Split application of nitrogen fertilizer on yield producing black, red and white currants: field experiment on commercial farms in 1989-1990

abonado fraccionado abonos nitrogenados azote black currants calcio calcium cassis fertilidad del suelo finland finlande finlandia groseille blanche groseille rouge grosella blanca grosella negra grosella roja magnesio magnesium nitrate nitrates nitratos nitrogen nitrogen fertilizers nutritive value red currants ribes nigrum ribes rubrum soil fertility split dressings valeur nutritive valor nutritivo white currants