Investigation the variation of soil mapping units using geopedological approach

The geopedological approach was used for soil mapping from Qazvin province, Iran. A semi-detailed soil survey was performed to select the representative units and the soil profiles were classified according to soil taxonomy and physic-chemical characteristics. By combining the soil and geoform layers, the digital soil map was developed using Arc GIS 9.3 environment and soil was divided into three map units (A, B and C). The soil map unit A showed similar soil properties despite three geoform units were existed. Soil map unit B having single geoform unit also revealed same soil characteristics, whereas unit C soil showed two separate soil classes even in the presence of single geoform unit which was due to the difference in particle size distribution. From the results, it is concluded that the position of landscape profile has a significant effect on determination of soil map units and geopedological approach can be used successfully to evaluate the variation in soil characteristics.