SEASONAL FEATURES OF HEAT AND MOISTURE CONTENT IN THE SOIL PROFILE WHEN IRRIGATING MOUNTAIN ASH PLANTATIONS IN THE ARBORETUM
The summer season of 2018 was quite warm. Under the influence of high temperatures (up to 35°C) in July, the average daily accumulated temperatures in the root layer turned out to be the maximum and amounted to 98.8°C. Thus, the heat content reached 37% on this month, and in June and August it did not exceed 32% and 30%, respectively. The winter season of 2018-2019 was “soft” which led to a slight freezing of the soil layer. In total, the summer of 2019 turned out to be cool. The temperature reached its maximum only in August. The total and available moisture levels in June of 2018 in the humus-accumulative horizons A and AB decreased to a critical value when the moisture content dropped to the wilting moisture content. The weather conditions in July ensured a dramatic increase in soil moisture. At the same time, in the upper 30 cm layer of chernozem, its amount became “good”. In August, the drying of the soil profile continued. Ornamental plants grown in the arboretum definitely required additional moisture. In the root horizon, the amount of moisture should be 59 mm. For one meter layer, this value should be 251 mm. Since in June the available moisture amounted to 1.3 mm only, the moisture deficit there reached almost 58 mm, therefore, 580 t ha of water was required for the required moistening of the studied layer of chernozem (56 L per 1 m<sup>2</sup>). In August, the available amounted to 23 mm. Based on this, irrigation was required at a rate of 360 t ha which amounted to 36 kg m<sup>2</sup>. The dry winter of 2019 led to unfavorable soil moisture conditions. In the humus-accumulative horizon, the amount of available moisture varied during the spring-summer period from 42 to 14 mm, decreasing over time to unsatisfactory values. Therefore, to moisten the root layer to 0.75 of the minimum water capacity, it was necessary to irrigate with irrigation rates of 280 t ha and 560 t ha, respectively, or 42 and 56 liters per square meter.