Effect of soil tillage on soil organic matter in a clay field

In this study, effect of soil tillage on spatial variability of soil organic matter content (OM) in a clay field was determined by geostatistical method. The clay field was cultivated using a mouldboard plough at a depth of 15 cm. After conventional tillage, soil samples were taken from a square grid at 5 m spacing of a 30 x 30 m2 plot selected in the clay field. Soil OM contents of the samples varied between 2.03 % and 2.98 %. Clay content (31.48 to 43.97 %), bulk density (BD) (1.12 to 1.41 g/cm3), total porosity (F) (46.79 to 57.73 %), volumetric water content (θ) (19.64 to 43.86%), soil pH (6.47 to 7.40) and electrical conductivity (EC) (0.31 to 0.80 dS/m) values also showed variations among the soil samples. In kriging interpolation for the spatial variability of SOM, the biggest r2 (0.766) and the smallest RSS (0.0013) values were determined with Gaussian model. Spatial dependences of the SOM was strong in the field with 6.4 of nugget/sill ratio. The semivariogram of SOM showed spatial dependence with a range of 157.61 m. SOM had significant positive correlations with clay (0.365**), F (0.287*) and significant negative correlations with BD (-0.286*), θ (-0.362*) and silt (-0.429**) content. This study showed there is a spatial variability of SOM in arable fields, it can be predicted for precision agricultural practices and monitoring organic carbon in global warming researches by geostatistically. Keywords: Soil organic matter, tillage, soil properties, spatial variability, kriging