Abstract
The goal of this study was to assess the water needs of elderberry. The investigation included elderberry plants that had been planted in land reclamation areas more than three years earlier. The water needs were evaluated for 5 agro-climatic regions of Poland. The calculations were based on the observation of meteorological conditions in the years 1981-2010 for the period from June 1 to July 31. To determine the water needs, the plant coefficient method was applied. The Blaney-Criddle formula, which was modified for Polish conditions by Żakowicz (2010), was used to calculate the reference evapotranspiration. The plant coefficients of elderberry, adapted to the reference evapotranspiration, were adjusted to Żakowicz’s method. The rainfall deficit with the probability of occurrence: N50%, N25% and N10%, was assessed in accordance with Ostromęcki’s method. The highest water needs of elderberry occurred in central-north-west (264 mm) and central-east (262 mm) Poland, while the lowest (244 mm) in the south-east region. In June, the highest total monthly water needs (119 mm) were noted for south-west Poland, whereas the lowest (107 mm) for the south-east region. In June and July, except for the central-north-west region, an upward time trend of water needs was noted throughout Poland. In June and July, the highest value (135 mm) of rainfall deficit N50% and N25% was estimated for the central-north-west region, while the highest rainfall deficit N10% (269 mm) for central-east Poland. The results of the presented research find application in the planning of irrigation treatments for elderberry in Poland.