Agricultural producers to determine irrigation scheduling practices for crop‘s waterrequirement better when the soil water content of their fields is known. SelyaninovHydrothermal Coefficient (HTC) coefficient is used for identifying droughts duringthe active vegetation period, based on the water balance equation. For farmers tomake measurements of soil moisture is simply with humidity sensors, for exampleWatermark type. Soil humidity values established using Watermark type humiditysensors, value interpretations are based on manufacture indications, however theyhave not been adapted to Lithuanian conditions. Soil moisture was measured withWatermark soil moisture sensors placed at 20 and 50 cm depths. After analysingthe values taken throughout the whole period and summarizing the results it hasbeen identified that plant growth condition period evaluation according to HTC andfactual soil humidity reserves (W) differs by 20%. HTC meaning dependenciesduring vegetation period using Watermark measured humidity, strong or averagelystrong interrelation is determinate, in most cases – statistically significant. Whenevaluating soil humidity reserves based on soil texture, it is recommended to keepthe critical Watermark level in light texture soil (sands) at 80 cbar, and in all othertypes of soil - at 150 cbar. The results clearly indicate that soil composition couldbe factors limiting the success of identifying droughts in agriculture carried byWatermark type humidity sensors.

This study provides the analysis of drought conditions of vegetation period in 1982-2014 year in two Lithuanian regions: Kaunas and Telšiai. To identify drought conditions the Standardized Precipitation Index (SPI) was applied. SPI was calculated using the long-term precipitation record of 1982–2014 with in-situ meteorological data. Calculation step of SPI was taken 1 month considering only vegetation period (May, June, July, August, September). The purpose of investigation was to evaluate the humidity/aridity of vegetation period and find out the probability of droughts occurrence under Lithuanian climatic conditions. It was found out that according SPI results droughts occurred in 14.5 % of all months in Kaunas region and in 15.8 % in Telšiai region. Wet periods in Kaunas region occurred in 15.8 %, and in Telšiai region occurrence of wet periods was – 18.8 % from all evaluated months. According SPI evaluation near normal were 69.7 % of total months during period of investigation in Kaunas and respectively – 65.5 % in Telšiai. The probability for extremely dry period under Lithuania climatic conditions are pretty low – 3.0 % in middle Lithuania and 2.4 % in western part of Lithuania.