In this investigation, the effects of some slow release and conventionally used fast release nitrogen sources in the soils of Nigde-Misli plain on tuber yield, and protein, starch and NO 3 contents of tubers of the potato plants grown under greenhouse condi-tions were determined. Effect of nitrogen levels on tuber yield, as mean of nitrogen sources were found as follows: N 2 >N 1 >N 4 >N 3 >N 0 . On the other hand, increasing levels of nitrogen applied to the soil increased the protein and starch contents of the potato tubers. The highest and low-est tuber yield as mean of N levels was obtained with AS+AZN and AS+PG respectively. According to efficiency of nitrogen sources on tuber yield, nitrogen sources were grouped as; first group AS+AZN, AS+SCU, AZN, FLD; second group FLD, SCU; third group SCU, AS+FLD, AS+N-serve and last group AS, AS+PG. Differences between the groups were is statistically significant (p

In this investigation, the effects of some slow release and conventionally used fast release nitrogen sources in the soils of Nigde-Misli plain on tuber yield, and protein, starch and NO 3 contents of tubers of the potato plants grown under greenhouse condi-tions were determined. Effect of nitrogen levels on tuber yield, as mean of nitrogen sources were found as follows: N 2 >N 1 >N 4 >N 3 >N 0 . On the other hand, increasing levels of nitrogen applied to the soil increased the protein and starch contents of the potato tubers. The highest and low-est tuber yield as mean of N levels was obtained with AS+AZN and AS+PG respectively. According to efficiency of nitrogen sources on tuber yield, nitrogen sources were grouped as; first group AS+AZN, AS+SCU, AZN, FLD; second group FLD, SCU; third group SCU, AS+FLD, AS+N-serve and last group AS, AS+PG. Differences between the groups were is statistically significant (p