3-DIMENSIONAL MOVEMENT OF WATER AND PESTICIDE FROM TRICKLE IRRIGATION - FINITE-ELEMENT MODEL

A flow model described by cylindrical coordinates r, phi, and z was used to simulate water and pesticide movement from a trickle irrigation emitter. The model considered unsaturated, non-steady flow in a multi-layered soil, taking into account a reactive and degradable pesticide. Linear and first order equations were used to describe the adsorption and degradation of the pesticide, respectively. The finite element technique was used in solving the non-linear differential equations in conjunction with a finite difference scheme to solve the time dependent part of the equations. Linear shape functions were used to approximate the different parameters in the differential equations. The model was validated by applying the nematicide Nemacur, [ethyl 3- methyl-(methylthio) pheny(1-methylethyl) phosphoramidate], through a trickle irrigation system to the root zones of peach trees.