Using Soil Water Content Sensors to Characterize Tillage Effects on Preferential Flow

Because groundwater is a source of drinking water for many people, there is great concern to protect groundwater resources. Preferential flow through the unsaturated zone is considered one of the main contributory factors in groundwater pollution, which is influenced primarily by soil heterogeneity and management practices. To characterize the degree of preferential flow, the soil water content dynamics during short- and long-term periods in the shallow zone (0-40-cm depth) of two plots with no-till (NT) and conventional tillage (CT) soil management practices were investigated for 2 yr using soil water sensors placed horizontally in a rectangular grid along transects across crop rows. Analysis of response times and water content changes during rainfall events confirmed the existence of short-term preferential flow at the site and that macropores and heterogeneities in soil hydraulic parameters in the shallow zone may have contributed to infiltration into the deeper layers in the NT plot. In the longer term, the pathways of infiltration and redistribution were different between the growing and non-growing seasons; however, these differences were relatively stable in both plots during the 2-yr study period.