Comparasion of methods of determining the mechanical composition of soil

Mehanički sastav tla vrlo je važna fizikalna značajka tla. O njemu ovise brojne druge fizikalne (struktura, vodozračni odnosi, propusnost tla za vodu, zbijenost), kemijske (pH, oksidacija i redukcija, adsorpcijski kompleks tla) i biološke značajke (bioraznolikost, brojnost i zastupljenost pojedinih skupina živih organizama). Mehanički sastav tla pokazuje postotnu zastupljenost pojedinih mehaničkih elemenata u tlu (pijeska, praha i gline), a može se utvrditi različitim metodama. Cilj rada je utvrditi postoje li razlike u rezultatima analize mehaničkog sastav između tri metode: klasične pipet metode (koja se godinama koristi i priznata je u svijetu kao standardna metoda za pedološka istraživanja), te areometriranja i laserske difrakcije (metode koje se više koriste u geološkim istraživanjima). Analizirano je 20 uzoraka različitog mehaničkog sastava. Dobiveni rezultati analize obrađeni su u MS Excel-u (minimalna, maksimalna i prosječna vrijednost), dok je statistička obrada provedena t-test-om uz Bonferroni-jevu korekciju korištenjem programskog paketa SAS. Analizom je utvrđeno da postoje statistički značajne razlike u rezultatima između pojedinih metoda određivanja kod analiziranih frakcija (pijesak, prah i glina), s tim da se rezultati postotnog udjela frakcija gline statistički značajno razlikuju u svim trima korištenim metodama. Dok se rezultati areometriranja više poklapaju sa rezultatima klasične pipet metode za pjeskovitu frakciju, laserska difrakcija pokazuje bolje poklapanje sa klasičnom pipet metodom za frakciju praha. Usporedbom rezultata interpretacije teksturne oznake uočeno je značajno odstupanje areometriranja u odnosu na ostale dvije metode. Klasična pipet metoda i laserska difrakcija imaju 45% analiziranih uzoraka u istoj teksturnoj klasi.The mechanical composition of the soil is a very important physical feature of the soil. It is dependent on numerous other physical (structure, water-air relations, soil permeability to water, compaction), chemical (pH, oxidation and reduction, soil adsorption complex) and biological characteristics (biodiversity, number and representation of particular groups of living organisms). The mechanical composition of the soil shows the percentage representation of certain particles of the soil (sand, slit and clay), and can be determined by different methods. The aim of this study is to determine whether there are differences in the mechanical composition analysis between three methods: the classical pipette method (used for years and recognized worldwide as a standard method for pedological research), and areometrics and laser diffraction (methods used more in geological research). Twenty samples of different mechanical composition were analyzed. The obtained analysis results were processed in MS Excel (minimum, maximum and average value), while statistical processing was performed by t-test with Bonferroni correction using the SAS software package. The analysis found that there were statistically significant differences in the results between the different determination methods for the analyzed fractions (sand, silt and clay), with the results that the percentages of the clay fractions were statistically significantly different in all three methods used. While the areometric results are more in line with the results of the classical pipet method for the sand fraction, laser diffraction shows a better match with the classical pipet method for the powder fraction. Comparison of the texture characteristic interpretation results showed a significant deviation of areometrics with respect to the other two methods. The classical pipette method and laser diffraction have 45% of the analyzed samples in the same texture class