IMPACT OF FOLIAR NITROGEN AND MAGNESIUM FERTILIZATION ON CONCENTRATION OF CHLOROPHYLL IN POTATO LEAVES ODDZIA£YWANIE DOLISTNEGO NAWOENIA AZOTEM I MAGNEZEM NA ZAWARTOŒÆ CHLOROFILU W LIŒCIACH ZIEMNIAKA

The objective of the study has been to determine the effect of foliar nitrogen and magnesium fertilization on modifications in the concentration of chlorophyll in leaves of an medium-early edible potato cultivar called Zebra. Different rates of foliar magnesium fertilization were applied, fro m0%t o 50 %o f the full dose of this nutrient (80 kgN ha -1 ). The experiment was conducted in three series - without magnesium fertilization, with magnesium applied to soil (24 kgMg ha -1 ) and with magnesium sprayed over leaves (12 kgMg ha -1 ). The highest concentration of chlorophyll a and b was obtained in 2005: 137.6 and 53.4 mg 100 g of fresh mass of leaves. In the same year, the highest yield of potato tubers was produced: on average, 27.86 Mg ha -1 . This relationship, however, was not confirmed in the subsequent years. In 2006 and 2007, the two years with the weather conditions unfavourable to potato cultivation, the volume of yields was positively correlated with the concentration of chlorophyll in leaves, a relationship which was not detected in 2005, when the yield was the highest. Soil or foliar application of magnesium determined the synthesis of chlorophyll and accumulation of yield, especially in the years characterized by unfavourable weather