Spatial Heterogeneity of Soil Silicon in Ukrainian Phaozems and Chernozems

Abstract

This study investigated the spatial variability of the soil silicon content in relation with topography, parent materials, soil texture, soil organic matter, exchangeable cations and pH. Using the experimental data from two longterm sites in the Forest-Steppe area of Ukraine, the SiO2 content was estimated in 60 samples taken from a soil depth 0-25 cm. The accumulation of SiO2 was significantly greater in the soils formed in footslopes. A content of extractable silicon fraction significantly increased from a sandy loam- (366-465 mg•kg-1) to medium- (670-697 mg•kg-1) and heavy- (506-849 mg•kg-1) textured soils. The highest amount of available silicon content was found in the soils containing: 35.0-39.9% of physical clay fraction (< 0.01-mm dia) in Hrytsiv area – 143.0 ± 46 mg•kg-1 and < 25.0% of physical clay fraction in Khrolyn area – 125.0 ±6 mg•kg-1. A significant relationship was found between pHKCl, P2O5, K2O, Mg and both forms of SiO2. There was almost no correlation between available/ extractable SiO2 and exchangeable Ca and ∑ Ca+Mg. Our studies found the best correlation between extractable SiO2 and spring barley yield (r = 0.651; P = 0.041), as well as soluble SiO2 and corn for grain yield (r = 0.514; P = 0.128). No significant relationships were found for sugar beet, winter wheat, sunflower. This fact can be explained by the significant influence of other factors on crop yields, such as: fertilizing system, soil organic matter content, available moisture content, major nutrients content in soil, etc.

Keywords

• ph
• fertilization
• silicon
• soil texture
• chernozem
• exchangeable cations