Hydraulic Conductivity and Aggregation of Fine-Textured Soil Under Intensive Cattle Grazing

Abstract

Information on hydraulic conductivity and macro- and micro-aggregate stability is needed for evaluating the ease with which soils slake and erode when in contact with water. In fine-textured soils, it will provide information on ponding of water and decrease in hydraulic gradient with wetting. This study was conducted to determine changes in hydraulic conductivity and macro- and micro-aggregate stability of a fine-textured submerged soil under intense cattle grazing for 15 years. Hydraulic conductivity of the cattle grazing soil ranged from very slow (0.46 cm hr -1 ) to slow (19.56 cm hr -1 ) in the top 0-25 cm depth, and attained near zero permeability (0.15 cm hr -1 ) before 75 cm depth. Permeability was rapid (21.1 to 30.06 cm hr -1 ) throughout the profile in the non-cattle grazing soil. Organic residues from cattle grazing activities raised the soil total organic carbon to as high as 72 g kg -1 in the top 0-25 cm depth. Wet trampling of organic residues from cattle excreta induced greater soil swelling and loss of soil strength resulting in low aggregated silt and clay (ASC) and clay flocculation index (CFI) within the 25-75 cm depth. Clay dispersion index (CDI) showed significant negative (P < 0.05) relationships with mean weight diameter (MWD) of water stable aggregates and saturated hydraulic conductivity (r = -0.631 and -0.596 respectively). Soil parameters controlling water storage and infiltration in such soils need to be increasingly studied to increase the area of land available for crop production and reduce soil erosion since such soils usually have high chemical fertility status.