Regime of Soil Temperature During the Sowing Period of Spring Crops in the Some Stations of South-Eastern Bulgaria

Object of this study is the regime of soil surface temperatures down to 20 cm depth during the period of sowing and initializing stages of spring crops development. The area to the west of Burgas is on the border of the Black Sea sub region of the Continental-Mediterranean region. The annual course of rainfall is characterized by maximum during November and minimum in August. Less pronounced is the continental influence with a secondary maximum in June. The area is generally classified as dry but mitigated compared to the interior of southern Bulgaria and with higher relative air humidity. In terms of temperature conditions, the spring is a cooler and the sharp decreases are lower. The аgro-ecological resources of the region during the last 30 years have defined it as dry, moderately hot. Increasing tendencies last 30 years in air temperature have been established compared to 1961-1990. In recent years, scientists have focused their research mainly on air temperature. It is known that soil temperature is very important, and in the initial stages-the main for development of spring cultures. Are there any trends in the climatic conditions of the depth of sowing of spring cultures (above the surface of the soil, 0.00 m, 0.02 m, 0.05 m, 0.10 m and 0.20 m) is also an issue of scientific interest? The aim of the research is to study the regime of the soil temperature during the spring months in relation to the precision of sowing and the start and development of some spring crops grown in the South-Eastern Bulgaria.