Seasonal temperature dynamics in the profile of leached chernozem under iris plantations

Abstract

Throughout the annual cycle, each individual iris plant develops through the stages as foliage growth, budding and flowering. The duration of iris flowering is mainly affected by air temperatures and soil moisture content during budding. Under favorable conditions, the flowering may last up to 22 days. But in dry and hot weather this period is shortened. On October 20, due to the warm autumn, the chernozem profile under the iris plantations turned out to be well warmed up. As a result of the cold snap at the end of the month, the soil temperature dropped quickly. In the third ten-days of November, the freezing began, and positive temperatures were observed from a depth of 25 cm. The accumulated temperature decreased. The heat flow on October 20 turned out to be zero which indicated the termination of heat flow into the soil. The presence of formed snow cover in December reduced the rate of cold entry into the lower horizons of the soil which temperature did not fall below 1.5°C for three months. At a depth of 25 cm it varied within insignificant limits. Negative temperatures penetrated to a depth of 50 cm only in the third ten-days of February. The temperature profile in the soil from the beginning of March until mid-April remained in a stationary state, keeping the temperature equal to zero down to a depth of 50 cm. The accumulated temperature and heat flow also did not change. In the third ten-days of April, the snow melted and the soil began to warm up intensively. The temperature here during May rose to 21°C. The accumulated temperature increased accordingly. The heat flow in the 0-25 cm layer at the end of April to the beginning of May reached 20 W m², and then it decreased to zero.