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PAT 2012; 8 (1): 105-110: ISSN: 0794-5213; Eneje and Kalu,: Relationship between Aggregate Stability…...108Table 1: Physicochemical properties of plantation soils with depthPlantationtypeDepth of ofSampling(cm)Sand/clayratioOrganicMatter(%)AggregateStability(%)ExchangeableSodium percentage(%)Rubber 0-15 1.13 5.34 0.72 2.03Rubber 15-30 0.72 2.36 0.8 1.58Pineapple 0-15 1.94 2.34 0.26 4.31Pineapple 15-30 1.68 1.71 0.28 3.88Oil palm 0-15 0.89 5.09 0.44 3.47Oil palm 15-30 0.52 3.89 0.29 4.66FLSD (0.05)P 0.32 0.79 0.25 1.7D 0.26 0.65 N.S N.SPXD N.S 1.1200.35 N.SGenerally for all the plantation type studied, aggregate stability was seen todecrease with depth except in the pineapple plantation soil. This may be due to the factthat the pineapple soils were mostly sandy (pineapple thrives well in well drained sandysoils). This observation also supports the report that organic matter had a strongrelationship with the sand/clay ratio, as organic matter additions increased aggregationregardless of cation composition, as observed in this study (Figure 1), this observationagrees with an earlier report of Aldrich and Martin, (1954).The pineapple soils had the highest sand/clay ratio which reduced with depth in allthe plantations sites considered. The high sand/clay ratio in the pineapple soil probablyled to a low aggregate stability, this was also reported in a study by Kay and Angers,(1999) suggesting that clay content in the soil affected its aggregate stability. Theseobservations therefore supports the inverse relationship between sand/clay andaggregate stability observed in this study (Figure 1), as an increase in sand/clay ratio ledto a decrease in the aggregate stability in all the plantations considered. Theexchangeable sodium percentage was highest in the oil palm within the 15-30cm depth.This may be due to the high percentage of sodium in the exchange site relative to otherexchangeable cations. The exchangeable sodium percentage of soils decreased withdepth except in oil palm soil where it increased with depth. There was an inverserelationship between the exchangeable sodium percentage and the aggregate stability(Figure 1), this observation is supported by the report of Aldrich and Martin, (1954)that, as aggregate stability decreases the exchangeable sodium percentage increases.