The effect of changing soil bulk density with depth on wetting front advance under a trickle line source

Among the factors affecting the movement of water in the soil are soil properties (structure and texture). The rate of components of soil minerals and organic material has an effect on its bulk density. As the surface soil has organic matter more than subsurface soil in general, the bulk density increases with soil depth, so the research aims to study the effect of changing soil bulk density with depth on wetting front advance under a trickle line source. The experimental work included a nine laboratory tests for monitoring the advancement of the wetting front with time, The water advance and water distribution measurement are carried out for three cases of the soil profile with the change of bulk density along soil depth (0.00923,0.00462,0) gm/cm 3/cm: first case with the soil changed bulk density from 1.2 gm/cm 3 at the soil surface and gradually to 1.8 gm/cm 3 at a maximum depth of the profile, the second case with the soil changing bulk density from 1.5 gm / cm 3 to 1.8 gm / cm 3, and the third case homogeneous soil with bulk density 1.2 gm / cm 3, and using three application flow rates 1.3,2.6,3.9 cm 3 / min / cm. The study showed that with the increase in the change of bulk density along soil depth there is a small increase in horizontal advance and almost non-existent increase in vertical advance while they are clear and tangible in diagonal advance. It also showed that the amount of the increase in the vertical advance is greater than in the horizontal advance and be could be in diagonal advance when increasing the application flow rate, and all of the horizontal advance, vertical advance and the diagonal advance of the wetting front increase with the decrease of the application flow rate when applied in the same volume of water.