PERTANIKA JOURNAL OF TROPICAL AGRICULTURAL SCIENCE

The effect o f skeletal materials (silt and very fine sand) and clay on aggregate formation and stabilization of organically amended sand tailings (99 VO sand) was investigated. In this experiment, sand tailings were mixed with different proportions o f slime ( slime contains 37 Vo silt + very fine sand and 33% clay) and then treated with palm oil mill effluent ( P OM E ) cake at the rate o f 10.5 g o f P OM E cake per 1200 g o f sand-slime mixture. The mixtures were incubated for 2 weeks and then air-dried. The extent o f aggregation o f the samples was determined by dry sieving, and the aggregate stability by wet sieving. The addition o f silt + very fine sand and clay improved aggregation and aggregate stability o f the sandy soils. The optimum amount o f clay required achieving a good aggregation and aggregate stability for the amount o f organic matter added is 2 5%, where the increase in stability was seven-fold over the control. With slime, which contains 33% clay, this amount o f clay can be achieved from a mixture o f 75% slime -I- 25% sand tailings. This mixture contains 32% skeletal materials.