IMPACT OF NITROGEN FERTILIZATION AND IN-ROW SEED DISTANCE ON POTATO YIELD, TUBER SIZE AND N RECOVERY

The objective of this study was to evaluate effect of the different nitrogen levels and plant densities on N recovery and yield quality and quantity of potatoes. A split-plot trial with six N levels (0, 50, 100, 150, 200 and 250 kg N ha^-1) as main factor and three in-row seed distances (25, 30 and 35 cm) as sub-factor was conducted on private farm near Gospić (N 44°57’), Croatia during two growing seasons in 2009 and 2010. The total fresh tuber yield increased significantly by N application and by reducing in-row seed distance. There were no significant differences between N levels. By decreasing in-row seed space from 35 to 25 cm total fresh tuber yields decreased mostly by significant increasing portion of small sized tubers and by increasing portion of large sized tubers. Nitrogen recovery increased by plant density and decreased by increasing N application levels.