Measurements of Texture of Soils Formed from Glaciolimnic Sediments by Areometric Method, Pipette Method and Laser Diffraction Method
Abstract The aim of the research was to compare the results of texture analyses of glaciolimnic sediments deposited in the basins of ice-dammed lakes origin in north eastern Poland. The study was carried out using aerometric method, pipette method and laser diffraction method. The studied soils were classified as Haplic and Mollic Vertisol, Vertic Cambisol, and Gleyic Chernozem. The soils were formed from clayey (clay, heavy clay), loamy (loam, clay loam, sand clay loam) and silty (silt loam, clay loam) deposits. The studied soils did not contain fractions > 2.0 mm. The amounts of clay fraction (< 0.002 mm) measured by areometric and pipette methods were similar and strongly correlated. In comparison to laser diffraction method, these amounts were 3-4-fold higher. The sub-fraction of fine silt (0.02-0.002 mm) predominated in soil formations analyzed by laser diffraction method. In comparison to areometric or pipette method, the amounts of fine silt were 2-4 fold higher. Basing on the calculated sedimentological indices, it was stated that the examined soils were well sorted and the mean grain diameter (GSS) was very low and did not exceed 0.005 mm in areometric and pipette methods, and 0.011 mm in laser diffraction method for clay sediments.
Methodological aspects of determining soil particle-size distribution using the laser diffraction method.
This paper presents the influence of selected methodological aspects on the results of particlesize distribution (PSD) as measured by the laser diffraction method (LDM). The investigations were carried out using the Mastersizer 2000 with Hydro MU attachment (Malvern Ltd., UK). It was found that for the investigated soils: (1) optimal speed of pump and stirrer was 2500 rpm, (2) optimal measurement time was ≈ 1 min, (3) there are two, practically equivalent methods for soil-sample dispersion: chemical (with the use of a solution of sodium hexametaphosphate) or physical (by means of ultrasound application for 4 min at a maximum power of 35W), (4) one must not use the chemical and physical dispersing methods simultaneously, because this can lead to aggregation (not dispersion) of soil particles, (5) the Fraunhofer theory (physical models) can be used to convert scattered-light data to PSD. In the case of the Mie theory, the best results were obtained for a refractive index (RI) in the range of 1.5–1.6 and an absorption index (AI) of 1.0. It was also found that most of the discussed parameters depend on design of the measuring device and on the type and volume of the investigated suspensions. It is necessary, therefore, to explain how the data was obtained every time and to specify the details in the methodological part of the paper.
Effect of forage cropping treatments on soil structure and relationships with fractal dimensions
Abstract Effects of six different forage cropping treatments, perennial ryegrass (RG), alfalfa (AL), bromegrass (BR), small burnet (SB), subterranean clover (SC) and purple crownvetch (CV), on soil structural parameters such as, mean weight diameter (MWD), aggregate stability (AS), dispersion ratio (DR), bulk density (BD) and penetration resistance (PNTR) were determined. Forage cropping decreased the proportion of microaggregates in the fractions  1.00 mm in size. All forage cropping significantly increased organic carbon (OC) content (1.34–1.84%), MWD (0.89–1.15 mm), AS (71.76– 80.01%) and decreased DR (15.30– 9.76%), BD (1.45–1.28 g cm − 3 ) and PNTR (2.94– 1.89 MPa) compared with the fallow control treatment. The most positive effects on soil structural parameters were generally obtained with BR treatment while the lowest effects on that were obtained with RG treatment amongst the forages. Fragmentation ( D ) and mass ( D m ) fractal dimensions were decreased with increasing numbers of macroaggregates of the clay soil due to forage cropping. The lowest values of D and D m were found as 2.059 and 1.582 for BR treatment while the highest values of them were found as 2.683 and 2.085 for the control treatment, respectively. Both fractal dimensions gave positive relationships with OC content, MWD, AS, and negative relationships with DR, BD and PNTR. Development of macroaggregates in clay soil by the forage cropping was represented by the fractal dimension better than mass fractal dimension and MWD.