TEMPERATURE AND MOISTURE REGIMES OF RENDZINA SOILS IN SERBIA ACCORDING TO THE USDA SOIL TAXONOMY SYSTEM

Abstract

Soil moisture and temperature regimes are diagnostic characteristics used for higher categories of the USDA Soil Taxonomy System. The first step of Rendzina soil classification in Serbia according to this international system is to determine the soil temperature and moisture regime classes. As measured soil moisture and temperature data of the investigated Rendzina profiles were missing, the Rendzina soil temperature and moisture regimes were estimated based on climate data (30 years) – monthly and annual air temperature and precipitation, and potential evapotranspiration. Six weather stations were selected: at Novi Sad for the northern, Valjevo for the western, Belgrade for the central, Negotin for the eastern, Sjenica for the southwestern and Niš for the southeastern regions of Serbia. The estimated mean annual soil temperature in the study areas ranged from 8.7 to 14.5°C, and the mean summer and winter soil temperatures differed by 18.6-21.4°C. The Rendzina soils in all the study areas match the criteria for the mesic soil temperature regime. Precipitation becomes greater than potential evapotranspiration and water recharge begins in September in Sjenica and October in the other areas. Potential evapotranspiration exceeds precipitation and utilization starts in March (Novi Sad, Belgrade and Niš) or April (Valjevo, Sjenica and Niš). The amount of moisture stored in the soil during this period, plus precipitation, is believed to be sufficient to support potential evapotranspiration and avoid significant water deficits in western and southwestern Serbia (Valjevo and Sjenica). Utilization is expected to exceed recharge plus precipitation in all other areas, causing soil water deficit to begin in April in Belgrade and May in Novi Sad, Negotin and Niš. Therefore, the soils in the western and southwestern areas match the criteria for the udic soil moisture regime, whereas soils in the other areas (central, east and southeast) correspond to the ustic soil moisture regime. Possibly lower water infiltration and available water capacity, caused by geomorphological and physical properties of Rendzina soils, can increase water deficits further, but precipitation in the summer months is hopefully sufficient to avoid long periods of dry days. Separation of Rendzina soils in Serbia into two soil moisture regimes, udic and ustic, could affect their classification at higher taxonomic levels according to the Soil Taxonomy System.