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Baskan O.,Soil Fertilizer and Water Resources Research Institute | Kosker Y.,Soil Fertilizer and Water Resources Research Institute | Erpul G.,Ankara University
Environmental Monitoring and Assessment | Year: 2013

Modeling spatio-temporal variation of soil moisture with depth in the soil profile plays an important role for semi-arid crop production from an agro-hydrological perspective. This study was performed in Guvenc Catchment. Two soil series that were called Tabyabayir (TaS) and Kervanpinari (KeS) and classified as Leptosol and Vertisol Soil Groups were used in this research. The TeS has a much shallower (0-34 cm) than the KeS (0-134 cm). At every sampling time, a total of geo-referenced 100 soil moisture samples were taken based on horizon depths. The results indicated that soil moisture content changed spatially and temporally with soil texture and profile depth significantly. In addition, land use was to be important factor when soil was shallow. When the soil conditions were towards to dry, higher values for the coefficient of variation (CV) were observed for TaS (58 and 43 % for A and C horizons, respectively); however, the profile CV values were rather stable at the KeS. Spatial variability range of TaS was always higher at both dry and wet soil conditions when compared to that of KeS. Excessive drying of soil prevented to describe any spatial model for surface horizon, additionally resulting in a high nugget variance in the subsurface horizon for the TaS. On the contrary to TaS, distribution maps were formed all horizons for the KeS at any measurement times. These maps, depicting both dry and wet soil conditions through the profile depth, are highly expected to reduce the uncertainty associated with spatially and temporally determining the hydraulic responses of the catchment soils. © 2013 Springer Science+Business Media Dordrecht.

Baskan O.,Soil Fertilizer and Water Resources Research Institute | Cebel H.,Soil Fertilizer and Water Resources Research Institute | Akgul S.,Soil Fertilizer and Water Resources Research Institute | Erpul G.,Ankara University
Environmental Earth Sciences | Year: 2010

Soil erosion is a major environmental problem that threatens the sustainability and productivity of agricultural areas. Assessment and mapping of soil erosion are extremely important in the management and conservation of natural resources. The universal soil loss equation (USLE/RUSLE) is an erosion model that predicts soil loss as a function of soil erodibility (K-factor), as well as topographic, rainfall, cover, and management factors. The traditional approach assumes that one soil erodibility value represents the entire area of each soil series. Therefore, that approach does not account for spatial variability of soil series. This study was carried out to evaluate the use of the sequential Gaussian simulation (SGS) for mapping soil erodibility factor of the USLE/RUSLE methodology. Five hundred and forty-four surface soil samples (0-20 cm) were collected from the study area to determine the soil erodibility. A simulation procedure was carried out on 300 realizations, and histogram and semivariogram of the simulation were compared to the observed values. The results showed that the summary statistics, histogram, and semivariogram of the simulation results were close to the observed values. In contrary to the traditional approach and kriging, 95% confidence interval of the simulated realizations was formed in order to determine uncertainty standard deviation map, and the uncertainty was explained numerically. The SGS produced a more reliable soil erodibility map and it can be more successfully used for monitoring and improving effective strategies to prevent erosion hazards especially to improve site specific management plans. © 2009 Springer-Verlag.

Dengiz O.,Ondokuz Mayis University | Saglam M.,Ondokuz Mayis University | Ozaytekin H.H.,Selcuk University | Baskan O.,Soil Fertilizer and Water Resources Research Institute
Carpathian Journal of Earth and Environmental Sciences | Year: 2013

Soil formations were highly associated with topographic positions which have influence on morphological, mineralogical and weathering process of the soils. Because, topography or relief affects how water and other material are added to and removed from soils. The aim of this study is to carry out apedological assessment of the soils classified as Regosol, Cambisol and Vertisol by taking into considerationFAO classification system formed on different topographic position and the same parent rocks (limestonemarl).In addition the second aim of this research is to answer the question about the difference in classificationresulting from pedogenic processes or from other factors by determining the degree of weathering soils usinggeochemical data. For this aim, after macro-morphological identifications were completed for threerepresentative soil pedons, the soil samples were then collected from the horizons to investigate the analyticalcharacteristics such as mineralogical, geochemical and physio-chemical properties. The study will also takeinto account other features such as the pedogenic evolution of soils using weathering indices such as CIA,CIW, Base/R2O3, WIP and PIA. According to results, CIA, CIW, PIA and WIP index values of all soils variedbetween 66.75-73.87, 73.48-81.79, 57.60-68.49, respectively. In addition it was found that the bases/R2O3 values of most of the soils were below 1.0. The results clearly showed that topographic condition stronglyaffects on soil physic-chemical, mineralogical and morphological properties either directly or indirectly in thelocal region. This case was also explained with chemical weathering indices in this study.

Mihalikova M.,Czech University of Life Sciences | Baskan O.,Soil Fertilizer and Water Resources Research Institute | Dengiz O.,Ondokuz Mayis University
Environmental Earth Sciences | Year: 2015

Many catchment basins have insufficient data to make conservation planning for sustainable natural resources use. In addition, intensive soil sampling is neither feasible nor economical in a large studied area. Therefore, interpolation models and pedotransfer functions (PTFs) have important roles in data mining. Main objectives of this study were to estimate and evaluate the estimates of basic soil hydraulic properties in Büyükçay Watershed (Turkey) using different interpolation geostatistic models and PTFs. Three interpolation models (inverse distance weighting IDW, ordinary kriging and cokriging) and pedotransfer functions (continuous and class) were applied and compared in this study. In 84 soil samples, soil depth, texture, organic matter, pH, electric conductivity, saturation degree, field capacity and permanent wilting point were determined. According to the results, among geostatistical algorithms, ordinary cokriging yields better results for all soil hydraulic properties with lower MAE and MSE values than ordinary kriging and IDW. Within PTFs, soil hydraulic properties were estimated with high reliability using continuous approach; however, class PTFs showed less sensitivity to space variability than geostatistical methods. © 2015, Springer-Verlag Berlin Heidelberg.

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