Having a history of nearly 150 years in Turkey, potato has become one of the most important agricultural crops of the country. Potato production, processing, marketing and consumption have become a major sector as well. However, regardless of these advancements, the Turkish potato sector has still not reached its full potential. Therefore, different approaches are needed in the Turkish potato sector to overcome chronic problems as soon as possible. This paper summarizes the past and the current situation of the Turkish potato industry and evaluates its weaknesses and strengths.

The potato (Solanum tuberosum L.) is widely planted in the Middle Anatolian Region, especially in the Nigde-Nevsehir district where 25% of the total potato growing area is located and produces 44% of the total yield. In recent years, the farmers in the Nigde-Nevsehir district have been applying high amounts of nitrogen (N) fertilizers (sometimes more than 900 kg N ha(-1)) and frequent irrigation at high rates in order to get a much higher yield. This situation results in increased irrigation and fertilization costs as well as polluted ground water resources and soil. Thus, it is critical to know the water and nitrogen requirements of the crop, as well a,, how to improve irrigation efficiency. Field experiments were conducted in the Nigde-Nevsehir (arid) region on a Fluvents (Entisols) soil to determine water and nitrogen requirements of potato crops under sprinkler and trickle irrigation methods. Irrigation treatments were based on Class A. pan evaporation and nitrogen levels were formed with different nitrogen concentrations.The highest yield, averaging 47,505 kg ha-1, was measured in sprinkler-irrigated plots at the 60 g m(-3) nitrogen concentration level in the irrigation treatment with limited irrigation (480 mm). Statistically higher tuber yields were obtained at the 45 and 60 g m-3 nitrogen concentration levels in irrigation treatments with full and limited irrigation. Maximum yields were obtained with about 17% less water in the sprinkler method as compared to the trickle method (not statistically significant). On the loam and sandy loam soils, tuber yields were reduced by deficit irrigation corresponding to 70% and 74% of evapotranspiration in sprinkler and trickle irrigations, respectively. Water use of the potato crop ranged from 490 to 760 turn for sprinkler-irrigated plots and 565-830 mm for trickle-irrigated treatments. The highest water use efficiency (WUE) levels of 7.37 and 4.79 kg m(-3) were obtained in sprinkle and trickle irrigated plots, respectively. There were inverse effects of irrigation and nitrogen levels on the WUE of the potato crops. Significant linear relationships were found between tuber yield and water use for both irrigation methods. Yield response factors were calculated at 1.05 for sprinkler methods and 0.68 for trickle methods. There were statistically significant linear and polynomial relationships between tuber yield and nitrogen amounts used in trickle and sprinkler-irrigated treatments, respectively. In sprinkler-irrigated treatments, the maximum tuber yield was obtained with 199 kg N ha(-1). The tuber cumulative nitrogen use efficiency (NUECU) and incremental nitrogen use efficiency (NUEin) were affected quite differently by water, nitrogen levels and years. NUEcu varied from 16 to 472 g kg(-1) and NUEin varied from 75 to 1035 g kg(-1) depending on the irrigation method. In both years, the NH4-N concentrations were lower than NO3-N, and thus the removed nitrogen and nitrogen losses were found to be 19-87 kg ha(-1) for sprinkler methods and 2589 kg ha(-1) for trickle methods. Nitrogen losses in sprinkler methods reached 76%, which were higher than losses in trickle methods. (c) 2005 Elsevier B.V. All rights reserved.

Soils in the Cappadocia region of Turkey are mainly light-textured (sandy, loamysand, or siltloam) and the prevailing irrigation method used by the farmers is sprinkler. Due to the very high N fertilizer and water usage (nearly 100 kg N/da and 1400-1700 mm of water, respectively) by the farmer in the region for the potato production, some researchers (Karaca and Demir, 1994; Halitligil et al., 2002) conducted field experiments at different locations in the region. Karaca and Demir, 1994 reported that 550 kg N/ha is the economical rate for potato under these light-textured soils. Halitligil et al., 2002 conducted field experiments with potato using 15N labelled fertilizer in order to find out the N balance under sprinkler irrigation in the region rate. Their results showed that nearly half of the applied fertilizer N (45.6 %) at 40 kg N/da rate and more than half of the applied fertilizer N (60.8 %) at 100 kg N/da rate was in 0-200 cm depth in the soil after harvest. In the region, the water for irrigation, animal and as well as human use is directly pumped from the ground water resources due to lack of other resources. As a result of their their findings, the researchers suggested that some agricultural measures to prevent or decrease the nitrate contamination of ground waters (as changing the prevailing sprinkler irrigation system to the drip irrigation-fertigation system) must be taken after the completion of the necessary investigations of the new irrigation + fertigation system in the region.