Comparison of Standardized Precipitation Index (SPI) and Standardized Potential Evapotranspiration Index (SPEI) applicability for drought assessment during the maize growing period between Bărăgan (Romania) and Prekmurje (Slovenia) regions (1991-2020)

In recent years, drought has become an increasing problem in agricultural production in many places where these problems did not exist in the past. The frequency and intensity of agricultural droughts are increasing, so it is very important to detect temporal and spatial variability of drought. This study analyzed the properties of agricultural drought (duration and intensity) in Bărăgan region (Romania) and Prekmurje region (Slovenia) between 1991-2020 based on the Standardized Precipitation Index (SPI) and the Standardized Precipitation Evapotranspiration Index (SPEI) at different time scales. The reasons for comparing the two regions are similar climatic conditions, the importance of maize cultivation for food security, and repeated droughts in the recent period in these regions. The meteorological data for Romania were provided from ROCADA database, and for Slovenia from SLOCLIM database. Furthermore, relationships between drought-sensitive phenological stages of maize (germination, formation of the first 2 leaves, and flowering), growing season length, thermal time above threshold 10 °C, standardized yields, and calculated drought indicators were calculated. Based on our analysis, we expect to be able to evaluate whether SPI and SPEI can be used to monitor conditions on a variety of time scales and to provide indicators at regional scales on the likely occurrence of drought during critical phenological phases of maize, as well as the differences and similarities between the two regions will be discussed.