ABSTRACT

 Organic amendments can affect soil properties. The predictive power of selected water infiltration models in organic amended soils were evaluated. Ten (10) infiltration models consisting of five (5) empirical (Philip (PH), Kostiakov (KT), Modified Kostiakov (MK), Kostiakov-Lewis (KL) and Natural Resource Conservative Service (NRCS)), Three (3) physically based (Green-Ampt (GA), Smith-Parlange (SP), Talsma-Parlange (TP)) and two semiempirical ( Swartzendruber (SW) and Horton (HT)), were evaluated for soils amended with cow dung, poultry litter and Pig dung. The study was carried out at University of Uyo experimental plot at Uyo, Akwa Ibom. The field was ploughed to a depth of 20cm in order to mix the manure with the soil. Soil samples were taken from each strip, and the tests were repeated two weeks, four weeks and six weeks after manure application. Amendment with Cow dung, poultry litter, and pig dung increased cumulative infiltration by 56.05%, 36.43, and 2.6% respectively. The statistical model was used to evaluate the model performance. The coefficient of determination R2 between the models simulated cumulative infiltration and field measured cumulative infiltration ranged from 0.931 to 0.998. The value ofthe modelling efficiency (E) index ranged from -0.048 to 0.998 while the Mean Absolute Error (MAE) ranges from -0.955 to 5.454. The values of the coefficient of residual mass (CRM) ranged from -1.320 to 0.572. Seven models (NRCS, Philips, Kostiakov, Kostiakov-Lewis, Modified Kostiakov, Talsma-Parlange and Swartzendruber’s model) under-predicted while three models (Green-Ampt, Smith-Parlange and Horton) over-predicted cumulative infiltration. The NRCS’s model had the overall best performance, while Kostiakov model had best performance amongst the empirically based models.The Talsma-Parlange’s model had the best performance in the physically based models, while Horton’s model had the best performance in the semi-empirical group. The whole NRCS model was found to be most appropriate for cow dung, Poultry litter, and the Control, while Kostiakov model was found to be most suitable in the Pig dung amended soil