Nowadays there is a growing demand for rapid and accurate determination of grain size distribution. The conventional pipette method is time-consuming and provides less detailed data compared to recently introduced methods. However, in Hungarian practice the pipette method is still considered to be the standard one, as there are a long series of measurements, and grain size thresholds used in sedimentology and soil sciences are based on this approach. The aim of our research was to determine the comparability of the laser diffraction method (LDM) with the conventional pipette method (PM), in order to investigate the controversial question on the interchangeability of the two methods. Based on our measurements on some representative fluvial sediment samples, we found that the largest difference in results can be expected in the silty grain size range. However if the main fractions (clay, silt, sand) are considered the methods provided similar very results, and correlation factors were above 0.92. In all, the LDM has a clear advantage because of its speed, reproducibility and fewer possibilities for operator failure.

Particle size distribution is one of the most influential factors of most soil physical and even some soil chemical characteristics. As modern measurement techniques are being introduced, the need for comparing new methods with older methodologies arises because comparability means data continuity. Here, three institutes conducted a comparison of particle size measurement among the laser, areometer and pipette techniques. The purpose of the comparison was to a) discover any differences among operators, laboratories, and techniques; b) identify if there were any differences and if they could be linked to soil type (e.g. high clay, loam, or sand content) or particle size range; and c) understand if the laser diffraction method gave results that were significantly larger than the other methods of any size fraction. There was no statistically proven difference between the two operators examined based on the pipette method's result. The comparison of two of the institutes' pipette methods showed statistically significant differences for three of the eight samples tested. However, these differences only seemed to appear in the 0.01 mm to 0.02 mm particle size range. A technical comparison among all three methods resulted in significant differences in all cases except for one sample that had very high sand content and very low clay content. Finally, the laser diffraction method was analyzed to see if it measured a larger amount of the clay fraction, however, it instead overestimated the silt and the fine sand (0.01 mm to 0.02 mm) fraction, not the clay fraction. Therefore, we conclude that different methodologies can provide significant difference in particle-size measurement. Based on the results, we recommend creating a widely accepted patent for sample preparation (disaggregation, the use of peroxide or other agents, using ultrasonic or other methods) and for measuring techniques (a set of refractive and sorption indexes, using ultrasonic during the measurement, pump speed etc.).

A useful method to evaluate the effectiveness of soil-erosion models is to compare the models' soil-loss and runoff calculations with measured data from experimental plots subjected to artificial rainfall. This study was conducted to develop a set of statistics to compare the performance of the soil-erosion models EUROSEM, WEPP, and MEDRUSH. Rainfall (six rainfall intensities, two replicates), runoff, and soil-loss data from artificial plots at two locations in Hungary were used to assess the accuracy of the different models. The soil types within the plots represented a wide range of soil properties and are soil types that are commonly used for agriculture. The results showed that the three soil-erosion models performed with varying effectiveness dependent on basic soil properties. However, statistical analysis showed the EUROSEM model to be the best for estimating soil loss in Hungary.

In this study we focused on the factors aff ecting fi nal outputs of the USLE (Universal Soil Loss Equation) model. In doing so, we conducted soil particle size measurements in diff erent institutions (University of Debrecen, University of Szeged and Geographical Institute, Research Centre for Astronomy and Earth Sciences of the Hungarian Academy of Sciences) with a variety of methodologies (laser, aerometer and pipett e methods) on various soil materials (sandy, loamy and clay). Statistical analyses of the eight examined soil samples have been shown some signifi cant and some non-signifi cant diff erences among the particle size measurements. This paper is aimed at i) to ascertain whether these signifi cant diff erences in particle size measurements cause signifi cant diff erences in soil erodibility calculations; and ii) to assess the amount of soil loss calculated by these K factors. The results suggest that regardless of the relatively small percentage between the smallest and the greatest K factor values, the amount of soil loss can be fairly high, especially when erosion occurs on a longer or steeper slope. In the present case, when we compare simulations results, the amount of soil loss is more important than the diff erence in percentage between the minimum and maximum values. Because the percentage of the diff erence can remain the same between the simulations, while the amount of soil loss increases way beyond soil loss tolerance limits.

No abstract