Recommendations for agricultural drought assessment under Lithuanian climatic conditions

Among the environmental stresses, drought stress is one of the most adverse factors that negatively impacts plant growth and productivity. Therefore, understanding and qualifying drought occurrence and its consequences on agricultural production, hydrologic cycle, and ecosystems is of particular importance. In the context of climate variability and change, water scarcity and food security, it is important to use more comprehensive data on rainfall, temperature and soils in computing drought indices. Currently for drought monitoring different indices, easily understandable, are used by end users. The Standardized Precipitation Index (SPI) was proposed by McKee et al. (1993) and it has been increasingly used during the last decades because of its solid theoretical development, robustness and versatility in drought analyses. Nevertheless for many years, the humidity of vegetation period has been described using Selyaninov's hydrothermal coefficient (HTK) in Lithuania. According to Farrago's classification, it belongs to drought indices of water balance group "supply/demand" as it uses daily values of precipitation and air temperature for the calculation of the period. Anyway drought affects water availability not only by changing regional precipitation level and temporal variability, but also by affecting water flows and soil moisture dynamics. Therefore it is essential lo have soil moisture data as one of the most important factors for evaluation of drought occurrence. Finally when all meteorological data are observed and soil moisture is monitored it is very important lo know what stress reaction of plants is. Results of investigation revealed a very strong negative relationship between soil moisture water content and proline content as well as between soil moisture water content and soluble sugar content in leavesVytauto Didžiojo universitetasŽemės ūkio akademij