Application of different models to the lactation curves of unimproved Awassi ewes in Turkey

The objective of this study was to investigate the use of four different mathematical functions (Wood, Inverse Polynomial, Quadratic and Cubic models) for describing the lactation curve of unimproved Awassi ewes. Data were collected from 136 ewes from the same flock raised on the State Farm of Gözlü in the Konya Province of Turkey. The differences in estimated total milk yields between the models were not statistically significant. All models were adequate in describing total milk yield, though total milk yield estimated using the Cubic model was very close to total milk yield calculated by the Fleischmann method. Age effects on model parameters were not significant. The Inverse Polynomial model overestimated the peak yield significantly. Estimated peak yields of the Wood and Cubic model were similar while that obtained from the Quadratic model was significantly lower than that of the other models. Day of peak yield estimated by the models varied between 10.2 and 56.4 days. The differences between days of peak yield estimated using the different models were significant. R2 values of the models ranged from 0.724 to 0.977. The Cubic model gave the best R2 value. The lowest mean square prediction error was found using the Cubic model. Correlation coefficients between total milk yield calculated by the Fleischmann method and estimated total milk yield from the other models ranged from 0.933 to 0.998. The highest correlation coefficient was found for the Cubic model. As a result, the Cubic model showed the best fit to the data collected from unimproved Awassi ewes and allowed a suitable description of the shape of the lactation curve. South African Journal of Animal Science Vol. 35(4) 2005: 238-24

An investigation of the criteria used to select the polynomial models employed in local GNSS/leveling geoid determination studies

Ellipsoidal heights are determined with high accuracy using Global Navigation Satellite System (GNSS) techniques. In infrastructure projects undertaken for engineering purposes, orthometric heights are used. Geoid determination studies based on these two height systems are growing in importance. Although various methods are employed in geoid determination, one of the most commonly used in practice is local geoid determination. Points with known orthometric and ellipsoidal heights are used as reference points. These reference points are utilized to determine local geoid models for project area. The formation and selection of the most appropriate and true-to-reality model during modeling are a matter of extreme significance for practitioners who employ such models. In this study, we aim to establish a GNSS/leveling geoid in a test network that was formed in Konya for the purpose of local geoid determination. Validity tests are carried out for five different geoid models. These geoid models are determined using polynomial models of up to the third degree, and an exploration of the parameters that could be used in the decision-making process is performed. In accordance with the results of these calculations, the selection of an appropriate model among different potential polynomial models in local geoid modeling is explained in terms of theoretical references, an application is examined using the data from the study area, and the results are compared. © 2018, Saudi Society for Geosciences

Subsoil Compaction: The Intensity of Manifestation in Silty Clayey Calcic Pantofluvic Fluvisols of the Iğdır Region (Eastern Turkey)

Abstract: The formation of compacted subsoil layer under the impact heavy machines is a global problem in soil science, soil physics, and agrotechnology because of the numerous and significant effects on the water, air, and thermal regimes of soils, their permeability for root systems of plants, etc. For recent calcareous alluvial soils (Calcic Fluvisols) in the foothill areas of eastern Turkey, this problem is particularly important, because these soils were formed as a result of floods of the Aras River. These soils represent unconsolidated homogeneous formations and have a compacted horizon at the depth of 30 to 65 cm, which was formed during dozens of years. Its density almost reaches critical values for loamy soils (>1.5 g/cm3), and its penetration resistance is also high: close to 5 MPa. The studied soils are heavy loamy throughout the profile with a predominance of silt fractions (1–3 and 4–6 µm), have a low content of soil organic matter (up to 0.5% in the plow layer). In the layers of 0–30 cm and 70–150 cm, soil density and penetration resistance are not high: 1.3 g/cm3 and 2 MPa, respectively. Such a fast and deeply penetrating soil compaction is associated with the initial loose state of the soils, their heavy texture, and low content of soil organic matter—the main protector from the subsoil compaction. To prevent further development of subsoil compaction, it is recommended to optimize agrogenic loads, stop using heavy machines under conditions of the high soil water content, and to apply organic fertilizers. © 2019, Pleiades Publishing, Ltd.2221 Türkiye Bilimsel ve Teknolojik Araştirma KurumuACKNOWLEDGMENTS This study was supported by the BİDEB (Department of Science Fellowships and Grant Programs) of the Scientific and Technological Research Council of Turkey (TÜBİTAK), grant 2221

Assessing the impact of azadirachtin application to soil on urease activity and its kinetic parameters

The kinetic parameters of soil urease have attracted considerable attention; however, little information is available on its kinetic parameters and behaviors in response to azadirachtin application to the soil. A short (14-day) field experiment was conducted using Albic Luvisol soil (loam texture; pH 6.70; electrical conductivity 0.81 dS m-1; CaCO3 content 0.04%; total organic carbon 0.99%) as the experimental soil in the Perm region of the Russian Federation to investigate the effects of different azadirachtin application doses on soil urease activity and its kinetic behaviors. The results showed that the highest urease activity was found under high azadirachtin application doses (0.6 L ha-1) compared to the control (0 L ha-1), recommended (0.3 L ha-1), and low (0.15 L ha-1) azadirachtin application doses at all different incubation times (1, 2, 3, 6, and 12 h). Soil urease enzymes exhibited typical Michaelis-Menten kinetic behaviors; high azadirachtin application doses increased the substrate affinity constant (KM) and decreased the maximum reaction rates (Vmax) of soil urease. As compared to the control azadirachtin application dose, the low azadirachtin application dose increased the Vmax of soil urease; however, with low and recommended application doses, the Vmax of soil urease decreased. Overall, in this study, all azadirachtin application doses were effective in influencing the kinetic behavior of urease in Albic Luvisol. © TÜBİTAK