Water infiltration in soils of variable bulk density with depth

Abstract

Water infiltration in soils is one of the most important factors that must be considered in designing optimal irrigation systems. A total of twelve laboratory experiments were carried out to assess the influence of bulk density variation with depth on infiltration depth, infiltration rate, and wetting front depth. A cylindrical soil profile of 11.43 cm diameter and 40 cm height was prepared by compacting every 10 cm of it with different bulk densities. Two types of soils (sandy loam and clay) and six sets of bulk density variations with depth (three of them were increasing and the others were decreasing) for each soil were considered. Three empirical models were developed to predict the depth of infiltration, advance of wetting front, and infiltration rate based on time, bulk density of the upper layer, bulk density variation, and percentages of clay, silt, and sand with a high coefficient of determination. The results revealed that bulk density variation has a slight effect on water infiltration while bulk density of the upper layer has the highest effect on water infiltration. It was found that decreasing bulk density has a higher impact on infiltration than increasing bulk density, and the clayey soil is more sensitive to bulk density variation than sandy loam soil. A decrease of 7.8% and an increase of 23.66%, 25.8% were noted in the rate of infiltration, depth of wetting front, and depth of infiltration, respectively for clayey soil with bulk density of the upper stratum of 1.5 g/cm³ and decreasing bulk density of 0.82% after 7 h of infiltration compared to those with no bulk density variation.