The Use of Fly Ash to Determine the Extent of Sediment Transport and Deposition on a Nearly Level Western Illinois Landscape

Most Illinois soil landscapes are nearly level and composed of somewhat poorly drained soils on slightly higher convex landscape positions and poorly drained soils on concave landscape positions. These soils are commonly on less than 1% slopes and are not thought to have water erosion and sediment deposition problems. A plot area near Monmouth, Illinois, was selected for study. The fly ash and soil organic C (SOC) content of Muscatune and Sable soils were determined. The crop sequence was corn and soybeans for the last 27 years, and plot area had been cultivated for the last 130 years. There is no tile drainage in the plot area. The primary objective of this research was to determine the extent Muscatune soil on 1% slope was eroded in the past 100 to 130 years of cultivation. The fly ash and SOC-rich sediment being transported to and deposited on the adjacent Sable soil in the same plot area were measured using a fly ash method. Fly ash is particulate matter resulting from high-temperature combustion of coal since 1910s and can be used as a time marker in upland soil erosion and depositional studies. For the 0- to 0.50-m layer, the Sable soil fly ash content is 19% higher and the SOC is similar (4% higher) to those of the Muscatune soil. The erosion rate, using the fly ash method, was 4.35 Mg ha(-1) year(-1), which was higher than the calculated RUSLE2 erosion rate of 3.3 Mg ha(-1) year(-1). Approximately 0.06 m of the thickness difference of 0.21 m between Sable and Muscatune A horizons was the result of erosion of the Muscatune soil and deposition on the Sable soil. The remaining difference was as a result of higher water table and saturated soil conditions for long periods.