Effects of Fallow Length on Organic Carbon and Soil Fabric of Some Tropical Udults

Abstract

AbstractSoil samples representing eight different ages of forest regrowth (0–50 yr following clearing) from fields in a pineapple slash and burn agricultural system were collected for organic carbon (OC) analysis and study of soil physical properties. The OC content of the surface soils decreased for 10 yr following clearing, then gradually increased close to the original level after 50 yr. Major micromorphological differences were apparent in surface horizons as a function of OC content. Soils with higher OC contents were more strongly aggregated and have more visible porosity than those with less OC. Bulk density and OC are statistically, significantly, negatively correlated (r2 = 0.64, p < 0.05), for combined data from all four representative pedons. Particle size distribution had a large effect on subsoil micromorphology. Argillic horizon fabric within the finest grained pedon was mostly mosepic with few discrete cutans suggesting that in situ weathering is a dominant clay forming process. Coarser textured pedons had well‐oriented argillans in the skelvosepic to vo‐masepic fabric of the argillic horizons. The short‐cycle slash and burn methods studied here have no observable effects on the micromorphology of the argillic horizons.