Goodness of fit of three infiltration models of a soil under long-term trial in Samaru, Northern Guinea Savanna of Nigeria

Good strategies for water conservation, runoff or flood control and erosion management can be achieved by proper understanding of soil water infiltration characteristics. Three infiltration models Kostiakov’s (1932), Philip’s (1957) and Horton’s (1940) were used to evaluate the infiltration characteristics of soils in a long-term fertilizer experiment in the Northern Guinea Savanna Agro Ecological zone with regard to the effects of long term land use and soil management. A double ring infiltrometer was used to conduct infiltration measurement on ten plots having different combination of Dung (D), Nitrogen (N), Phosphorus (P), and Potassium (K) fertilizer treatments. Thus, the treatments combinations were DNPK, DN, DK, DP, D, NPK, N, P, K and CT (no fertilization). Soils were predominantly sandy loam and bulk density and organic carbon were significantly influenced by the fertilizer combinations. Linear least sum of squares was used to obtain the model fitting parameters. Measured infiltration rates for plots that received dung (singly or in combination with mineral fertilizer) were significantly higher (p<0.05) than for the CT plots. Kostiakov’s and Philip models showed good agreement with measured infiltration due to large R2 (0.9956 and 0.986) recorded, respectively except Horton’s model, which gave low regression coefficient between measured and calculated data. Based on R2 values obtained from comparing measured and calculated cumulative infiltration, Kostiakov’s and then Philip’s equations provided best predictions over Horton. Fitting parameters obtained are suggested for use of site-specific or management-specific solutions of infiltration-related application. Further work is required to obtain reliable fitting parameters for Horton’s infiltration equation of the trial field.   Key words: Kostiakov, Philip, Horton, infiltration characteristics, DNPK plots.