SPATIAL VARIATION OF PHYSICAL CLAY AND ORGANIC CARBON IN THE COMPLEX OF CINNAMON FOREST SOILS (CHROMIC LUVISOLS) AND THEIR SUITABILITY FOR CULTIVATION OF VINES Krasimir TRENDAFILOV, Violeta VALCHEVA Agriculture University, 12 Mendeleev Blvd., 4000, Plovdiv, Bulgaria Corresponding author email: trendafilovk@mail.bg Abstract Object of this study are lands in the village Balabanchevo, municipality Sungurlare, Bulgaria. The main soil type in the region is Chromic luvisols with soil profile differentiated to different degree. In the current work is studied the spatial variation of soil organic matter and physical clay content, depending on the topographical location and the degree of erosion. Studied soils are characterized by two main processes that determine the their particle size distribution - lessivage, causing accumulation of clay in subsoil and surface erosion, which is responsible for removal of relatively sandy upper layers and remaining of clayey subsurface horizons on the top. In this research is determined particle size distribution in three depths - 0-25, 25-50 and 50-75 cm and the content organic carbon in the surface horizons. Differences in clay content determined in the three studied depths are substantial and statistically significant. Differences between sampling points in respect toorganic matter content are insignificant. Relatively high levels of humus content is detected only in a small part of investigated area, where are distributed relatively dark colored soils with expressed meadow soil formation process, and in the northern and the southern parts, where to some extent more strongly is retained humus formation effect of the natural vegetation. Key words: Chromic luvisols, geospatialization, organic carbon, physical clay. INTRODUCTION In topsoil, the ideal soil structure is formed by predominantly crub-like aggregates, best formed when organic matter is naturally high (> 2% organic carbon content) and well humified (Greenland et al. 1975). The role of organic matter is less significant in the subsoil where the soil texture and the exchangeable cations are more important (Bronick and Lal, 2005). Soils rich in organic matter are generally high in available nutrients. Soil texture is an important consideration in variety and rootstock selection due to its effect on vine growth and potential nematode and/ or phylloxera damage. Soil texture largely influences vine growth due to its effects on water holding capacity and nutrient availability. Generally, finer-textured soils have a higher water holding capacity and higher native fertility thereby producing vines of higher growth potential as compared to sandy soils (McKenry and Christensen, 1998). Clay soils can fix potassium in soil, thereby decreasing the availability of this nutrient to the plant. Particle size distribution however is an absolute limitation when the content of physical clay is less than 10% or more than 70%. Present study is a part of soil amelioration survey of derelicted, because of their low natural fertility terrains in the hilly Central Eastern part of Bulgaria. The task we set ourselves is to be defined the boundaries of soil heterogeneity in relation to organic carbon content and particle size distribution of soil. MATERIALS AND METHODS During the current research we accepted a model for collecting of soil samples in which each sample is taken from the terrain with soil probe as the sampling points are situated in square grid, regardless of the borders of soil types and local terrain topography. We studied two sections-parcels 108 and 155 (Figure 1), which have complex topography and parcels 113, 157 and 158 (Figure 2), where the terrain is relatively leveled and with slightly rough and monotonous relief. Parcels 108 and 151, and 140 Scientific Papers. Series A. Agronomy, Vol. LVI, 2013 ISSN 2285-5785; ISSN CD-ROM 2285-5793; ISSN Online 2285-5807; ISSN-L 2285-5785