Factors Determining Spatial Variability of Some Nutrient Elements in Soils of Ayas Research and Training Farm

This study was conducted at fields of Ayag Research and Training Farm soils of Agricultural Faculty of Ankara University to determine spatial variability of total nitrogen (TN), available phosphorus (YP) and exchangeable potassium (EK) contents and affecting soil factors their variability. Total of 100 soil samples taken from 0-30 cm soil depth in the study area that has 43.5 hectares land area with 4 different soil series were analyzed. In addition, 46 soil samples were collected from intersect points in grid lines sized 100x100 m polygons in the study area. Moreover, 54 soil samples were taken from 9 transects set up with 3, 8, 10, 25, 60 and 80 m interspaces on these polygons. Firstly, to determine spatial variability, descriptive statistics were generated and then theoretical semivariogram were calculated for each parameter and variation maps were created by kriging method. Levels of TN and EK investigated nutrient elements in this research in terms of their availability plant growth were found adequately levels whereas, available phosphorus level was ranged from inadequate to adequate levels. It was obtained the highest R^2 value (0.394) for TN whereas, the lowest R^2 value (0.105) was foundfor EK in determining of soil factors effected on variation ofplant nutrient elements. In addition to that, the higher estimations can be made addition of some properties such as land use, parent material and topography and so on to regression model.