Optimization of silt, sand and clay contents for aggregate formation and stability of sandy tailings using organic amendments
1996
A.M. Mokhtaruddin | S. Zulkifli
Previous studies on the addition of organic amendments to sandy tailings have failed to demonstrate positive responses to aggregation and stability of these soils. To prove this point for sandy tailings ( 99% sand) and experiment was conducted to see the effect of dried palm oil mill effluent (POME) on aggregation and stability of these soils. Results showed that the additon of POME cake even at the rate of 100 t haE-1 only improve aggregation and stability slightly. Of more important is that the extent of aggregation was very low (% agg. 2 mm was only 6%). It is thought that the low content of very fine sand and silt in these soils, both amounted to 5.8% and the absence of clay are the cause of this. Following the first study, a second experiment was conducted to see the effect of different amounts of very fine sand, silt and clay on the aggregation and stability of sandy tailings by POME. In this experiment, sandy tailings were mixed with different proportion of slime (slime is to provide the necessary fine materials) and then treated with POME cake at the rate of 20 t/haE-1. results showed that mixtures of 20-45% slime and 55-80% sand which correspond to 7-15% clay and 2-25% silt + very fine sand gave 13-40 fold increase in % aggregation and 4.5-6.5 fold in stability over the control. In conclusion for physical improvement of sandy tailings ( 99% sand) using organic amendments, at least 7-15% clay and 20-25% silt + very fine sand are needed. Their presence enhances aggregate formation and stability which have a great implication on utilization of these marginal soils for crop production.
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