Rapid Changes in Sandy Soils under Intensive Agriculture in Wisconsin

We have quantified the effect of land use change by measuring soil physiochemical changes in sandy soils under intensive agriculture, grasslands, and pine forest in the central sands plain of Wisconsin, USA. The soils under agriculture (corn, potato, soybeans, and peas) are irrigated (280 mm yr –1 ), limed, fertilized, and leveled. Soil observations were made in 82 pedons, and soil horizons, texture, and pH were measured. The soils are all very sandy and somewhat excessively drained. In all pedons, sand percent increases with depth from 88 to 98%; silt content is around 8% until the C horizons where the silt content decreases to 2% on average. Coarse fragments increase at 60 to 100 cm and decrease below 140 cm. Topsoil thickness under agriculture ranged from 20 to 42 cm (mean 28 cm), topsoils under forest ranged from 3 to 27 cm, and topsoils under grassland ranged from 14 to 26 cm. It was found that the soils under agriculture are less acidic, have thicker topsoil horizons, and have slightly more clay, possibly as a result of enhanced mineral weathering. These sandy soils have changed in three decades from Udipsamments and Hapludalfs into Argiudolls and Hapludolls, while some soils have changed from Hapludalfs into Udipsamments. Topsoil depth changes in the Wisconsin Central Sand Plain are the result of intensive agriculture.