Summary:

Poland is the biggest producer of apple in Europe. Rainfalls are basic source of water for plants. The climate of Poland is characterized by high temporal and spatial variation that makes estimation of plant water requirements and forecasting of water balance difficult. The aim of the study was assessment of water needs of apple trees as well as amount of effective precipitation, enabling estimation of irrigation requirements.
Data was collected during vegetative periods (May - Sep.) of 2011 - 2016. Analysis of data from different years and locations revealed that in Polish conditions climatic water balance accurately reflects balance of water requirements of apple trees only in June. In May values of climatic water balance were significantly higher, whereas in July, August and September lower compared to balance of apple water requirements.