Aggregate stability changes in a semiarid soil after treatment with different organic amendments

Structural stability of soils is one of the most important characteristics related to soil degradation in semiarid areas. Organic additions can considerably improve soil structure and prevent soil degradation. In this experiment the effectiveness was compared of four types of organic amendments on the improvement of soil structure. The four treatments are sewage sludge, fresh uncomposted urban refuse, composted urban refuse, and horse manure. The uncomposted urban refuse was the most effective in increasing soil stable aggregates. The higher doses of sewage sludge and compost also improved aggregation of soil particles. Horse manure did not significantly improve soil aggregation. A significant correlation (r = 0.955, ρ < 0.01) was found between fungal populations and stable aggregates. No significant correlations were found between stable aggregates in soil and the other parameters assessed. The organic treatments increasing soil microbial populations and promoting their activity appear to be very effective in improving soil structure.