A. Farshad

Do the Emerging Methods of Digital Soil Mapping Have Anything to Learn from the Geopedologic Approach to Soil Mapping and Vice Versa

The use of soil maps and the feasibility of the existing soil survey procedure are often questioned by both surveyors and users. Thanks to the advances in the fields of remote sensing (RS) and geographic information system (GIS), a new trend – digital soil mapping – is emerging which might have answers to some of the questions. With a glance to some of the definitions and concepts, such as ‘what is a soil?’ and ‘what is the content of a soil map?’ we intend to highlight the complexity of the soil and its mapping. At the same time, we apply some of the geopedologic-oriented techniques of the digital terrain modelling to soil mapping in order to show the role of geomorphology in the mapping. The exercise was carried out as case studies in several areas in Thailand. Various soils at subgroup levels (Fluventic, Arenic, Aquic, Aeric, Ultic, Ustic, Vertic) belonging to the soil orders Entisols, Mollisols, Inceptisols, Alfisols, and Ultisols occur in different geomorphic surfaces, following well the physiographic setup of the landscapes. The case studies demonstrate the conventional predictive mapping (the ITC approach) and the geopedologic approach to soil survey, based on parameterisation of the soil-forming factors and their integration: in one case through applying decision trees, followed up by a statistical validation, and in another case by means of Artificial Neural Network (ANN). It is hoped to open up a discussion, which should lead to (1) clarifying the term ‘digital soil mapping’ and (2) finding out whether or not the shortcomings of the conventional approach of soil mapping can be recovered using the new trend and does the new trend suggest changes in the current definitions and concepts.

Evaluation of the spatio-temporal of soil salinity variation using data mining approach

The issue of temporal and spatial variation in soil salinity is considered as a fundamental element in salinity monitoring. The aim of this study is to develop a framework which integrates image mining techniques with Fuzzy logic methodology to improve the evaluation of spatio-temporal variation of soil salinity in areas with lack of available ground observation. Intensity and duration of salinity was characterized in space by the deviation of the current NDVI at each location from its corresponding temporal mean value. Landsat and ASTER images data was used to provide frequent Normalized Difference Vegetation Index (NDVI) in cultivation phase for a period of 22 years. Evolution of salinity condition before planting season was assessed by applying stepwise regression method on image data for two available dataset. The regression equation was obtained between reflectance value of band three and the measured soil Electrical Conductivity (EC) from field. Validation of the developed algorithm was done by comparing the obtained outputs with 50 ground observations, available salinity reports, and previous soil salinity maps. The result revealed that the proposed framework can be considered as a cost and time effective tool for proper assessment of the spatio-temporal variation of soil salinity.

Soil Resources of Iran: Challenges and Recommendations

Agriculture has been practiced in Iran for millennia. The agricultural land of the country is presently fragile and rather limited, as only about 8% of the total land area is under annual crops and orchards. Soil resources of Iran are now facing big challenges which need to be seriously considered in the country’s sustainable development plan. These challenges include lack of an effective national soil policy, land degradation and desertification (erosion, salinity, declining soil fertility and organic matter, deforestation, soil pollution, deterioration of soil’s physical and biological condition), climate change, water shortage, and land-use changes. To combat these challenges, some recommendations are presented including formulation and implementation of an appropriate national soil policy, improving public awareness on the importance of soil resources, enhancing research quality, providing different thematic soil maps, improving agricultural extension and advisory services, and enabling the soil scientists to contribute and collaborate with other scientists in resolving the challenges facing the country’s soil resources. These recommendations need to be urgently taken by the government to ensure sustainability of soil resources, environmental protection, and, consequently, well-being of the next generations.

Geopedology Promotes Precision and Efficiency in Soil Mapping. Photo-Interpretation Application in the Henares River Valley, Spain

Two approaches to prepare photo-interpretation maps that guide the location of field observations and serve as frames for soil cartography are compared. The physiographic approach is mainly descriptive and aims at separating relief units on the basis of their physiognomic appearance. The geopedologic approach highlights relationships between soils and geoforms and aims at predicting patterns of soil distribution prior to soil survey. Both approaches have been applied in the Henares river valley (Spain). The two interpretation maps are compared in terms of soil pattern and density of delineations.

Adequacy of Soil Information Resulting from Geopedology-Based Predictive Soil Mapping for Assessing Land Degradation: Case Studies in Thailand

Soil is a natural body which delivers important ecosystem services apart from being a medium for plant growth. Soil mapping can be time consuming and expensive. During the 1960s and 1970s, introduction of air photo-interpretation in soil survey through element analysis, physiognomic and physiographic analysis, helped increase mapping efficiency. In the late 1980s, the geopedologic approach to soil mapping amplified the role of geomorphology. It helps understand soil variation in the landscape which increases mapping efficiency. In the present study, the adequacy of soil data resulting from geopedology-based predictive soil mapping for assessing land degradation in three locations in Thailand is assessed. The result shows that the geopedologic approach helps map soil in inaccessible mountain areas. However, for application in land degradation studies all the required soil properties may not be available in a soil map. The effect of land cover and land use management practices on soil properties, such as porosity and compaction having effect on hydraulic conductivity, a parameter used in modelling rainfall-runoff-soil erosion, is usually not reported in soil survey. These data have to be collected separately. For mapping areas susceptible to frequent flood, the geomorphic understanding of the river valley and soil characterization (Fluventic and Aquic) help identify susceptible areas. Similarly, the study shows how the geopedologic approach in combination with digital image processing helps in mapping soil salinity hazard.