عنوان مقاله [English]
نویسنده [English]چکیده [English]
Introduction: Topography is one of soil forming factors through the degree and aspect of slope affect on soil physical properties. The aspect of slope influences soil moisture, temperature and activity of micro organisms cause change soil organic matter in different soil aspects and therefore create different soil qualities. Different solpe degrees through transport of organic and clay particles down parts of the slope and changing bulk density affect the soil quality (15). In order to maximize utilization of agricultural lands and minimal environmental degradation and to prevent soil erosion, study soil quality is essential. The aim of this study was to evaluate soil quality in different degrees of both northern and southern slopes in catchment of Torogh dam, located south eastern of Mashhad.
Materials and Methods: To asses the soil quality, 40 soil samples were taken from 0-30 cm soil depth in both northern and southern slopes consist of less than 10%, 10-20%, 20-30% and more than 30% slope degrees in catchment of Torogh dam, located south eastern of Mashhad. 5 soil samples were collected from each slope degree and and properties such as soil organic matter content, bulk density, CaCO3, sodium adsorption ratio (SAR), mean weight diameter of aggregates, water dispersible clay and silt, sand, silt and clay percent, pH and soil structural stability index (SI ) were measured. The score of each property based on scoring functions and their weights were calculated by dividing the communality value of each property to total communality of all properties in JMP4 software. Then Soil quality index was calculated by multiplying the score and weight of the studied properties and sum of them.
Results and Discussion: According to the results of this research, The significant correlation between the percentage of organic matter, CaCO3, water dispersible clay and silt, silt and clay with soil quality index was positive and, that of soil quality index with mean weight diameter of aggregates and percentage of sand was negative (P < 0.01). The quantitative value of soil quality index in the northern slope was significantly more than that of the southern slope. Because of the optimal values of most soil properties in north aspect, therefore soil quality in this aspect was higher than south one. There was no significant difference between slope degrees in south slope, but in north aspect the difference between different slope degrees with 20-30% was significant (P < 0.05) and soil quality value was the least compared others.
Conclusion: In this research, the effect of slope aspect on soil quality was more than degree, and different slope degrees had no significant effect on soil quality.