Potassium as an indicator of soil profile formation and change of its physico-chemical properties

Abstract

Taking into account the importance of potassium for soil diagnostic puiposes, the investigations on the formation peculiarities of the youngest (Northern Lithuania) and the oldest (Eastern Lithuania) loamy soils were carried out in 2016-2017. Having made a soil profile description, the allocation of each investigated soil was done according to the WRB classification system (2014 edition). Soil samples for physico-chemical analysis were collected from the genetic horizons of the soil profiles. Undisturbed core samples for determining bulk density of soil and total porosity were collected using stainless steel rings (100 cm3 volumes) in four replications. Bulk density and total porosity were calculated from undisturbed soil samples. For chemical analyses, the soil samples were air-dried, crushed and sieved through a 2-mm sieve and homogeneously mixed. The data obtained shows that total potassium content has a direct strong correlation (r = 0.83 in Luvisol and r = 0.83-0.98 in Planosol) with soil clay and silt fractions content, thus, indicating a direct relationship between these soil constituents. However, this relationship remains statistically significant only in subsoil whose formation is not affected by SOC. The distribution of mobile K in studied soil profiles is related to the distribution of soil organic material and its migration throughout the soil profile. The correlation of total and mobile K with SOC can be estimated only by analysing the distribution of potassium in the humic soil horizons. The negative correlation (r = -0.97) indicates that the soil is not affected by the agricultural activity. The positive strong correlation (r = 0.99) shows a direct or indirect effect of adjacent agricultural areas and potassium soiption in soil organic matter. The correlation between soil bulk density ant total porosity it was estimated a little bit lower in the Planosol compared to the Luvisol.