EFFECT OF pH ON ELECTRIC CHARGES CARRIED BY CLAY PARTICLES

Schofield, R. K.

doi:10.1111/j.1365-2389.1950.tb00713.x

Cited by 209 publications

(72 citation statements)

References 6 publications

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“…3). The hydraulic conductivity at pH 7.0 was 0.27 cm/hr, or more than t,wice that at pH 8.0, and the hydraulic conductivity at pH 6.5 was 0.95 cm/hr, or seven times that at pH 8 (9). The large anomalous increase encountered at pH 8.0 was unexpected.…”

Section: Introductionmentioning

confidence: 82%

INFLUENCE OF SOIL pH ON SURFACE CHARGE AND WATER TRANSMISSION

Sommerfeldt¹,

Schaik²

1971

Can. J. Soil. Sci.

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The effects of pH were determined on the was not the same for both. The electroexchangeable Na and electrophoretic mobility phoretic mobility of the loam increased of Na-saturated bentonite from Greybull, 284Vo from pH 6.0 to 8.0, whLile that of the Wyoming, and Na-saturated Lethbridge loam bentonite increased 53Vo. T}rtt water transand on the water transmission of the Leth-mission of the loam at pH 6'5 and 7.0 was bridge loam. The data obtained were related seven times and twice, respectively, that at to problems of reclaiming an alkaline-sodic pH 8.0. It was concluded that lowering the soil. The exchangeable Na of the bentonite pH of an alkaline-sodic soilL may be an and the loam increased about 507o from pH effective means of enhancing its reclamation.

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Section: Introductionmentioning

confidence: 82%

INFLUENCE OF SOIL pH ON SURFACE CHARGE AND WATER TRANSMISSION

Sommerfeldt¹,

Schaik²

1971

Can. J. Soil. Sci.

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“…After percolation the suction is maintained at 0.1 bar for half an hour and the tube is weighed to obtain the wet weight (G 2 ). The average amount of retained solution amounted to about 1 ml per gram of soil as compared to 2 ml per gram of soil after centrifugation (Schofield, 1949). d. Stripping step.…”

Section: Methodsmentioning

confidence: 96%

“…Calculation of adsorption capacities. With systems containing only one type of cations and anions, CEC and AEC are calculated according to CEC =Teat-S and AEC =Tan-S, where Tis the total amount of cations or anions in the system and Sis the amount of neutral salt in solution (S =Scat= San• Schofield, 1949). S is calculated by multiplying the volume of solution retained in the system with the salt concentration as measured in the free solution.…”

Section: A Further Complication Is That Certain Ions Like Ca2+ Andmentioning

confidence: 99%

The cation‐ and anion exchange characteristics of soils with a large sesquioxide surface area

Koenigs

Leffelaar²,

Breimer³

et al. 1981

J Plant Nutrition & Soil

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The theory on colloids with a pH‐dependent surface potential indicates that the anion exchange capacity of soils containing hematite or similar oxides depends on pH, electrolyte concentration and valency of counterions. These relationships were tested for the salinity‐ and pH‐range of importance to agriculture, using a percolation technique. MgSO4 was chosen as impregnating salt to minimize the overall error caused by salt exclusion. The assumptions on the anion exchange behaviour proved to be correct; moreover they applied also to a considerable fraction of the cation exchange. The results were formulated in terms of multiple linear regression equations relating the exchange capacities to pH and the square root of the electrolyte concentration. Consequently, the adsorption behaviour of ferruginous soils can not be characterized by the determination of CEC and AEC at one level of pH‐ and salt concentration in solution. Due to the inefficiency of the ethanol washing step, two standard methods overestimated CEC by a factor 2 to 4.

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“…Soil C:N ratio was determined on oven-dried ground soil samples using a TruSpec® Analyzer (Leco Corp., St. Joseph, MI). The cation exchange capacity (CEC) of soils was determined using an unbuffered salt extraction method of Schofield (1949). Soil pH and electrical conductivity (EC) were measured using standard electrodes (1:2.5 (w/v) soil-to-distilled water).…”

Section: Soil and Sheep Urine Analysismentioning

confidence: 99%

The mobility of nitrification inhibitors under simulated ruminant urine deposition and rainfall: a comparison between DCD and DMPP

et al. 2016

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Urine patches within pasture soils are hotspots for nitrogen (N) cycling and losses, where nitrification inhibitors (NI) offer a means of reducing such losses. Within urine influenced soil, more research has been conducted for dicyandiamide (DCD) than 3,4-dimethylpyrazole phosphate (DMPP). Differences in the efficacy of these NI are often ascribed to a greater mobility of DCD, which may lead to spatial separation from NH 4 + and nitrifying microorganisms. We tested the mobility of 14 C-labelled DCD and DMPP relative to sheep urine-derived NH 4 + in soil columns of contrasting texture and organic matter content, following simulated rainfall. We also assessed factors influencing the vertical mobility of these NI in soils, including solubility, sorption/ desorption processes and microbial degradation and uptake. Following 40-mm rainfall, without the presence of sheep urine, the distribution of both NI were similar in the soil columns; however, there was a greater retention of DCD compared to DMPP in the top 1 cm. Both NI appeared to co-locate well with urine-derived NH 4 + , and the presence of sheep urine altered the leaching profile of the NI (compared to rainfall application alone), but this effect was inhibitor and soil-type dependent. A greater sorption to the soil matrix was observed for DCD in comparison to DMPP in all three studied soils, and the presence of urine generally increased desorption processes. Of the NI applied to the soil columns, 18-66 % was taken up within 30 min by the microbial community. However, only small amounts (<1 %) were mineralized during this period. In conclusion, due to the greater adsorption of DCD as opposed to DMPP and similarity in the degree of co-location of both NI with urine NH 4 + , the results of this study suggest that differences in microbial uptake and degradation may be more important parameters for explaining differences in the efficacy of reducing nitrification. Further work is required to determine the comparative efficacy of both NI in reducing nitrification rates under field conditions in a range of soil types and environmental conditions.

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EFFECT OF pH ON ELECTRIC CHARGES CARRIED BY CLAY PARTICLES

Cited by 209 publications

References 6 publications

INFLUENCE OF SOIL pH ON SURFACE CHARGE AND WATER TRANSMISSION

INFLUENCE OF SOIL pH ON SURFACE CHARGE AND WATER TRANSMISSION

The cation‐ and anion exchange characteristics of soils with a large sesquioxide surface area

The mobility of nitrification inhibitors under simulated ruminant urine deposition and rainfall: a comparison between DCD and DMPP

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