SOIL QUALITY ASSESMENT OF UPPER TIGRIS BASIN

Abstract

Economic life of the Tigris basin, part of the Mesopotamian depends heavily on agricultural production for thousands of years. Sustainability of agricultural production in this ancient region may only be possible by conserving and improving the ability of soils to function. Therefore, soil quality indexes were computed to evaluate and monitor functioning ability of pasture lands, forest lands, orchard and arable lands in the upper Tigris Basin of Mesopotamian. Soil samples were collected from (0-20 cm) at 134 locations from approximately the corners of 5km*5km size grid cells within 2.450 km(2) research site. Twelve soil properties were measured as potential indicators of soil quality. A minimum data set (MDS) for each of land use was determined by means of principal component analysis (PCA) and expert opinion (EO) techniques. The weightages of each indicator were calculated using PCA and analytical hierarchy process (AHP). Soil quality index (SQI) for every sampling locations was calculated by weighted additive method following the use of linear scoring functions to obtain unitless indicator scores. The organic matter (OM), aggregate stability (AS) and slope were considered the most powerful and common soil attributes for distinguishing land uses in regard to soil quality and they can be used to monitor and assess the soil quality in this semi-arid environment. The SQI values of four land uses were significantly different (P<0.01) from each other. The highest SQI value was obtained for forest land with EO (SQI(EO)=0.974) and the lowest SQI value was for orchards with PCA (SQI(AHp)=0.793). The results indicated that PCA and EO methods produced comparable results in assessment of soil quality.