Spatial Variation Assessment of Selected Soil Properties for Precision Field Experimentation
Spatial variation and status of selected soil properties were assessed in a small-sized field, cultivated with irrigated corn. A geo-referenced sampling was performed and twenty four soil samples were collected from two depths (0-30 and 30-60 cm) from 12 different locations in order selected soil properties to be determined. Despite the small parcel size, soil properties exhibited a spatial variability, with coefficient of variance (CV) ranging between 7.0 and15.4% for soil texture, 9.9-12.9% for Cation Exchange Capacity (CEC), 12.8-16.8% for organic carbon (Corg) and 15.7-20.6% for total nitrogen (Ntot). CV for Bulk Density (BD) and pH were very low in both soil depths indicating rather high stability.CEC, Corg and Ntot mean values were higher in the top soils. Increased values for pH, clay and CaCO3 contents in the subsurface samples, may be attributed to partial leaching of exchangeable bases and CaCO3. A strong relation between Ntot and Corg found indicating that these elements are mainly bound in the soil organic matter (SOM). A strong negative relation also was recorded between clay content and bulk density (BD) of soils, indicating that BD depends primary on soil texture. In addition, other soil properties showed very low or absence of correlation between each other. Prediction maps have indicated variation in soil properties partially caused by different farming practices. The interpolated maps showed clear differences mainly on Clay, CaCO3, SOM, Norg. and EC across the surveyed area. Application of a simple ordinary kriging clearly demonstrated the spatial variability of soil properties, which should be taken into consideration for designing field experiments, particularly when split-plot factorial block designs are to be used. As shown in this investigation, this can be realized with decreased field work, and lower total cost for laboratory analyses.
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