FRACTAL DIMENSION OF SOIL AGGREGATES - INFLUENCE OF BULK-DENSITY, FITTING PROCEDURE, AND OILY WASTE SLUDGE INCORPORATION

Researchers have used scale-invariant bulk density, p, to estimate val ues of fractal dimension, D, for soil aggregate fragmentation. Justifi cation for this assumption has not been fully explored. The objectives of this study were to compare values of D obtained using (i) scale-in variant and scale-variant p and (ii) linear (defined D(n)l) and nonlin ear (defined D-nl) fitting procedures, and also (iii) to evaluate the influence of oily waste sludge incorporation on D. Aggregate p and mas s-size distribution for a Meota loamy sand treated with different rate s of an oily waste sludge were determined in the laboratory. Bulk dens ity of soil aggregates, average size ranging from 0.21 to 9.55 mm, ran ged from 1.15 to 1.37 Mg m(-3) (R(2) = 0.91). Fifty-four values of D w ere obtained using the scale-variant or scale-invariant p for D-1 or D -nl. Values of DI ranged from 2.23 to 3.83, and those of D-nl from 2.0 7 to 3.15. The values of D obtained using the scale-variant p were alw ays smaller than those obtained using the scale-invariant p. A switch from linear to nonlinear fitting resulted in significantly smaller val ues of D (D-1 greater than or equal to D-nl). Oily waste sludge incorp oration resulted in marked reductions in D-1 (R(2) = 0.88) or D-nl (R( 2) = 0.88). The results show the values of D obtained using nonlinear fitting and scale-variant p are accurate and smaller than those obtain ed using nonlinear or linear fitting or scale-invariant p or a combina tion of the latter three.