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¹ Doç.Dr. Tarla Bitkileri Merkez Araştırma Enstitüsü, ANKARA
² Dr. Tarla Bitkileri Merkez Araştırma Enstitüsü, ANKARA - In potato growing region of the Capodocia, farmers apply 700 - 900 kg N/ha with 15-17 times of sprinkler irrigation in the sandy soils, as general practice. This implies that high amount of nitrogen may leach that has adverse effects on environment as well as production costs. Series of trials were conducted in order to find rate and application time of nitrogen fertilizer under farmers conditions. Amount of inorganic (N03 and NH4) nitrogen and distribution in soil profiles of 120 cm soil depth were measured via soil samples. Amounts of NH4 and N03 nitrogen present in the soil profile was highly affected by the rate of nitrogen fertilizer application in spite of variation through years and locations. Average of the four trials that application was done at sowing and earthing up; ammonium nitrogen rate varied 34.8 to 83.0 kg/ha and nitrate nitrogen 29.9 to 230.1 kg/ha with 0, 100, 200, 300, 400, 500, 600, 700 or 900 kg N/ha of nitrogen fertilizer application rate. Ammonium nitrogen has not been effected significantly by application time in general. However, late split applications resulted in higher amount of nitrate in the soil profile. Amount of the NH4 nitrogen has decreased through the deeper layers in soil profile. Nitrate nitrogen measured in deeper layers increased at after the rate of 200 kg N/ha fertilizer applications. Split applications of fertilizer at 1 or 2 months after earthing up caused higher NO3 nitrogen accumulation at upper soil layers (0-30, 30-60, 60-90 cm) in compare to lower (90-120 cm). It is concluded that nitrate even leaches more than 120 cm soil depth with irrigation. Keywords : Potatoes; ammonium-nitrate nitrogen; inorganic nitrogen statues in soil profile