Analysis of changes in the content of selected nutrients in the effluents from the cultivation of everbearing strawberry variety San Andreas in soilless conditions on gutters by Michał Kopeć, Monika Mierzwa-Hersztek, Krzysztof Gondek, Tomasz Zaleski, Stanisław Bogdał, Monika Bieniasz, Jan Błaszczyk, Jarosław Knaga, Jacek Nawrocki, Michał Pniak