Spatial Series Analysis of Horizontal Cores to Characterize Tracer Patterns in Soil Profiles

Surface topography, plant canopy, plant root distribution, and soil preferential flow paths cause variability in downward movement of agrichemicals in soil. To better understand this variability, tracers are often applied to the soil surface and their signatures (concentration patterns) are examined. To characterize Br− signatures within a Crete silt loam soil (fine, montmorillonitic, mesic Pachic Argiustoll), potassium bromide was applied to the soil surface at 200 kg ha−1. Four sets (two sets in June and two sets in August) of four 6.1‐m horizontal cores were taken in a vertical plane, perpendicular to corn plant rows at 20‐, 40‐, 80‐, and 120‐cm depths. Each 6.1‐m core was divided into 120 5.1‐cm sections and analyzed for Br−. Spatial series analyses were used to identify deterministic and combined deterministic‐stochastic models that described the cyclic nature of Br− concentrations at each depth. Periods for these sinusoidal cycles generally corresponded to the distance between plant rows or the distance between the wheel tracks of field equipment.