[en] In order to increase potato yields by drip irrigation and fertilization; and also to improve nitrogen and water use efficiencies of potato and eventually to obtain less nitrogen polluted surface and ground water, field experiments were carried out for three years at three different locations in Cappodocia Region of Turkey. Following treatments were investigated in field experiments: 1) N₀= Control, no nitrogen fertilizer application and drip irrigation; 2) N₁=300 kg N/ha fertilizer applied by means of fertilization, 3) N₂= 600 kg N/ha fertilizer applied by means of fertilization, 4) N₃=900 kg N/ha fertilizer applied by means of fertilization, 5) N₄=600 kg N/ha fertilizer applied on the soil surface and drip irrigation. Ammonium Sulphate was used as nitrogen fertilizer in all experiments.¹⁵N - labelled Ammonium Sulphate fertilizer were applied in isotope-sub plots for each treatment in order to determine the amount of nitrogen taken up by the plant, nitrogen use efficiency and the distribution of residual nitrogen at different depths in the soil profile. Soil water contents at different soil depths were determined by soil moisture neutron probe and water use efficiencies were calculated for each treatment. The results obtained show that a) by applying 44 % less water with drip irrigation equal amount of marketable tuber yields were obtained, b) nitrogen fertilizer was used more efficiently under drip irrigation compared to sprinkler irrigation which eventually indicated less leaching of nitrogen fertilizer

[en] A study was carried out between 2008 and 2012 to evaluate the effect of water stress on wheat crop using carbon isotope discrimination (Δ¹³C) and oxygen isotopic ratio (¹⁸O/¹⁶O) and to define crop water parameters through infrared thermometry and porometry, and determine relationship between these parameters and isotopic ratios of C & O at field scale, to calculate water-use efficiency (WUE [g grain yield/m²/mm ET]) for wheat under different water applications. Field experiments were conducted with 4 irrigation treatment (no irrigation; I₁, low: I₂, moderate: I₃ and high irrigation stress: I₄) at Saraykoy Research Station in Ankara-Mürted Basin. Additionally for 2011–2012 growing season, an irrigated treatment on a large field (5 ha) was carried out to evaluate E&T partitioning using the Keeling plot method. In all the above studies, soil moisture was measured with neutron probe. Infrared thermometer and porometer devices were used to measure canopy temperature, stomatal conductance on plant samples. Isotope compositions of carbon and oxygen were determined from soil, plant and atmospheric water vapour. At the end of the study average wheat yields were 3.35 t/ha, 4.54 t/ha, 4.22 t/ha and 4.31 t/ha, respectively for the I₁, I₂, I₃, I₄ treatments. The highest yield was obtained from the full-irrigation treatment while the lowest yield was obtained from the no-irrigation treatment. Average harvest index values were found to be respectively 29%, 31%, 32% 31% and 32%, again according to the treatments. The proportion of transpiration as percent of total ET was between 70.5 to 96% before irrigation while it was approximately 70% after irrigation. A significant positive relationship was found between carbon discrimination (Δ) and yield ratio of both grain and leaf, while a significant but negative correlation between the water-use efficiency (WUE). The positive relationship between the stomatal conductance and yield and the increase of the transpiration from the pores in environments without any irrigation restriction indicate an increase in the plant biomass and yield. This result showed that WUE is more strongly dependent on stomatal conductance. The study showed that irrigation should be recommended to be applied after heading period which increases WUE in Central Anatolia Region of Turkey. Crop water stress index is a useful tool for detecting crop water stress. (author)

[en] In order to evaluate potato response to drip irrigation and N fertigation; and also to improve nitrogen and water use efficiencies of potato and eventually to obtain less nitrogen polluted surface and water, 10 field experiments were carried out at three different locations in Cappadocia Region of Turkey in 1997, 1998, 1999 and 2000 growing seasons. Nitrogen as ammonium sulphate ((NH₄)₂So₄), was supplied by drip irrigation water (fertigation) at rates of 0, 30, 60 and 90 kg N/da. Also, soil N application treatment equivalent to the fertigation treatment of 60kg N/da was included. These five treatments were investigated in a completely randomized block design with four replicants. Agria potato variety was used in all experiments and potato was planted in mid May and harvested at the end of October.''1''5N-labelled ammonium sulphate fertilizer were applied in isotope-sub plots within the macroplots for each treatment, in order to determine the amount of nitrogen taken up by the plant, nitrogen use efficiency and the distribution of residual nitrogen at different depths in the soil profile. Each year, during the growth period, total 12 irrigations were done and 50 mm of water was applied at each irrigation. At harvest, plant samples (tuber and leaf+vein) and soil samples were taken from each plot and N%, ''1''5N% atom excess (''1''5N% a.e.) and Ndff% determinations were done. Soil water contents at differrent soil depths were determined by soil moisture neutron probe at plantingand at harvest period so that water contents at different soil layers and water use efficiencies were calculated for each treatment. The results obtained showed that 3350 kg/da mean total marketable tuber yield was obtained with application of 600 mm irrigation water. Also,it was found that water did not move below 90 cm of soil layer in drip irrigation-fertigation system, which showed clearly that no nitrogen movement occured beyond 90 cm soil depth. Tuber yields and %Ndff increased when nitrogen is applied with drip irrigation-fertigation system in comparison to the application to the soil and then drip irrigation. At harvest, more nitrogen was accumulated at shallower depths with fertigation treatments