Sequential Micronutrients Extraction from Toposequences of Pasture Soils

Abstract

The objective of this study was to determine changes in soil properties and micronutrient content (Fe, Cu, Mn and Zn) development along a slope in pasture soils. The study area is located in Kocadag, Samsun, Turkey. Three landscape positions i.e., summit, backslope and footslope, were selected. Soil samples for all genetic horizons were taken from all landscape positions of pasture. Some physico-chemical properties such as organic matter content, pH, CaCO₃, exchangeable cations and sequential micronutrient fractions (exchangeable, organically complexed, manganese oxide bounded, amorphous and crystalline iron oxide bounded and residual) were determined. All micronutrient pools, horizons were affected by slope position. The micronutrient fractions and particularly the exchangeable (EX-), organically complexed (OM-) fractions tended to decline with soil dept. The residual fraction (R-) was proportionally the largest fraction and EX- and OM- fraction were the smallest fractions at all horizon and landscape position. In footslope position, the soils had generally the higher total micronutrient contents and their R- fractions than the other positions at all genetic horizons. In all positions, except for R- fraction, micronutrient fractions in soils decreased from the surface downward indicating that the major part of the location is existed to the A horizon.