Modeling of Infiltration Characteristics by the Modified Kostiakov Method: A Case Study in Thuong River Alluvial Soil in Vietnam

The purpose of this study was to apply the modified Kostiakov method to determine the soil infiltration rate and permeated water amount of Thuong River alluvial soil for orange plantations in Lang Giang district, Bac Giang province, Vietnam. The soil particle size ranged from 0.02 to 2.00mm mainly found in the surface horizon (>77.7%). The soil was slightly acidic in the surface horizon, and highly acidic in the subsurface horizons (pH_KCl from 3.42 to 4.79). The organic matter content of the surface horizon was mederate, while it was very low in the other horizons. The total nitrogen (N) content was low (0.15%) in the surface horizon and very low in the subsurface horizons (0.02-0.06%) while the available N was medium. The total phosphorus (P) content in the surface horizon was high (0.4%) and medium in the other horizons. Available P in the surface horizon was high (18.6mg per 100g soil) and decreased in lower depths to only 0.3mg per 100g soil in the deepest (5^th) horizon. The total and available potassium measurements were very low. A filtration characteristic model was developed by using the modified Kostiakov method for alluvial soil. The constant values a, a, and b of the equation y = at^a + b were 0.8035, 0.758, and 0.00346, respectively, which were smaller than 1. The average percentage difference between the actual and calculated values by the model was only 0.141%, indicating that the calculated values can accurately predict the actual data measurements in the field.