Investigation on spatial variability of aggregate stability and the factors affecting soil aggregation using kriging geostatistics method (Case study: A part of Taleghan watershed)

The spatial pattern of soil properties can be a key element in shaping water and nutrient flows in ecosystems and its identification is relevant for understanding soil processes in these areas, and then establishing adequate management practices. One of the factors affecting soil erosion is aggregate stability and its change. If factors affecting aggregate stability and soil aggregation are determined and also appropriate method and spatial variability index is characterized, it can overcome the limitation in this context. To this end, an investigation on the part of Taleghan watershed with area of approximately 3200 hectare and mainly bedrock marl of tertiary including rock units of gy (red mudstone and gypsum silt) and Ngm (red mudstone and silt) was conducted. Aggregate stability and factors affecting soil aggregation was measured using Le Bissonnais method and Pearson correlation test respectively. Spatial variability of aggregate stability and the factors affecting it was studied using kriging method. In classical statistic part, results showed that soil physico-chemical properties including clay, fine sand, very fine sand contents, moisture saturation, Caco3 and organic matter percentages are effective on aggregate stability in studied area. Geostatistical results also showed that spatial dependence of most of the factors affecting soil aggregation are weak to moderate, so that only measurement error of organic matter is low, which implies high dependencyand low random variance of variable distribution in studied soils. This means that organic matter content in samples close together is very similar and is very different from the ones farther. Aggregate stability indices are anisotropic and influence range min and max are from 740 to 2500 and 3250 to 5940 meters respectively.