Influence of soil specimen preparation and test methods on soil organic matter content

Soil organic matter content (SOM) is used e.g. in soil classification and erosion evaluation. However, its value depends on soil specimen preparation and test method so it is useful to deal with these issues. Totally 150 specimens of soils CI, MS (from Bielsko-Biała, Poland) and different 3 soils, all classified as GC (from Ujsoły, Poland) were tested. To obtain values of SOM, the oxidation method using 30% hydrogen peroxide solution (H2O2) and loss of weight on ignition method (LOI) at 800°C (LOI-800) according to Polish Standard PN-88/B-04481 and LOI at 440°C according to the ASTM D 2974-87 (LOI-440) were applied. The tests were carried out for particles smaller than 0.5 mm. For every soil, 30 specimens (every with a mass about 10 g of dry soil) were prepared from 2400 g of dried soil for 3 methods, so for every method, 10 specimens, taken from various soil amount in frame of total 800 g were prepared. The results showed that values of SOM of tested soils varied from 0.33% to 6.09%. The largest relative difference in values of SOM, caused by soil specimen preparation, was 97.63% (H2O2, soil GC) and the smallest relative difference was 1.65% (LOI-800, soil CI). The largest relative difference in values of SOM, caused by test method was 1126.53% (LOI-800 and H2O2, soil GC) and the smallest relative difference was 15.17% (LOI-800 and H2O2, soil CI). The various values of SOM caused by different test method differently classify soils from organic point of view by the ISO14688-2:2004.

Przeanalizowano wpływ przygotowania próbki gruntu i metody oznaczania na zawartość materii organicznej (SOM). W sumie przebadano 150 próbek gruntów (przygotowanych z różnej ilości gruntu) z Bielska-Białej (CI, MS) oraz z Ujsół (GC). Aby uzyskać wartości SOM zastosowano metodę utleniania 30% roztworem nadtlenku wodoru (H2O2) oraz metodę straty masy przy prażeniu (LOI) w temperaturze 800°C (LOI-800) i 440°C (LOI-440). Badania przeprowadzono dla cząstek gruntu mniejszych niż 0,5 mm. Wartości SOM wahały się od 0,33 do 6,09%. Największa względna różnica wartości SOM spowodowana przygotowaniem próbek wyniosła 97,63% (H2O2, grunt GC), a najmniejsza 1,65% (LOI-800, grunt CI). Największa względna różnica wartości SOM spowodowana metodą badania wyniosła 1126,53% (LOI-800 i H2O2, grunt GC), a najmniejsza 15,17% (LOI-800 i H2O2, grunt CI). Uzyskiwane różne wartości SOM mogą skutkować odmiennym klasyfikowaniem gruntu pod kątem organicznym.