Humus content in soils intended for establishment of permanent plantations in Croatia

Sa？etak Humus has a specific, multiple positive influence on physical, chemical and microbiological soil characteristics. It contributes to the formation of stable aggregates, soil structure and aeration, improvement of infiltration rhythm and to an increase of water storage capacity. Being a storage for plant nutrients, it is a source of fertility at the same time. Furthermore, it is also a buffer against rapid changes in soil reaction (pH) and acts as an energy source for microorganisms in the soil. Taking into consideration aforementioned, as well as the fact that permanent plantations (orchards and vineyards) stay in the same area for a longer time, the need for urgent growth of grass between rows, understanding levels of humus in soils intended for establishment of orchards and vineyards is of utmost importance. Based on the analysis of approximately four thousand soil samples (including topsoil 0-30 cm and subsoil 30-60 cm) from 16 counties in the Republic of Croatia, humus content was determined. Soil samples were taken in the period between 2000 and 2006, in the time of planting major orchards and vineyards, accompanied by incentives for setting us permanent plantations (Bi？ko et al., 2005a; Bi？ko et al. 2005b). Humus content was determined by Tjurin method (？kori？ i Serti？, 1966). Finally, mean values (% humus) of topsoil and subsoil were calculated which accounts for 2.038 samples, representing the same number of plots from which samples were taken. Mean values of humus content per each county ranged between 1.53% in Viroviti？ko-podravska County and 3.32% in Primorsko-goranska County. For other counties the following mean values of humus content were determined: Koprivni？ko-kri？eva？ka 1.54%, Po？e？ko-slavonska 1.62%, Vukovarsko-srijemska 1.63%, Bjelovarsko-bilogorska 1.78%, Brodsko-posavska 1.80%, Zadarska and Me？imurska 2.01%, Sisa？ko-moslava？ka 2.13%, Istarska 2.15%, Zagreba？ka 2.22%, Krapinsko-zagorska 2.23%, Karlova？ka 2.44%, ？ibensko-kninska 2.74% and Li？ko-senjska 2.89%. Identified values were compared with the Report of the European Office for Soil Research (No 15) of the European Commission: “Organic Matter in the Soils of Southern Europe, Zdruli, et al. 2004