A new approach for calculating aggregate stability: Mean weight aggregate stability (MWAS)

Many different methods have been proposed to determine aggregate stability. In most of these methods, certain aggregate size is used to estimate the aggregate stability of the whole soil. Determination of aggregate stability on a certain aggregate size is insufficient to represent the aggregate stability of the whole soil and the results are strongly dependent on the size chosen. Therefore, the determination of aggregate stability should include all aggregate sizes and the quantities of the soil investigated. The Mean Weight Aggregate Stability (MWAS) is a new calculation method, which is calculated by the sum of multiplying the proportional coefficient of each aggregate size (W-1) by the aggregate stability of each aggregate size (AS). Soil samples collected from 15 different fields are separated into 17 different aggregate sizes by dry-sieving, weighted, and then aggregate stability of each size is determined using a Yoder type wet sieving apparatus. Aggregate stability was significantly affected by the aggregate size and, in general, stability increased as the size of dry aggregates increased (r = 0.934 ** ). While the mean lowest aggregate stability value was determined in the < 0.25 mm aggregate size, the highest was determined in the 38.1-50.8 mm. Results of comparison tests between MWAS and AS, are found to change from soil to soil, which indicates that a certain size aggregate stability may not correctly represent the aggregate stability of the whole soil. The highest similarities between MWAS and AS, were obtained in 10-12, 8-10, and 6-8 mm aggregate sizes. Results obtained from this study indicated that single-sized aggregate stability is not sufficient to express the aggregate stability of the whole soil. Therefore, the use of MWAS instead of the aggregate stability established by a certain size is believed to be a better index for evaluating the aggregate stability of the whole soil.