AGGREGATE STABILITY CHANGES IN A SEMIARID SOIL AFTER TREATMENT WITH DIFFERENT ORGANIC AMENDMENTS

Structural stability of soils is one of the most important characteris tics 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 org anic amendments on the improvement of soil structure. The four treatme nts are sewage sludge, fresh uncomposted urban refuse, composted urban refuse, and horse manure. The uncomposted urban refuse was the most e ffective in increasing soil stable aggregates. The higher doses of sew age sludge and compost also improved aggregation of soil particles. Ho use manure did not significantly improve soil aggregation. A significa nt correlation (r = 0.955, p < 0.01) was found between fungal populati ons and stable aggregates. No significant correlations were found betw een stable aggregates in soil and the other parameters assessed. The o rganic treatments increasing soil microbial populations and promoting their activity appear to be very effective in improving soil structure .