The evaluation of the humidity of vegetation period

The fertility of agricultural vegetation basically depends on the terms and hydrologic conditions of vegetation period. These conditions are determined by warmth and precipitation and its distribution. This article analyzes the methods of the evaluation of these conditions in the period of active vegetation (in May-September). The calculations received applying these methods are presented and the differences between the last 60-80 vegetation periods are shown. In order to define the differences between the indirect methods of humidity evaluation, the methods used in Lithuania -G.Selyaninov's hydrothermal coefficient (HTC) and A. Dirse's coefficient of complex humidity (AT), which evaluates the resources of the soil moisture -are analyzed and compared. It is noticed that the humidity, evaluated applying HTC and K, is different. The periods in January, evaluated applying HTC, make 18% and, evaluated applying the complex coefficient K, make 27% of the total investigated period, or accordingly - 28% and 15% characterizing the period of one month. According to the results of the analysis, it is stated that the complex cocfTicient K is more precise in evaluating the period of humidity in the climatic Lithuanian conditions. In addition, it is suggested to specify the methodology of the evaluation of ihc humidity of vegetation periods, relating the applied K and HTC coefficients with the actual soil moisture contentVytauto Didžiojo universitetasŽemės ūkio akademij