Evaluation of soil hydraulic parameters for soil water distribution models under drip irrigation

Abstract

The transient analytical solutions for water distribution from point source are dependent on the soil parameters a from Gardner equation, i.e., k(h) = K_s e^ah and the linearization parameter k=dK(q)/dq assumed constant in the derivation of these solutions. Errors in obtaining these parameters result in failure of the solutions. The objective of this work was to evaluate the parameter a and k at different locations in the wetted volume under an isolated and a cyclic infiltration process. Matric potential data were collected in several positions of the wetted volume in two situations: (i) beginning of irrigation until steady-state, i.e., only during infiltration process, and (ii) during two irrigation cycles involving infiltration and redistribution processes. The results showed that a and k parameters vary at different locations of the wetted volume related to the dripper according to the water regime at these locations. The use of inverse method for obtaining these parameters requires matric potential data from infiltration and redistribution during at least two irrigation cycles.