Influence of nitrogen fertilization and plant density on yield and nitrogen use efficiency of the potato (Solanum tuberosum L.)

The objective of this study was to evaluate influence of different nitrogen rate and in-row seed spacing on yield, tuber size distribution and nitrogen use efficiency characteristics. Field experiment was conducted at the Gospic on private farm during 2009 growth season. The experiment used a split plot arrangement of treatments in randomized complete block design in four repetitions. Main plots were N supply rates (0, 50, 100, 150, 200 i 250 kg N ha -1 ). Sub plots were in-row seed space (25, 30 and 35 cm). Respectively to control, total tuber yield increased by increased N rate up to 150 kg N ha -1 (20.5 t ha -1 ). As N rate increased ratio of small tubers decreased and the lowest ratio of small tubers (9.86%) was obtained at 150 kg N ha -1 . The total tuber yield decreased for 22% as in-row space increased from 25 to 35 cm, but ratio of medium and large tubers increased marginally. The increased N rate decreased nitrogen use efficiency (NUE), nitrogen utilization efficiency (NUtE) and nitrogen uptake efficiency (NUpE) significantly respectively to control. Varying in-row seed spacing from 25 cm to 35 cm decreased significantly N use efficiency characteristics (NUE, NUtE and NUpE) too. Because there is no the interaction effect it is necessary to continue investigation to find out the best combination N rate x plant density for potato growers.