Contrasts in the physical properties of three soils of an Alfisol catena in Sri Lanka

Abstract
The agricultural implications of differences in soil physical properties along an Alfisol catena were evaluated. The properties studied were steady infiltration rate, saturated hydraulic conductivity (Ks), available water capacity, bulk density, field air capacity and soil texture. The catena consisted of Rhodustalfs, Haplustalfs and Tropaqualfs. A significant increase in clay content downslope was the major factor influencing the changes in associated soil physical properties. Steady state infiltration rate decreased significantly downslope. The Rhodustalfs occurring at the crest showed a steady infiltration rate of 1.91 cm/h which is optimum for surface irrigation. This decreased to 0.68 cm/h in the Haplustalfs and to 0.29 cm/h in the Tropaqualfs at the bottom of the catena; the last showing suitability for rice cultivation. Ks decreased downslope showing poor soil drainage and aeration in lower horizons of the Haplustalfs and Tropaqualfs. Available water increased downslope from 97 mm/m in the Rhodustalfs to 106 mm/m in the Haplustalfs and 122 mm/m in the Tropaqualfs. These results indicate the importance of the catena approach for soil characterization when planning agricultural projects.

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