Assessment of agronomic drought occurrence and severity in agricultural regions of Slovakia is presented in the paper. Drought severity assessment is based on the soil water dynamics simulation by agroecological model Daisy. Daily meteorological data from the years 1961-2012 from 31 localities were used in simulations. Criteria for the drought occurrence were 1) available soil water content below 50% of available water capacity, 2) soil water content below long-term average soil water content and 3) duration of continuous drought for fifteen or more days. Standardized index of daily available soil water content was used for drought severity classification. According to the index the drought is categorized into four degrees of severity from mild to extreme drought. Cumulative sum of available soil water index was used to drought quantification throughout its duration. Normal climate period 1961- 1990 was chosen as reference period to enable historical comparison of drought severity as well as climate change impacts. Extreme drought of the largest spatial extent was identified in 1990. Extreme drought occurred regionally in the southwest Slovakia in 1978 and in the southeast Slovakia in 1986, respectively.
Evaluation of Adaptive Measures to Reduce Climate Change Impact on Soil Organic Carbon Stock In Žitný Ostrov Region
Climate change impacts on soil organic carbon sequestration rate were simulated by agroecological model DAISY. Daily meteorological data for the Danubian Lowland up to 2100 were generated according to emission scenarios SRES A2 and B1 using general circulation model CGCM3.1. Effect of gradual increase of CO2 concentration in the atmosphere was taken into account. Various crop rotations as well as various management practices including irrigation and crop residuals incorporation were considered in three variants: i/ rainfed, residuals not incorporated, ii/ irrigated, residuals not incorporated, iii/ summer crops irrigated and residuals incorporated. Modelling outputs confirm that conventional rainfed agro-technical practices without incorporation of crop residues resulted to significant loss of soil organic carbon in soil profile towards more distanced time slices. The irrigation and the incorporation of crop residuals including stems and leaves can reduce soil organic carbon losses. If it is combined with proper crop rotation the soil organic carbon stock in soil profile can even increase.
Soil organic carbon (SOC) in agricultural land forms part of the global terrestrial carbon cycle and it affects atmospheric carbon dioxide balance. SOC is sensitive to local agricultural management practices that sum up into regional SOC storage dynamics. Understanding regional carbon emission and sequestration trends is, therefore, important in formulating and implementing climate change adaptation and mitigation policies. In this study, the estimation of SOC stock and regional storage dynamics in the Ondavská Vrchovina region (North-Eastern Slovakia) cropland and grassland topsoil between 1970 and 2013 was performed with the RothC model and gridded spatial data on weather, initial SOC stock and historical land cover and land use changes. Initial SOC stock in the 0.3-m topsoil layer was estimated at 38.4 t ha−1 in 1970. The 2013 simulated value was 49.2 t ha−1, and the 1993–2013 simulated SOC stock values were within the measured data range. The total SOC storage in the study area, cropland and grassland areas, was 4.21 Mt in 1970 and 5.16 Mt in 2013, and this 0.95 Mt net SOC gain was attributed to inter-conversions of cropland and grassland areas between 1970 and 2013, which caused different organic carbon inputs to the soil during the simulation period with a strong effect on SOC stock temporal dynamics.