Water Needs of Black Locust (Robinia Pseudoacacia L.) in The First Three Years of Growing in Different Regions of Poland

Abstract

Black locust (Robinia pseudoacacia L.) is appreciated as an ornamental, but also as a honey and medicinal plant. Generally, the trees of this species are planted in the city parks and along streets. Black locust is also used in the soil remediation process, because it enriches the top layer of soil with nitrogen. High seedling survival rate on the reclamation areas determines the success of the first stage of remediation. The use of appropriate cultivars and high quality of seedlings, as well as ensuring sufficient water conditions by irrigation determines the reclamation results. However, firstly, it is necessary to determine the water requirements of the planted species. The aim of the presented study was the estimation of Robinia pseudoacacia L. water needs during the first three years of growing. A commonly used measure of the plant water requirements is a potential evapotranspiration that was calculated in the present study. The modified for Polish conditions by Żakowicz, Blaney-Criddle’s formula, using the adjusted crop coefficients, was applied. The assumption was that the growing period of black locust covers the interval from the beginning of April to the end of October. The calculations were carried out for the thirty years; from 1981 to 2010, in the different agro-climatic regions of Poland. The results presented a rising tendency in the black locust water needs during the growing season for all tested 30 years and in each considered region. The data indicates a gradual increase in the black locust water requirements in all studied regions of Poland. During the analyzed 30 years (1981-2010) the water needs of black locust during the growing season (IV-X) increased in every ten years by 9.8 mm in the central-eastern and south-eastern regions, 9.4 mm in the south-west region, 8.3 mm in the north-east region and 5.8 mm in the north-west region of Poland