Summary:

The aim of the paper was the comparison of sour cherry-tree water requirements in the regions of Bydgoszcz and Wrocław in 1976-2015. The sour cherry-tree water requirements were determined for each year on the basis of air temperature in the period April - August for light soils, medium soils and heavy soils. The sour cherry-tree water requirements in the period April - August in the region of Wrocław were higher than those in the Bydgoszcz region. The sour cherry-tree water requirements in the Bydgoszcz region amounted 253 mm on the heavy soils, 316 mm on the medium soils and 379 mm on the light soils. The sour cherry-tree water requirements in the Wrocław region amounted 261 mm, 326 mm and 391 mm, respectively. From among five months, July was characterized by the highest water requirements. The water requirements in July in the Bydgoszcz region amounted 65 mm on the heavy soils, 82 mm on the medium soils and 98 mm on the light soils. The water requirements in July in the Wrocław region were higher and amounted 67 mm, 84 mm and 101 mm, respectively. In the vegetation period (IV-VIII), the significant tendency to increase the water requirements of sour cherry-tree in both observed regions was noted; stronger relationships occurred for the Wrocław region. The analyzes show that the water requirements of sour cherry-tree in IV-VIII rose in each decade (ten years) by 3.9 mm on the heavy soils, 4.9 mm on the medium soils and 5.9 mm on the light soils in the Bydgoszcz region and by 8.6 mm, 10.7 mm and 12.8 mm, respectively, in the Wrocław region. From among months, the strongest increase of water requirements occurred in July. The water requirements of sour cherry-tree in July rose in each decade (ten years) by 2.5 mm on the heavy soils, 3.2 mm on the medium soils and 3.8 mm on the light soils in the Bydgoszcz region and by 3.1 mm, 3.9 mm and 4.6 mm, respectively, in the Wrocław region. The average rainfall deficiencies in the studied forty years (which can be treated as irrigation requirements) were dependent on the soil heaviness. They were the highest on the light soils. In the vegetation period (IV-VIII) they amounted 115 mm (maximum: 160 mm) in the Bydgoszcz region and 72 mm (maximum: 113 mm) in the Wrocław region.