The aim of this paper was to show how the shape of sand particles affects the results of particle size distribution obtained by the laser diffraction method. On the basis of the results obtained one can conclude: the shape of the investigated particles influences particle size distribution obtained by the laser diffraction method. This phenomenon occurs in the sand fraction, as shown in our investigation. The importance of this effect depends on the type of the measured material and on the aim of the investigations. For most researchers in soil science and sedimentology who investigate sand fractions, this impact can be negligible. Further investigations with other soil and sediment fractions are needed.

Particle size distribution is an important soil parameter—therefore precise measurement of this characteristic is essential. The application of the widely used laser diffraction method for soil analysis continues to be a subject of debate. The precision of this method, proven on homogeneous samples, has been implicitly extended to soil analyses, but this has not been sufficiently well confirmed in the literature thus far. The aim of this study is to supplement the information available on the precision of the method in terms of reproducibility of soil measurement and whether the reproducibility of soil measurement is characterized by a normal distribution. To estimate the reproducibility of the laser diffraction method, thirteen various soil samples were characterized, and results were analysed statistically. The coefficient of variation acquired was lowest (3.44%) for silt and highest for sand (23.28%). Five of the thirteen tested samples were characterized by a normal distribution. The fraction content of eight samples was not characterized by normal distribution, but the extent of this phenomenon varied between soils. Although the laser diffraction method is repeatable, the measurement of soil particle size distribution can have limited reproducibility. The main cause seems to be small amounts of sand particles. The error can be amplified by the construction of the dispersion unit. Non-parametric statistical tests should be used by default for soil laser diffraction method analysis.

One of the methods for testing splash (the first phase of water erosion) may be an analysis of photos taken using so-called high-speed cameras. The aim of this study was to determine the reproducibility of measurements using a single drop splash of simulated precipitation. The height from which the drops fell resulted in a splash of 1.5 m. Tests were carried out using two types of soil: Eutric Cambisol (loamy silt) and Orthic Luvisol (sandy loam); three initial pressure heads were applied equal to 16 kPa, 3.1 kPa, and 0.1 kPa. Images for one, five, and 10 drops were recorded at a rate of 2000 frames per second. It was found that (i) the dispersion of soil caused by the striking of the 1st drop was significantly different from the splash impact caused by subsequent drops; (ii) with every drop, the splash phenomenon proceeded more reproducibly, that is, the number of particles of soil and/or water that splashed were increasingly close to each other; (iii) the number of particles that were detached during the splash were strongly correlated with its surface area; and (iv) the higher the water film was on the surface the smaller the width of the crown was.