OPTIMUM NITROGEN SUPPLY FOR LEEKS AT TWO CLIMATIC CONDITIONS IN THE BALTIC SEA REGION

The objective of our experiments was to verify the recommendation of 220 kg ha^-1 for optimum N supply for leeks grown at two locations with unlike climatic conditions. At the Aarslev site in Denmark and the Babtai site in Lithuania, leeks were grown at six N rates ranging from 100 to more than 400 kg ha^-1 inclusive the N_min content in the top 0.5-0.6 m soil layer in spring. At both experimental sites, the yield increased with increasing N supply and the maximum production was obtained at the highest supply. The N uptake increased from 118 to 180 and from 83 to 193 kg ha-1 in the Aarslev and Babtai experiment, respectively. At increasing N supply, the content of nitrate increased whereas the content of sugar and vitamin C decreased. If the total N supply exceeded 200-250 kg ha^-1, the soil N_min residues at harvest increased considerably.