative gaseous losses of soil and fertilizer via denitrification and NH3 volatilizati.
Abstract: We developed a simulation model, NFLOOD, for describing simultaneous partitioning, transformations, and transport of nitrogen in flooded soils. Selected cases were simulated using NFLOOD to identify the relative gaseous losses of soil and fertilizer N via denitrification and NH3 volatilizati
TL;DR: In this article, the authors examined the influence of soil-water tension and soil temperature on 14C-2,4D degradation and the formation of nonextractable residues.
Abstract: In laboratory studies on Cecil loamy sand and Webster sandy clay loam, I examined the influence of soil-water tension and soil temperature on 14C-2,4-D degradation and the formation of nonextractable 14C-residues, and I correlated the degradation rate with the growth rate of 2,4-D degrading microorganisms 14C-2,4-D rapidly mineralized in the two soils maintained at 01 and 033 bar of soil-water tension Because the total amounts of metabolites in the solvent extracts never exceeded 5% of the total 14C activity, the disappearance rate of extractable 14C essentially represented the disappearance rate of extractable 14C-2,4-D Extractable 14C in the 14C-2,4-D treated soils maintained at 1 bar and below disappeared rapidly, and at the same time nonextractable 14C rapidly formed, whereas extractable 14C in soils maintained at 15 bars disappeared at much slower rates, and the formation of nonextractable 14C was also slower After 14 d of slow disappearance, however, extractable 14C in the Cecil soil held at 15 bars started disappearing at a constant rate of 36% of applied 14C per day The disappearance rates in soils incubated at 35°C were generally smaller than those incubated at 25°C Even though the initial most probable number (MPN) of 2,4-D degrading microorganisms in the Cecil soil was one fourth of that in the Webster soil, the organisms propagated more rapidly in the moist Cecil soil (033 bar) than in the moist Webster soil in response to the application of 10 μg 2,4-D/g of soil As a result, 2,4-D in the Cecil soil degraded at a faster rate The growth rates of 2,4-D degrading organisms in dry soils (15 bars) were small, in spite of the rapid degradation occurring in the Cecil soil after 14 d of incubation In addition to forming nonextractable 14C residues in humus components, as much as 42% of applied 14C could be associated with microbial mass
TL;DR: In this article, the level, chemical fractions, and solubility of Pb in several roadside soils of heavily traveled areas of Caracas, Venezuela were investigated using 1 N HNO/sub 3/ extraction.
Abstract: The author investigated the level, chemical fractions, and solubility of Pb in several roadside soils of heavily traveled areas of Caracas, Venezuela. Using 1 N HNO/sub 3/ extraction, he studied the levels of lead in 25 roadside soil samples and found a very high level of Pb (average enrichment factor 21.0), indicating a strong lead pollution of Caracas roadside soils by heavy traffic of motor vehicles. Lead accumulation was most localized in the top soil layer (0 to 5 cm) and in soils located within 1 m from the roadside. Chemical fractionation and solubility experiments on three surface soil samples containing high Pb levels showed that less than 0.7% Pb was in exchangeable form in these soils. The nonexchangeable Pb was found to be associated mainly with the organic and residual fractions in two of the three soils, and predominantly bound specifically to inorganic sites in the third soil. The amount occluded in iron oxides was low in the three studied soils. Solubility studies showed Pb to be less soluble at higher pH values and pointed to a direct relationship between total and exchangeable Pb content and solubility. In the soils studied Pb seems to be associated with several soilmore » components by different sorption mechanisms acting concurrently, the predominant mechanism or mechanisms being stronger than normal ion exchange. This behavior was considered to have practical implications, such as low Pb mobility in the soil profile, as well as low availability to plant roots and soil biota.« less
TL;DR: In this paper, the authors investigated the kinetics of sulfate adsorption and the effects of temperature and moisture on sulfate sorption of two acid forest soils, and showed that longer contact between soil and sulfate ions and higher temperature will result in immobilization of atmospherically deposited sulfate in these soils, whereas increased moisture content will result to mobilization of sulfates and cations.
Abstract: The kinetics of sulfate adsorption and the effects of temperature and moisture on sulfate sorption of two acid forest soils have been investigated. Sulfate adsorption in both soils was time-dependent and showed an excellent fit, accounting for more than 99% of the variation, by a two-constant rate equation x = K/sub a/C/sub o/t/sup 1/m/ where x = adsorbed sulfate, C/sub o/ = initial sulfate concentration, K/sub a/ = rate coefficient, t = time, and 1/m = constant. The average rate coefficients of sulfate adsorption over a period of 1152 h were 0.462 and 0.167 h/sup -1/ for the iron-podzol and brown-earth soils, respectively. Thus the relative rate was faster in the iron podzol than in the brown earth. The rate of sulfate adsorption was faster initially (up to 4 h), but decreased drastically with increased time. Sulfate adsorption over a period of 1152 h in both soils showed the best fit, accounting for more than 99.9% of the variation, by a multiple-order kinetic equation dx/dt = Kx/sup n/ where x and t are the same as in the rate equation, and K and n are constants. Sulfate adsorption in both soils increased over a temperature range of 4 to 24/supmore » 0/C, but it decreased when the moisture content of the soils was raised from 5 to 100% on an oven-dry weight basis. The percentage of sulfate desorbed decreased with increase in time and temperature, but it increased with increased moisture content. These results indicate that longer contact between soil and sulfate ions and higher temperature will result in immobilization of atmospherically deposited sulfate in these soils, whereas increased moisture content will result in mobilization of sulfate and cations. 23 references, 5 figures, 2 tables.« less
TL;DR: In this article, the authors examined the desorption of adsorbed sulfate by acid forest soils and its potential losses due to acid precipitation, and determined the extent to which sulfate was desorbed by water, dilute HCl, and Ca(NO/sub 3/)/sub 2/ ).
Abstract: To examine the fate of adsorbed sulfate by acid forest soils and its potential losses due to acid precipitation, desorption of adsorbed sulfate was determined as a function of time, soil:solution ratio; desorbing ion, pH, and amount of adsorption. Desorption of sulfate was very rapid and completed within half an hour. Sulfate desorption by water, dilute HCl, and Ca(NO/sub 3/)/sub 2/ was inversely related to the ability of the soils to adsorb SO/sub 4//sup -2/, but it was found to increase with increasing pH and the amount of adsorption. The very low desorption of SO/sub 4//sup -2/ in the iron-podzol by either water or Ca(NO/sub 3/)/sub 2/ at pH below 5.0 suggests that the adsorbed SO/sub 4//sup -2/ will be highly resistant to acid leaching, but it may also be less available to plants. The proportion of specifically adsorbed SO/sub 4//sup -2/ was higher in the iron-podzols than in the semipodzol and brown-earth, but it decreased with increasing pH and the amount of adsorption. Sulfate desorbed by Ca(H/sub 2/PO/sub 4/)/sub 2/ was least affected by the nature of adsorbing complex, pH, and amount of adsorption, indicating that phosphate is able to desorb SO/sub 4//sup -2/ adsorbed due to either permanentmore » or pH-dependent charges. 23 references, 3 figures, 2 tables.« less
TL;DR: The Microtrac method is particularly well suited to particle-size analysis of suspended sediment samples having low concentrations and limited quantities, because quantities of 0.01 g may be routinely analyzed.
Abstract: The Microtrac method is particularly well suited to particle-size analysis of suspended sediment samples having low concentrations and limited quantities, because quantities of 0.01 g may be routinely analyzed. Major advantages of the Microtrac method are the speed and ease with which the me
TL;DR: Sewage sludge was added annually for 6 years to a series of field plots at rates varying from 0 to 225 metric tons per hectare per year as mentioned in this paper, and the sludges were mixed into the surface 20 cm of soil.
Abstract: Sewage sludge was added annually for 6 years to a series of field plots at rates varying from 0 to 225 metric tons per hectare per year. The sludges were mixed into the surface 20 cm of soil. The data published here cover the last 4 years. The metals increased in the surface soil with sludge rate and with years of addition. Metal movement, within the profile, was limited to a depth of 5 cm below the zone of sludge incorporation for cadmium, copper, and lead. Zinc moved 5 to 10 cm deep. DTPA/HNO/sub 3/ ratios for a given metal are nearly constant over the 4-year period and also at all depths. Relative availability of metals in the surface soil was Cd = Cu > Pb = Zn for Pacheco sludge-treated soils and Cd > Zn > Cu > Pb for the Oakland sludge-treated soils. 31 references, 4 figures, 5 tables.
TL;DR: In this article, the authors measured thermal conductivity for Berino sand packed into columns, using the line heat source method described by de Vries (1952a), and compared their measured values with those measured in columns packed with premoistened soil.
Abstract: We determined values of thermal conductivity for Berino sand packed into columns, using the line heat source method described by de Vries (1952a). The microwave oven technique of Horton et al. (1982) was used to bring the soil in the columns to a predetermined water content. We then compared our measured values of thermal conductivity with those measured in columns packed with premoistened soil (Westcot 1972). At water contents below 0.10 cm3/cm3, we found poor agreement between the values of thermal conductivity, which we attributed to the manner in which columns were packed with soil. Columns with larger bulk density were found to have substantially larger values of thermal conductivity in the range of water contents from ovendry to 0.10 cm3/cm3. We also compared our measured values of thermal conductivity with values calculated using the method described by de Vries (1963). There was better agreement between our measurements and the calculations than was found by Westcot (1972). In both cases, however, the agreement was relatively poor. When we used the shape factors for air or solids similar to those of Kimball et al. (1976), the agreement between calculated thermal conductivity and values measured in this study improved.
TL;DR: The authors evaluated four different soil-water extractor cup materials to determine the amount of soluble ortho-phosphate adsorbed by the cup during soil water sample collection and determined desorption for selected cups, after equilibrium had been reached.
Abstract: We evaluated four different soil-water extractor cup materials to determine the amount of soluble ortho-phosphate adsorbed by the cup during soil-water sample collection. We also determined desorption for selected cups, after equilibrium had been reached, during the adsorption tests. Teflon and the fritted glass extractor cups exhibited insignificant adsorption, but the alundum and Soil-Moisture ceramic cups were found to adsorb and desorb large amounts of phosphorus.1 Acid-washing the cups with 1 N HC1 solution prior to testing significantly increased the amount of adsorption and, to a lesser degree, desorption of phosphorus.
TL;DR: In this paper, the effects of four different methods of land clearing in western Nigeria on soil physical properties of an Alfisol and on the root growth of the following crop were studied.
Abstract: We studied the effects of four different methods of land clearing in western Nigeria on soil physical properties of an Alfisol and on the root growth of the following crop. The methods used were manual clearing and clearing with a shearblade, a treepusher, and a treepusher/root rake. Soil physical properties measured were bulk density, saturated hydraulic conductivity, infiltration rate and cumulative infiltration, total porosity, pore size distribution, and soil water retention. Mechanical clearing increased bulk density and proportion of medium-sized pores (2 to 14.3-μm radius) and decreased infiltration rate, cumulative infiltration, saturated hydraulic conductivity, total porosity, and proportion of macropores (>14.3-μm radius). Soil water content at a potential of 0 kPa was significantly reduced, whereas that at potentials of –10 and –33 kPa was increased. In comparison with the forested control, the magnitude of changes in soil physical properties was in the order of manual clearing < treepusher < shearblade < treepusher/root rake. Although the differential effects of land clearing methods on the soil were reflected only in the initial pattern of maize root growth during the seedling stage, it was sufficient to affect grain yield. Root growth of mucuna and cowpea were not affected by the changes in soil physical properties.