Ebru Karnez

Phosphorus Use Efficiency of Wheat Genotypes Grown in Calcareous Soils

ABSTRACT Phosphorus (P) deficiency and low P-use efficiency are induced by soil properties, especially in calcareous soils, which are dominant in semi-arid regions of the world such as the Mediterranean region. Alternative approaches to P fertilization involve exploiting plant genetics in order to achieve more efficient use of P by the growing crop. Accordingly, in a greenhouse pot experiment, we evaluated P-efficiency in wheat genotypes grown in typical calcareous soils in southern Turkey. Ten common local genotypes were grown in six soil series for eight weeks using five P application rates (0, 25, 50, 100, and 200 mg P kg−1). Dry matter (DM) yield and P content were significantly increased by increasing P rates, with significant differences between soils. Some genotypes performed better under P stress because of better P utilization efficiency. Shoot DM was the most sensitive indicator of genetic variability under P-deficient conditions. Genotypes classified as efficient-responsive (Adana-99, 1014, Golia, Balatilla) had above average DM yield when P was not added, and responded well to P applications; efficient-non-responsive genotypes (Firat-93, Seri-82, Genc-99, Panda) had below average DM yield, but responded to P applications; inefficient-non-responsive genotypes (Fuat Bey and Ceyhan-99) had below average DM yield; and no genotypes were in the inefficient responsive category. Such P response categorization is needed for better breeding programs for nutrient-use efficiency. The study may aid in selecting P-efficient genotypes in low-P soils, especially where little P is used. The use of P-efficient genotypes should be seen as complement to, rather than a substitute for, chemical P fertilization depending on local conditions.

Genotypic Responses of Corn to Phosphorus Fertilizer Rates in Calcareous Soils

In the Mediterranean region, much emphasis is placed on the role of fertilizers in enhancing crop production to achieve food security. Given the complex nature of phosphorus (P) reactions in soils, considerable research has dealt with fertilizer aspects related to efficient P use, but comparatively less emphasis has been given to plant variation with respect to P efficiency. In this study, selection and adaptation of P‐efficient corn genotypes was seen as one possible approach to enhancing P efficiency. Thus, a greenhouse experiment with 10 corn genotypes (traditional to modern), five P application rates (0–200 mg kg−1), and four field trials with three genotypes for 2 years were carried out on various calcareous soils (Vertic Torrifluvent, Vertic Calciorthid, Entic Chromoxerert, and Typic Xerofluvent). Measurements were made of root characteristics. Treatments in the field trials were five P application rates as main plots (0–68 P ha−1) and three corn genotypes as subplots. Genotypes were selected for the field trials from the greenhouse experiment as “efficient‐responsive,” “efficient‐nonresponsive,” and “inefficient‐responsive.” Dry‐matter (DM) yield and plant P uptake by plants increased with P application rates in the greenhouse experiment. Root length and mass were considerably increased by increasing P levels. Genotypes were classified for P efficiency. The studies indicated that because corn genotypes respond to P‐fertilizer application differently, this trait could be utilized to exploit native and applied P more efficiently, especially at low levels of available P and when P‐ fertilizer use is limited. This differential response derives from morphological, physiological, and genetic variability among the genotypes. Although genotypic efficiency is important for fertilizer management, the contribution of the efficiency is not a substitute for fertilizers, especially if high yields are required. Nevertheless, breeding for P‐use efficiency should be a component of any program to improve crop yield potential.

Diallel Analysis of Wheat Parents and Their F2 Progenies under Medium and Low Level of Available N in Soil

ABSTRACT Due to high production cost and prevention of environmental pollution, it is important to reduce the amount of nitrogen (N) fertilizer used on wheat (Triticum aestivum L.). The aim of this study was to evaluate N use of 6 × 6 diallel wheat F2 progenies and parental lines at low (N0, no N fertilizer) and high (N+, 160 kg N ha− 1) N levels. Significant differences were found between N+ and N0 application in grain N content, grain N yield, N use efficiency for grain N yield (NUEgn), and N use efficiency for grain yield (NUEgy). The cultivar ‘84ÇZT04’ showed positive and high general combining ability (GCA) effects for all traits at low N level. Also, it was the best combiner for all traits at both N levels. The cultivar ‘Genç 99’ was the best parent for GCA effects for grain yield and NUEgy. Hybrids ‘Genç 99 × 84ÇZT04’ and ‘84ÇZT04 × Weaver’ showed positive specific combining ability (SCA) effects for all investigated traits at low and high N levels. Variety ‘84ÇZT04 × Apogee’ had the best SCA effects for all traits at low N level. Overall, the data suggest that it is probable to select promising lines suitable for low N conditions by the crossing of high N use efficient parents.

Modeling Agricultural Land Management to Improve Understanding of Nitrogen Leaching in an Irrigated Mediterranean Area in Southern Turkey

Nitrogen (N) cycle dynamics and its transport in the ecosystem were always an attracting subject for the researchers. Calculation of N budget in agricultural systems with use of different empirical statistical methods is common practice in OECD and EU countries. However, these methodologies do not include climate and water cycle as part of the process. On the other hand, big scale studies are labor and work intensive. As a solution, various computer modeling approaches have been used to predict N budget and related N parameters. One of them is internationally established Soil and Water Assessment (SWAT) model, which was developed especially for modeling agricultural catchments. The aim of this study was to improve understanding of N leaching with simulation of agricultural land management (fertilization, irrigation, and plant species) in hydrological heavily modified watershed with irrigation-depended agriculture under Mediterranean climate. The study was conducted in Lower Seyhan River Plain Irrigation District (Akarsu) of 9495 ha in Cukurova region of southern Turkey. Intensive and extensive water and nitrogen monitoring data (2008–2014), soil properties, cropping pattern, and crop rotation were used for the SWATmodel build, calibration, and validation of the model.

Considering Residual Soil Mineral Nitrogen in Corn Fertilizer Recommendations in an Irrigated Mediterranean Area

ABSTRACT Management of nitrogen (N) fertilization for economic crop production in water-stressed areas relies heavily on irrigation. The objectives were to determine the depth distribution of mineral N (Nmin) at pre-plant and post-harvest seasons and assess the residual mineral N pool as a potential source of plant-available N for irrigated corn (Zea mays L.) in southern Turkey. Pre-plant and post-harvest composite soil samples were collected randomly from farmer’s fields at 0–30, 30–60 and 60–90 cm depths, respectively, analyzed for nitrate (NO3) and ammonium (NH4) concentrations, and the Nmin values were correlated with corn yields and N uptake. Results showed that substantial amounts of pre-plant (76 to 94 kg Nmin/ha) and post-harvest (70–78 kg Nmin/ha) Nmin accumulation at different soil depths. However, the Nmin did not correlate with crop yields and N uptake. Results suggested that residual Nmin could be the basis for recommending N fertilization to support crop production.