Conductometric Titration of Soils for Cation‐Exchange CapacityMortland, M. M.; Mellor, J. L.
doi: 10.2136/sssaj1954.03615995001800040003xpmid: N/A
The reaction of barium‐saturated soil with the sulfate anion of a standardized titrating solution to form insoluble barium sulfate is utilized for determining soil cation‐exchange capacity. The endpoint of the reaction is determined by conductometric titration. Specific conductance remains comparatively constant while the barium on the exchange complex is being titrated. After the barium has been titrated, conductance increases as increments of the titrating solution are added. The endpoint of the reaction is obtained from the intersection of the two linear portions of the curve. Cation‐exchange capacity data obtained by this method are compared with data obtained by other methods on the same soils.
A Comparison of Ammonium Acetate, Barium Acetate, and Buffered Barium Chloride Methods of Determining Cation Exchange CapacityPratt, P. F.; Holowaychuk, N.
doi: 10.2136/sssaj1954.03615995001800040004xpmid: N/A
The cation exchange capacities of several profile samples of soils were determined using three different methods. Total exchangeable cations were determined and used as a criterion for evaluating the different methods of determining the exchange capacity. For all soil samples the NH4OAc method underestimated the exchange capacity and so produced distorted exchange capacity profiles. The Ba(OAc)2 method gave exchange capacity values which were equal to the sum of exchangeable cations, except with highly acid soils where it gave low values. The BaCl2‐buffer exchange capacity gave values that were nearly equal to the sum of the exchangeable cations for all samples tested. The Ba(OAc)2 or BaCl2‐buffer methods, in which Ba is replaced by 0.05 N HCl and the Ba determined using an acetylene flame with a model 52 C Perkin‐Elmer photometer, cannot be used for some samples because of Ca interference. Some slightly acid soils gave sufficient Ca release during the HCl extraction to interfere in the Ba determination. This interference was removed by washing the soil with HCl before leaching with the BaCl2‐buffer and by replacing the barium with NH4OAc.
Surface Accumulations of Nitrates and Other Soluble Salts in California Orange OrchardsHarding, Robert B.
doi: 10.2136/sssaj1954.03615995001800040005xpmid: N/A
Information presented shows that in furrow‐irrigated California orange orchards, as much as 3 tons of soluble salts per acre, representing 800 lbs. of nitrogen as well as other necessary plant nutrients, may accumulate in the upper 6 inches of the interfurrow ridges as a result of capillary conduction. These accumulations have little chance of being of benefit to the trees under present cultural practices. Factors controlling the rate of surface concentration of salts are rate of evaporation, amount of irrigation, kind and amount of soluble salts available as source material, type and shape of furrow, and soil texture and profile characteristics. Surface salt concentrations have been shown to be greater in orchards that are not tilled than in those that are tilled.
The Effect of Sodium Carboxymethylcellulose on Some Physical Properties of Ohio SoilsTaylor, George S.; Baldridge, Paul E.
doi: 10.2136/sssaj1954.03615995001800040008xpmid: N/A
The effect of sodium carboxymethycelluloses (CMC) on soil aggregation, plasticity, moisture equivalent, fifteen‐atmosphere‐percentage, and water permeability was investigated in the laboratory. These compounds contained different degrees of substitution of sodium carboxymethyl groups, ranging from 0.32 to 1.28 substitutions per anhydroglucose unit. In general, increasing the degree of substitution resulted in greater soil aggregation, increased water permeability and larger plastic limits. Varying rates of CMC up to 0.5% concentration also resulted in significant increases in these soil characteristics. None of the compounds had any effect on the moisture equivalent and fifteen‐atmosphere‐percentage. The duration of aggregates stabilized by the 0.70 substitution was found to be much less than those aggregates stabilized by the higher‐substituted types.
The Effect of Some Soil Conditioners on Friability and Compactibility of SoilsJamison, Vernon C.
doi: 10.2136/sssaj1954.03615995001800040010xpmid: N/A
The effect is reported of aggregate stabilization with vinyl acetate maleic acid copolymer upon the breaking strength (Modulus of rupture) of soil briquets molded from several soils of known mineral composition at the moisture content equivalent to the one‐third atm. point of the treated samples. In most cases the stabilization decreased breaking strength, the differences being greatest at the lower bulk densities. Soils rich in montmorillonite gave generally higher Modulus of rupture values than those rich in kaolinite. Aggregate stabilization with this polymer also reduced compressibility of soils with 1:1 lattice type clay dominant, especially at the higher pressures used. The breaking strength of briquets and the water stability of the 1.0 to 0.25 aggregates tests were compared for several materials used to stabilize Lloyd clay aggregates. The various materials affected these two properties differently. A material that increased aggregate stability greatly does not necessarily reduce the briquet breaking strength appreciably. Inter‐aggregate and intra‐aggregate bonding is discussed in light of the results. Field and laboratory tests are reported showing that the method of soil treatment with a stabilizer and weather conditions after treatment will modify the effect upon soil crusts formed. Stabilizers sprayed on the surface may give rise to tough soil‐plastic crusts that are harder than natural crusts upon drying.