| dc.description.abstract | Soil structure pertains to the natural organization of soil particles into various forms as a result of pedogenic processes. On one hand, it is formed in interaction of physical, chemical, mineralogical, and biological factors, whereas on the other hand it affects them. Soil structure can differ in grade of development, size and type of aggregates, and their stability to mechanical pressure and water, which is often soil-horizon or soil-type dependent. This paper aims to analyze the structure of Calcomelanosols of mountain Rtanj, Serbia, as that is the most widespread soil type in this area. Calcomelanosols are soils from the national classification system that often correspond to Rendzic Leptosols in the World Reference Base (WRB) for soil resources. Soil structure is analyzed in terms of soil dry aggregate size distribution (ASD) and soil aggregate stability to water (WAS), and related soil structure indices, as they are essential parameters in understanding the structural state of the soil. Eight soil profiles have been excavated, described and sampled in the field. Soil horizon sequence of all profiles was A – R, with humus-accumulative horizon overlying calcareous bedrock. Six profiles of Calcomelanosols correspond to Rendzic Leptosols of WRB, whereas other two profiles correspond to Leptic Rendzic Phaeozems and Leptic Chernic Rendzic Phaeozems. Basic physical and chemical soil properties were determined. Both ASD and WAS were determined by Savinov's method. The following soil structure indices were calculated: dry mean weight diameter (dMWD), wet mean weight diameter (wMWD), dry geometric mean diameter (dGMD), wet geometric mean diameter (wGMD) and structural stability index (SI). The results indicate favorable structure of the examined Calcomelanosols. The content of agronomically most valuable aggregates (0.25–10 mm) in all soil profiles exceeds 80% (90.5±3.6% on average). Among these aggregates, very fine, fine and medium size aggregates dominate. Dry MWD showed values ranging from 3.0–5.5 mm, whereas wMWD ranges from 1.9– 3.3 mm. The wMWD and dMWD ratio is an indicator of the stability of structural aggregates. A small change in the aggregate size after wet sieving was found, 0.7±0.1 mm on average. In all examined soil profiles SI is higher than 19% (32.9±7.1% on average), which indicates an extremely stable structure, without risk of the structural degradation of soil. Correlation analysis showed a significant positive relationship between the content of agronomically valuable fractions (0.25–10 mm) and the following soil parameters: soil organic matter (SOM), pH, and base saturation (%V). Also, there is a strong positive correlation between SI and pH, and SI with %V. Other calculated structural indices show a strong negative correlation with SOM, pH and %V. All analyzed soil profiles have favorable soil structure and water stable soil aggregates with low risk of soil structure degradation. This is of extreme importance because Calcomelanosols cover the steep and
sloping land which is naturally more prone to soil water erosion and soil degradation. | sr |
