Corn and Wheat Response to Topsoil Thickness and Phosphorus on Reclaimed Land

Stripmining of coal drastically disturbs agricultural land and may alter many of the plant‐soil‐water relationships of undisturbed land. Plots were established on leveled moderately sodic clay loam mine spoil to evaluate topsoil thickness and P on crop production and soil moisture in a semiarid environment. A nonsodic sandy loam topsoil was replaced on the spoil at thicknesses of 0.05, 0.15, 0.30, and 0.60 m. Prior to topsoil placement, P was broadcast on the leveled spoil at rates of 0, 34, and 100 kg P ha −1 . Phosphorus at rates of 0, 11, and 34 kg ha −1 was applied annually for 4 yr to plots seeded to hard red spring wheat ( Triticum aestivum L.) using a drill attachment and by banding to corn ( Zea mays L.). In the last 2 yr, P broadcast rates of 0, 12, and 12 kg P ha − 1 on wheat and 0, 18, and 18 kg P ha −1 on corn were substituted for the drilled and banded P treatments. Corn silage and wheat grain yields in most years were significantly higher on 0.15‐, 0.30‐, and 0.60‐m topsoil compared to 0.05 m. The clay loam spoil was not as drought prone as the sandy loam topsoil and therefore, as the thickness of topsoil increased, the ability of the profile to continuously supply water to the growing crop decreased. The relationship between wheat yield and total water use was similar to undisturbed soils in the Northern Great Plains. Responses of wheat and corn to the one time broadcast application of P to the topsoil‐spoil interface or annual applications were generally small and occurred at the low rate of P.