SPATIAL VARIABILITY IN THE UPPER SOIL LAYER OF A NO-TILL FIELD USING A SMALL-SCALE DYE EXPERIMENT

Abstract

Small-scale (33 cm by 33 cm) dye experiments were performed to evaluate the spatial variation of infiltration by evaluating dye distribution within the upper 10-cm soil depth of a well-established no-till corn field. The variation of infiltration was estimated by measuring the dye concentrations in the soil samples obtained from the 0- to 3-cm, 3- to 6-cm, and 6- to 10-cm depths of the infiltration test volume (10,890 cm 3 ). Contour maps of dye concentrations were prepared for each soil layer and used to estimate the percentage of the infiltration area that had a higher than average dye concentrations. Results indicate that (1) statistically, the dye concentration in the upper soil layers (0 to 3 cm) have a higher average dye concentration with less variability than the middle and lower soil layers; (2) the majority of the infiltration solution appeared to pass through 23% of the infiltration area; and (3) the spatial distribution of the dye concentrations are highly heterogeneous. The statistically and spatially heterogeneous dye distribution suggests that under ponded infiltration conditions in no-till systems, preferential flow may be the primary mechanism affecting the distribution of infiltrating water throughout the 0- to 10-cm depth. The heterogeneous dye distribution suggests preferential flow was established in the 0- to 3-cm layer for most of the tests.