Dredged Sediment: Application as an Agricultural Amendment on Sandy Soils

Periodic dredging of lakes and waterways generates large amounts of material, often stored indefinitely in extensive sediment basins. A proposed dredging project in the Peoria Lake portion of the Illinois River will generate an abundant amount of sediments. This study proposed using sediments dredged from the Illinois River to enhance sandy soils as sediments often have high nutrient levels and physical properties that are desirable for agricultural production. Dredged sediments may greatly improve extensive areas along the Illinois River that have sandy soils with poor physical properties. We built research plots using Peoria Lake sediment at 0, 7, 15, and 30 cm thicknesses applied to the surface of Plainfield sand. Corn and soybean plants were grown on the plots for four years. An analysis of chemical and physical properties of soil treatments revealed a significant improvement in water holding capacity, cation exchange capacity, and the nutrient content of the soil. Animal damage to plants in the experiment, including the excavation and consumption of seeds after planting and grain before harvest, complicated the interpretation of treatment effects. However, a significant plant response was observed when the sediments were applied. In corn, higher vegetative growth and grain yields were observed in plots treated with surface-applied sediment. With soybeans, vegetative growth was greater on sediment plots than on corn plots; however, treatment effects were not as dramatic as with corn, and the highest soybean yields were observed in the 15 cm sediment plots. Concentrations of metals in soils and plant tissues were within levels considered to be normal. However, molybdenum (Mo) levels in soybean grain were found above levels considered to be safe for livestock fodder if the copper (Cu) content was low in ruminants’ diets. High Mo levels are a common problem in certain US soils, easily solved by providing feed supplements to ruminants. Polychlorinated biphenyl (PCB) levels in soybeans were below the detection level (17 μg kg-1) for four of six samples from the sediment plots. The other two had levels of 21 and 22 μg kg-1. We concluded that Peoria Lake sediments hold promise as a topsoil additive when applied to sandy soils.